designing with engineering plastics

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Designing withengineering Plastics



Licharz on the web

Certified q ua lity m a na g eme nt a ccord ing t o DIN EN ISO 9001 : 2000DIN EN ISO 9001:2000

Certificate No 01 100 040034



C o n t e n t s

Contents

Polyamides (PA) 6-10

Oilamid® 11-13

Calaumid® 612 / Calaumid® 1200 14-15

Calaumid® 612-Fe / Calaumid® 1200-Fe 16

Polyacetal (POM) 17-19

Polyethylene terephthalate (PET) 20-21

Polyethylene (PE) 22-24

Polypropylene (PP) 25-26

Polyvinyl chloride (PVC) 27-28

Polyvinylidene fluoride (PVDF) 29

Polytetrafluoroethylene (PTFE) 30-31

Polyetheretherketone (PEEK) 33

Polysulphone (PSU) 34

Polyether imide (PEI) 35

Tolerances 105-113

Machining guidelines 114-118

Physical material standard values and chemical resistances 119-133

Information on how to use this documentation / Bibliography 134

Foreword – Engineering plastics as design materials 4

Material overview 5

Structure and properties of plastic 36-43

Behaviour in fire 44-45

Resistance to radiation and weathering 46-47

Storage information 48

Plastic friction bearings 49-60

Plastic sliding panels 61-64

Plastic castors 65-75

Plastic rope pulleys 76-85

Plastic gear wheels 86-100

Plastic spindle nuts 101-104



Eng ineering plastics are b ecoming increasing ly popu lar in ma chine a nd pla nt con struction a s designeng ineers recogn ise their advan ta g es an d econo mic sig nifica nce.

The use a nd de velop men t o f ma te ria ls is subject t o con tinuo us cha ng e. This a lso a pplies to pla stics.Man y machined part s tha t w ere man ufa ctured exclusively from convent ional meta ls just ten yea rs

ag o a re now b eing ma de from mod ern engineered plast ics.

We can expect th is chang e to continue in the f uture – perhaps at a n even fa ster pa ce than w e ha veexperienced to da te . This chang e can b e a t t r ibut ed t o t he eno rmous ri se in the num ber o f en-g ineer ing plas t ics ava i lab le a long w ith the i r man y di f ferent mod if ica t ions , cha racter ist ics andpossible a ppl ica t ions . Due to th e i r speci f ic propert ies , man y plas t ics a re eq ua l or superior inma ny w ays to convent iona l design ma ter ia ls. In ma ny cases, eng ineer ing plast ics have a l readyreplaced conventiona l mate ria ls due to the ir superior perfo rmance properties.

The ma in advan ta g es of eng ineering plastics in compa rison t o conventiona l meta ls are: w eight red uc-tion, resista nce to w ear, go od vibrat ion a bsorption an d t he fa ct t hat plast ics are easier to machine.Add itiona lly, the ir high level of chemical resista nce, the increa sing th erma l sta bility o f several types of

plastic an d improved recycling po ssibilities a re furth er positive arg umen ts for choo sing eng ineeringplastics.

The t ask of d esig n eng ineers w ill increa sing ly be t o f ind a n o ptima l mat erial fo r a specific a pplica-tion w hile keeping production costs dow n. Often t here is a lack of a w areness regarding t he a ctualvolume prices of plast ics compa red t o convent ional met al ma teria ls. Even high q ua lity mo dif iedpolyamides ca n be less expensive tha n ma ny types of m eta ls. In ad dition, the much low er qua ntityof chips whe n plastics are ma chined is a not her fa ctor tha t influences the p rice /performa nce ratioin compa rison t o me ta ls.

The experience t ha t LICHARZ ha s ga ined d uring t he last 40 yea rs in m a nuf a cturing, pro cessingan d ut i liz ing eng ineering plast ics for ma chine a nd eq uipment design, aut omo tive industry appli-cat ions and ot her a reas ha s mad e LICHARZ on e of th e lead ing comp a nies in this industry in Euro-pe (w orld w ide???). Over the yea rs, w e ha ve come t o fo cus on a pplication s tha t a re subject to slipa nd w ea r stresses an d ha ve achieved extensive success.

The m a jority o f semi-finished prod ucts as describe s in t his do cumen t, especially a ll varian ts of castpolyam ides, and f inished pa rts, are produced in our plant or man ufa ctured b y us on cutt ing e dg eCNC con tro lled ma chines.

In o rder to ma ke it e as ier for d esign eng ineers an d users to de t ermine w hich plas t ic is best f orth eir specific ap plicat ions, w e ha ve summa rised our experience in th e fo rm of m a te ria l de scription san d d esign an d ma chining informat ion in this brochure.

Please do no t hesita te t o conta ct us w ith a ny questions you ma y have.

3rd ed ition, July 2004

Foreword

4



Material overview

The m ost import an t eng ineering plastics are

Polyamide (PA)

Polyacetal (POM)Polyethyleneterephthalate (PET)

Man y differen t ma terial modifica tions of the se eng ineering pla sticsare used in component s that are subject to sliding a nd w ear load s.

Other ma terials are on ly used occasiona lly fo r sliding app licationsan d ma inly for applicat ions w here th ere is chemical dema nd.The se includ e

Polyethylene (PE)

Polypropylene (PP)

Polyvinylchloride (PVC)Polyvinylidenefluoride (PVDF)

Polytetrafluoroethylene (PTFE)

High-performance plast ics are a not her group of modern mat eria ls that

are cha racterised b y their hig h level of rigidity a nd sta bility at hightem perat ures. The d isad vant ag e is the high price, w hich in some ca sescan b e a s much a s 30 times the cost o f en gineering plastics.Hig h-perf orma nce plastics includ e

Polyetheretherketone (PEEK)

Polysulphone (PSU)

Polyether imide (PEI)



Polyamides (PA)



P A

Polyam ides are subdivide d int o va riou s ba sic types. The m ost impo rta nt a re PA 6, PA 66 a nd PA 12.The differences in ph ysical prope rties are in th e compo sition an d structure o f t he m olecule cha ins.

In the manufacture o f semi- f in ished products , a d is t inct ion i s made between moulded andextruded materials.

The key properties of polyamide are:

• Hig h me chanica l sta bility, ha rdness, rigidity a nd to ug hness• Hig h mechan ica l da mping propert ies• Goo d f a t igue resista nce• Very high w ea r resista nce• Go od sliding a nd emerg ency running properties• Goo d machining properties

Because of t he hig her crysta l l ini ty , semi-f inished prod ucts manu fa ctured b y casting ha ve much

bet ter physical propert ies tha n extruded p olyamides.

Extruded Polyamides

Polyamide 6

i s the best know n extruded po lyam ide . PA 6 o f fers a g oo d comb ina t ion o f mecha nica l s tabi li ty,impact resis tance an d d am ping , but compared to PA 6 G it ha s much low er w ea r res is tance ,

ab sorbs more moisture an d h as less dimensional stab i li ty. Applications: part s tha t a re subject toshock and impact , ge ar w heels, hammer hea ds.Colour: na tura l, black

Polyamide 66

is used in sma ller app lication s. Com pa red t o PA 6 it is ha rder a nd is mo re resista nt to w ea r, how e-ver, it do es ha ve less impa ct resista nce. Applica tion s: friction b ea ring s, sliding pa nels. It h a s simila rmecha nical prop erties to PA 6 G, w hich is much less expensive a nd is g enera lly used instea d of PA66.

Colour: natural

Polyamide 12

ha s very goo d impact b eha v iour, it i s to ugh an d, becau se o f i t s very low w a t er ab sorpt ion , i t isdimensionally stable. I t is avai lable in small quanti t ies as semi-f inished products, but is notg enera lly considered fo r construction a pplication s due to its hig h price (3-4 times more e xpensivet ha n PA 6).

Polyamides (PA)



P A

The so-called m on om er mo ulding pro cess, in w hich semi-finished prod ucts are creat ed b y mea nsof a contro l led chemica l react ion , i s a s igni f icant improvement compared to convent iona lextrusion o r injection m oulding processes and is especia lly impo rta nt f or th e perfo rma nce of t hisma terial. Typical physical prope rties a re improved in a ta rget ed ma nner.

Range of cast polyamide materials

PA 6 G

Cast polyamide for components in machine and equipment designs tha t a re subject to wear(sta nda rd qua lity).Colours: na tu ral, black, blue

Oilamid®

PA 6 G w ith integ rat ed lubricat ion, self-lubricating effe ct, improved w ea r resista nce.Colours: black, yellow , na tura l

PA 6 G/WS

Essent ia l ly simi la r t o t he s tand ard q ua l ity b ut b e t t er pro tected w i th a therma l sta bi liser ag a instthermal-oxida tive deg rada tion.Colour: natural

PA 6 G/MoS

Essent ially similar to t he sta nd ard q ua lity, but th is type h as a hig her deg ree of crysta llinity du e tomolybde num sulphide constituents.Colour: black

Calaumid®612Co-polyamide ba sed o n PA 6/12-G w ith hig her impa ct a nd shock resista nce, less w at er a bsorptiona nd improved creep resistance compa red t o pure PA 6 G.Also a vailab le as Ca laum id® 612-Fe w ith a steel core (see sepa rat e ma te rial description).Colour: natural

Calaumid®

1200Cast polyamide ba sed o n laurin lacta m. Very go od impact be ha viour, to ug hness, excellent dimen-siona l sta bi li ty, low est w at er a bsorption, very go od creep resista nce, hydrolysis resista nce, go odchemical resista nce. PA 12 G is fa r superior to extrud ed PA 12 in every respect.Also a vailab le as Ca laum id® 1200-Fe w ith a steel core (see sepa rat e ma te rial description).Colour: natural

Cast polyamides



P A

PA 6 G is a be ige co loured, f i rm, hom og eneo us, s t ress-re lieved ma ter ia l w ith a h igh d eg ree o fcrysta l linity . Specif ic prope rties are a lso d eveloped t hroug h mo dif ica t ion, specia l sett ings andadditives.

Material properties

PA 6 G offers tried and tested characteristic material properties:

High abras ion and wear res is tance a t low to medium speeds compared to cas t i ron , s tee l orbron ze – especially under roug h cond itions (sa nd, dust).

Vibration and noise absorption

Prolong s the l ife o f m achine par t s throug h t he v isco-e las t ic ity o f t he plas t ic an d compl ies w i thenvironmen ta l requirements, e.g. no ise a bsorption via PA 6 G rollers, g ea r w heels, etc.

Low weight

With a specific w eig ht of 1.15 g/cm 3, PA 6 G only w eigh s a pprox. 13% of th e same volume ofbron ze, 15% of steel and 43% of aluminium, w hich mea ns less centrifuga l force and imba lance inrota t ing parts.

Chemical resistance

Aga inst w ea k acids an d alkalis as w ell as a ll conventional org an ic solvents.

Very good sliding properties

characterise PA 6 G a s a t radit ional f rict ion b ea ring ma teria l for ma chine pa rts that are subject toa lo t o f w ea r, such as bea r ing bushes, slid ing pan els, guide pa nels, gea r w heels an d sprocketw heels a nd ro l lers. Becau se of the low coeff icient o f f rict ion, lubrication is of te n unne cessary oronly an initial lubrica tion is required w hen t he pa rts are being insta lled.

Stability of physical properties

The prope rty values of PA 6 G a re inf luenced b y tempe ratu re an d m oisture. When t empera turesincrease or w at er is a bsorbed , tensile and compressive streng th a re reduced, mo dulus of elasticityan d ha rdness a re reduced, w hile impact resistance a nd e xpansion increa se.

PA 6 G



P A

Dimensional stability

This is a lso d epen de nt o n te mpera ture a nd m oisture. How ever, the h igh crysta l linity o f PA 6 Greduces moisture ab sorption considera bly. Wat er is on ly absorbed very slow ly. The ra te of ab sorp-tion reduces prog ressively w ith the dept h of penet rat ion.

Guiding values for moisture

Sat ura tion level in a sta nd a rd clima te (23° C/50% RH) de pen ding on type : 1.5 – 2%.Linear de fo rma tion d ue to mo isture a bsorpt ion: app rox. 0 .15 – 0.20% per 1% w at er ab sorbed .Linear def orma tion due t o te mpera ture chang es: a pprox. 0.1% per 10°C tempera ture difference.

Machining

PA 6 G can ea si ly be ma chined o n eq uipment tha t i s norma l ly used fo r meta l an d w oo d pro-cessing . To prevent def orma tion, ma te ria l sho uld be rem oved e q ua lly from a ll side s. If ma te ria l isto b e removed unevenly it i s recomm ende d th a t the w orkpiece be pre-w orked, annea led andstored f or 24 hours befo re the final processing w ork is ca rried o ut. Because of the not ch sensitivity

of plastics in gene ral, sha rp-edg ed t ransitions should b e a voided .

PA 6 G

Notch impact resistance

of polyamide 6 G a t low temperat ures

Notch impact resistance

of polyamide 6 G wi th d i f ferent w a t ercontents

Water absorption

o f po ly a mide 6 G in wa te r a t ro o mtemperat ure and sta nda rd climat e(Test p iece: sta nd a rd sma ll rod )

1

2

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N o t c h i m p a c t r e s i s t a n c e ( K J / m

2 )

Temp erat ure °C

10

9

8

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1

0100 101 102 103 104

W a t e r c o n t e n t [ % ]

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in wa ter a t room tempera ture

in standard climate

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N o t c h i m p a c t r e s i s t a n c e ( K J / m 2 )

Wat er conte nt (%)



Oilamid®



O i l a m

i d ®

Oila mid is a h igh-molecula r the rmop lastic ba sed on PA 6 G. Oilamid h a s a f ine crysta lline structurew ith high w ea r-resista nt an d self-lubricating properties. The hig h level of w ea r resista nce an d t heextraordinary sl iding properties are specif ica l ly developed by adding oi l , sol id lubricants andstabilisers.

Increased abrasion and wear resistance

The o il is ad ded bef ore t he po lymerisat ion process and gives the ma terial a self-lubricating eff ect.The coe ff icient of f rict ion is reduced by 50%, w hich ma kes Oilam id a n idea l desig n ma teria l fo rhighly loaded, s low moving , dry-running s l id ing e lements wi th up to 10 t imes more wearresista nce tha n unfilled po lyam ide. At slow to med ium speed s, a nd especia lly in roug h cond itions(sand, d ust), Oilamid ha s considera bly more ab rasion a nd w ea r resistance th an cast iron, steel orbron ze. Gene rally a pv facto r is given as a loa d limit fo r sliding e lements. Oilamid can w ork underhighe r loa ds an d speed s tha n PA 6 G. The inf luence on the level of sl iding a bra sion is subject t othe pa ramet ers o f t he surfa ce roug hness o f t he met a l lic ma t ing compo nent , sur face pressure ,s lid ing speed, s lid ing surface t empera t ure a nd lubrica t ion . Because o f i t s low coef f icient o ffriction, Oilam id ha s a low rat e of ab rasion an d is suitab le for d ry-running in special applications.

Vibration and noise absorption

Oilamid’s vibra t ion a nd noise a bsorpt ion pro long s the l ife o f ma chine pa r ts throug h t he v isco-elast icity o f t he plast ic and complies w ith environme nta l requirement s, e .g . noise a bsorption viaOilam id ge ar w heels an d rollers.

Excellent sliding properties

Due to i t s lubr ica t ion support ing e f fect , Oi lam id is becoming an importan t f r ic t ion bea r ingma teria l for ma chine a nd eq uipment pa rts such as bearing b ushes, sl iding pa nels, guide pa nels,g uide curves, gea r w heels a nd sprocket w heels.

Oilamid®

52 3 4 100,15 0,20,02 0,03 0,10,05 0,30,07 1,0

Polyamide 6 G

Oilamid®

0,4 0,6 0,8 1,5

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1,00

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B e a r i n g l o a d M P a



O i l a m

i d ®

Sliding abrasion as a function of the bearing load

Loa d w ithin the permissible pv ra ng e; lubrication: d ry-running;sliding surfa ce tempe rat ure: 80 ºC; surfa ce roug hness of t he steel count erpart Rz = 2µm

For sliding elemen ts tha t a re int end ed t o be u sed in dry-running a pplicat ions, it is recomme nd edtha t t hey a re given an init ia l lubrication to a l levia te b reak-in loa ding . The coeff icient o f slidingfriction o f Oila mid rema ins sta ble a s th e pressure increases. The stick-slip beha viou r is be tt er th a not her th ermoplastics.

Because o f t he low coeff icients of sliding frict ion, t he f rict ion hea t of Oilamid sliding elements islo w e r tha n o the r po ly a mide g ra de s , wh ich me a ns tha t the y ca n o pe ra te a t h ig he r l o a ds a ndspeeds.

Polyamide 6 G

Oilamid ®

5 6 7 8 9 10 11 12

0,11

0,10

0,01

0,02

0,03

0,04

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0,6

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POLYAMIDE 6 G

00,5 1,0 1,5

OILAMID®

Polyamide 6 G

Oilamid

30

20

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0

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50

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70

80

90

100

10 0,2 0,4 0,6 1,2 1,4 1,6 1,8 2,00,8

Coefficient of sliding friction of polyamide 6 Gand Oilamid

Frictio n ring ST50 K (v = 1m/s)

Surface temperature after 1 hour

Sliding friction o f po lyam ide 6 G andOilam id frictio n ring ST50 K (v= 1m/s)

M e a n c o e f f i c i e n t o f s l i d i n g f r i c t i o n

Surface pressure [MPa]

W e a r , [ µ m / k m ]

Bearing load [MPa ]

Surface pressure [MPa]

S u r f a c e t e m p e r a t u r e



Calaumid®/Calaumid®-Fe



C a l a u

m i d ®

Calaumid®

Calaum id 612 is a co-polyamide ba sed o n PA 6/12 G. Compa red to pure PA 6 G, shock an d impactresista nce a re highe r in Calaum id 612, mo istu re ab sorption is low er a nd creep resista nce isimproved. Because of the se m a terial properties Cala umid 612 is especia lly suita ble f or use in a reasw here increased shock load s are expected o r w here highe r fat igue resista nce and flexibility a re re-quired.

Typical applications are:

• Gear w heels• Too th ed racks• Pinions• Outrigg er f loat pad s

Ca laumid 1200 is the t rad e na me fo r PA 12 G, w hich is a lso ma nufa ctured from t he raw ma teria llaurin la cta m in a pressureless mono mer m oulding process. The sea mless tran sition from polyme-risa t ion to crysta l lisa t ion crea tes a high-crysta l line structure. This prod uces mat eria l propert iestha t a re fa r superior to extruded PA 12.

Advantages of Calaumid 1200 compared to other polyamides:

• Low w at er absorption compa red to ot her polyamides• This ma kes i t d imensiona lly sta ble a nd reduces the e f fects o f w a t er content on mechanica l

properties to a n ab solute minimum• Goo d creep resista nce, even a t high t emperatures• Go od shock and n ot ch impa ct resista nce, also a t t empera tures as low as –50° C• Go od resista nce to hyd rolysis a nd che micals in the pH 2-14 ran g e• Temp era tu re sta bility fro m –60 to + 110°C• Go od slip and a bra sion resista nce• Resista nt to stress cracking• Low specific we ight

The comb inat ion of t hese properties ma kes Calaumid 1200 a n idea l ma terial for g ea r comp one nts,especia lly if steel hubs are being mo ulded in during ma nuf a cture. These propert ies a re not com pletelyachieved by ot her the rmoplastics or bronze.

Dependence of the mechanical properties on the water content for Calaumid 1200

0 0,5 1,0 1,5 2,0Mass %

70

60

50

40

MP a

0 0,5 1,0 1,5 2,0Mass %

2800

2400

2200

1600

MP a

2000

1800

2600

-40 0 40 80 120ºC

2600

1800

1400

8

1000

600

2200MP a

Y i e l d s t r e s s

M o d u l u s o f e

l a s t i c i t y ( b e n d i n g )

M o d u l u

s o f e l a s t i c i t y

Wat er content

Tem pera tu re

Wat er cont ent



C a l a u

m i d ® - F e

Calaumid-Fe

Calau mid-Fe is mo ulded in a pressureless process in a fo rm-fit a nd n on -positive ma nne r arou nd a 2to 2.5mm dee p knurled stee l core. Combina tions w ith a luminium, sta inless steel and bra ss are alsopo ssible. The plastic can be eith er Cala umid 612 or Cala umid 1200.

The comb ina t ion o f the plast ic outs ide an d the meta l core i s especia l ly suita ble fo r opt imised

to rque t ransmission fo r compo nent p art s such as

• Spur w heels• Worm w heels• Bevel w heels• Sprocket w heels• Casto rs, guide ro llers a nd ro pe pulleys• Cam disks

The comb ina t ion o f a stee l core an d a p last ic cas ing uni tes the unique propert ies o f s tee l andplastic th at a re so h ighly valued in design . The shaf t-hub connection is calculated in the sam e w a ya s stee l , thus of f ering the possibil ity of a h igh de g ree of po w er tran smission. The a dvan ta ge s of

Calaumid-Fe:

• Mainta ins the time-tested met a llic sha ft -hub con nection• Runs q uietly• Weight a dvanta ge compa red to pure steel designs• Good noise a bsorption a nd vibrat ion b ehaviour• Good dry and emergency running properties• Optimum power transmission (calculated like steel)• Precise bea ring seat , hig h deg ree of fitt ing accura cy• High deg ree of t rue running

Calaumid

F

Fe-Kern

Ma t eria l: Ca la umid ® -FeV

Steel core: Ø 60mm x 38m mCalaum id disk: Ø 140mm x 38m mKnurl: Axia l a nd circumf erent ia l

knurl, DIN 82-RKE 2.0Ma t eria l st ee l: Ma ch in in g st ee l 9 SM n 28K

Max. axial load: 100 kN

F

Ma teria l: Ca la umid ® -FeV

Steel core: Ø 80mm x 20m mCalaumid disk: Ø 200mm x 33m mKnurl: Axia l a nd circumferent ia l

knurl, DIN 82-RKE 2.0Ma t eria l st ee l: Ma ch in in g st ee l 9 SMn 28K

Max. torque: 4,45 kNm

Axial load experiment Torque transmission test

Result of axial load: Result of torque transmission:



POM/PET



P O M

Polyacetal (POM)

Polyaceta l is a h igh crysta l l ine t hermo plastic w ith a h igh level of sta bi li ty and rig idi ty as we ll a sgo od s lid ing propert ies an d w ea r res ista nce w i th a low level o f moisture a bsorpt ion . It s goo ddimensiona l sta bi lity , except iona l f a t igue resis tance a nd excel lent ma chining propert ies makepolyacet a l a versati le desig n ma te ria l a lso fo r com plex compo nent s. POM sa tisf ies high surfa cefinish req uirement s.

Sta bi li ty, r ig id i ty a nd dimensiona l sta bi li ty can be fur ther improved b y ad ding g lass f ibres as afiller, alth ou g h th is de creases sliding prop erties.

A distinction is ma de be tw een ho mo polymers (POM-H) a nd copolymers (POM-C); ho mo polymersha ve a higher de nsity , hardness an d sta bi lity d ue t o their higher deg ree of crysta l linity . How ever,copolymers ha ve a h ighe r impa ct resista nce , grea t er ab ras ion res is tance an d b et t er therma l/chemical sta bility.

The po lyacet a l semi-f inished prod ucts tha t w e of f er – from w hich w e a lso ma nufa cture f inishedprodu cts– are pro duced from copolymers in an extrusion process.

Main properties

• High stability• Hig h rig idity• Hig h ha rdness• Good impact resista nce, a lso a t low temperat ures• Low level of moisture a bsorption (at sa tura tion 0.8%)• Goo d creep resistance• Hig h dimensiona l sta bility• Resista nt t o hyd rolysis (up to + 60° C)• Physiolog ica lly saf e

Colours:POM – C : na tura l/b la ckPOM – C + GF: black

Slip Sliding properties

POM-C has excel lent s lid ing propert ies and go od w ea r resista nce . Tog ethe r w i th i t s o th er out -stan ding propert ies, POM-C is w ell suited fo r sliding a pplications w ith me dium t o high load s. Thisa lso a pplies to a pplications w here high levels of h umidity or we tne ss are t o b e expected .

Because o f the c lose s ta t ic and dynamic coef f ic ients o f f r ic t ion , low s ta r t-up moments canbe implemented .

This do es not a pply to t he t ypes filled w ith g lass a s their sliding propert ies are m uch less th an th eunfilled types.

Weathering effects

POM-C is no t resista nt t o UV rays. UV rays, in comb inat ion w ith a tm ospheric oxyg en, o xidise thesurfa ce, and d iscolourat ion occurs or th e surfa ce becomes mat t . If t he ma teria l is subject t o t heeffects of UV rays for a long t ime, it tend s to b ecome britt le.

Chemical resistance

POM is resista nt t o w ea k acids, we ak a nd strong a lka l ine solutions, org a nic solvents and p etro l ,ben zole, oils and alcohols.

POM-C is not resista nt to stron g a cids (pH < 4) or oxidising ma te ria ls.



P O M

Behaviour in fire

POM-C is rated as no rmal flam ma ble. When the source of ignition is removed, POM-C cont inues toburn , fo rming drople ts . During the rmal decompo si t ion , f orma ldehyde can f orm. The o xygenindex (= the o xyge n concentrat ion required fo r comb ustion) at 15% is very low compa red to ot her

plastics.

Areas of use

• Gene ral ma chine eng ineering

• Vehicle construction• Precision mecha nics• Electrical industry• Informa tion technology

Applications• Spring elements• Bushes• Gear w heels• Sliding elements• Insulators• Pump component s• Casing part s• Va lves and valve bo dies• Counter pa rts• Precision p a rts

Machining

POM-C develops a frag ment ed chip a nd is thus idea l ly suited fo r machining on aut oma tic la t hes,but i t is a lso possible t o ma chine i t on cutt ing ma chine t oo ls. The semi-f inished prod ucts can bedri lled , mil led , saw ed, p laned an d t urned o n a l a the . I t i s a l so po ssible to cut threa ds or inser tthrea ded pa rts in t he m a terial. Genera lly no cooling or lubricat ing em ulsion is necessary.

To l imit ma teria l def orma tion due to internal residua l stress in semi-f inished products, the pa rts

should a lwa ys be m achined from the ge omet rical cent re of t he semi-f inished product , removingan even qua nti ty of mat eria l f rom a ll sides.

If ma ximum dimensiona l sta bi li ty is deman ded f rom t he f in ished compo nent s, the pa r ts to beman ufa ctured should be rough pre-machined and sto red for an in ter im period o r hea t t rea ted .The pa r ts can then be comple ted . More de ta iled in format ion o n in ter im s torage and hea t t rea t -ment , a s wel l a s o the r in fo rmat ion a bo ut ma chining , is prov ided in the chapter on “ Machiningg uidelines” .



P E T

Polyethyleneterephthalate (PET)

The mo lecule structure o f po lyethyleneterephtha la t e can be produced ei ther a s an amo rphous orsemi-crysta lline th ermo plastic. The a mo rpho us type is crysta l clea r w ith low er mecha nical sta bilitya nd inferior sliding properties.

The semi-crysta lline types, on t he o th er ha nd , have a high level of ha rdne ss, rig idity and stab ility

w ith excellent sl iding p roperties and low sl iding a bra sion. Because of i ts go od creep resistan ce,low level of m oisture a bsorption an d excellent d imensiona l sta bility, the ma te ria l is ide ally suite dfo r comp lex pa rts with t he high est dema nds on d imensiona l stab i li ty and surfa ce f inish. For thereasons men tioned a bo ve, only th e semi-crysta lline type is suitab le fo r sliding app lications.

The w ea r resista nce a nd sliding p ropert ies of PET-GL ha ve bee n improved compa red t o p ure PETby ad ding a special, homog eneo usly distribut ed solid lubricating a ge nt.

The po lye thy lene t erephtha la te semi-f in ished products tha t w e o f fer – and f rom w hich w e a lsoma nuf actu re all f inished prod ucts – a re ma nuf act ured f rom semi-crysta lline types in a n extrusionprocess.

Main properties

• High stability• Hig h rig idity• Hig h ha rdness• Low moisture ab sorption (at satura tion 0.5%)• Very go od creep resista nce• Very high d imensiona l sta bility• Consta ntly low sliding friction• Very litt le sliding a bra sion• Resista nt t o hyd rolysis (up to + 70° C)• Physiolog ica lly saf e

Colours

PET: na t ura l, b la ckPET-G L: lig h t g re y

Sliding properties

PETha s excellent sliding prope rties, very go od w ea r resistan ce and , in comb inat ion w ith its ot herprope rties, is an excellent ma te ria l for hig hly loa de d sl iding a pplicat ions. This a lso a pplies toa pplications w here high levels of humidity or w etn ess are expected.

The m od ified t ype PET-GL is especia lly suita ble f or hig hly loa de d sliding a pplicat ions in dryrunning operat ions due to its integ rated sol id lubricating a gen t. The sol id lubricating a gen t “ sel flubrica te s” th e PET-GL, w hich gives it excellent sliding pro pert ies a nd h ighe st w ea r resista nce w itha much high er load -bea ring streng th (pv limiting value) compa red t o p ure PET. It a lso p reventsth e stick-slip effe ct. The o th er prop ert ies a re eq ua l to t ho se of pure PET.

Weathering effects

PET is no t resista nt to UV rays. The ma te ria l surfa ce chang es w hen subjected to UV rays in com-bina tion w ith at mospheric oxygen. If t he ma terial is to be subjected to UV rays for long er period s,a b lack coloured t ype is recommend ed.



P E T

21

Chemical resistance

PETis resistant to w ea k acids an d a lkaline solutions, salt solutions, perchlorina ted an d fluorina tedhydro carbo ns, oi ls , fue ls, solvents an d surfa ce-a ctive substa nces. Stro ng pola r solvents ha ve anirreversible sw elling eff ect. PETis no t resista nt t o stron g a cids or alkaline solutions, este rs, ket on es

or chlorina ted hyd rocarbo ns.

Behaviour in fire

PETis rat ed as norma l flam ma ble. When t he source of ig nition is removed, PETcont inues to burn,forming droplets. The o xyge n index (the oxygen concentra t ion req uired fo r combustion) a t 23%is averag e compa red to ot her pla stics.

Areas of use Applications

• Gene ral machine eng ineering • Rat chet w heels• Vehicle construction • Bushes

• Precision mecha nics • Gear w heels• Electrical industry • Sliding element s• Informa tion t echnolog y • Insulators

• Ca sing part s• Counter component s• Precision bearings• Cam disks

Machining

PETdevelops a b rit t le , f low ing chip an d is suitab le for machining on a uto ma tic la the s, but i t cana lso b e ma chined on cutt ing ma chine t oo ls. The semi-f inished prod ucts ca n be dri lled, milled,saw ed, planed a nd t urned on a la t he. It is a lso po ssible to cut a thread into the ma teria l or insert a

threa ded element. G enera lly no cooling or lubrica ting emulsion is necessary.



Plastics that are highly resistant

to chemicals



Polyethylene is a semi-crysta lline the rmopla stic w ith high t oug hness a nd chem ical resistan ce, rat herlow mechanical strengt h in compa rison t o o ther plast ics and canno t b e used a t high temperat ures.The individua l po lye thy lenes d i f fer in reg ard to the i r molar ma ss (molecula r w eight ), w hich i simporta nt f or the respect ive physica l prope rt ies . This mea ns tha t in ad di t ion t o t he commo nprope rties th a t a ll type s ha ve, certa in ones have type -specific prop erties.

The po lyeth ylene semi-finished prod ucts that w e o ffer – from w hich w e a lso m an ufa cture finishedprod ucts – consist of hig h den sity polyeth ylene types produced b y extrusion o r moulding pro ces-ses.

Main properties

• Low de nsity comp a red t o o th er ma te rials (0.94 g /cm3)• Hig h impa ct resista nce, also a t low tem perat ures• Minimum w a te r ab sorption (< 0.01%)• Excellent chemical resistance• Hig h corrosion resista nce

• Anti-adhesive• Very go od e lectrical insulat or• Hig h vibra tion a bsorption• Physiolog ically saf e (does no t app ly to regen erat e semi-finished prod ucts)

Colours

PE – HD: na tura l, b la ckP E – HMW: na tura l, g re e nPE – UHMW: na tura l, green , black

Other colours on req uest.

Sliding properties

PE-HD (PE 300; mo lar m a ss a ppro x. 200,000 g/mo l) is very suita ble fo r w elding du e t o its relat ivelylow mola r mass; how ever, it is not a bra sion resistan t a nd h as low sta bi li ty va lues. This lead s to ahigh level of sliding a bra sion , w hich excludes its use in sliding a pplica tion s.

PE-HMW (PE 500; mola r ma ss a ppro x. 500,000 g /mo l) ha s b et t er sliding pro pert ies beca use o f itshigher mo lar mass an d is a lso more a bra sion resistant tha n PE-HD. In comb ination w ith i ts g oo dto ug hness, it is suita ble for use in low stress componen ts tha t a re not subject t o a ny high deg reeof sliding a bra sion.

PE-UHMW (PE 1000; mo lar m a ss appro x. 4,500,000 g/mo l). Beca use o f its hig h m ola r ma ss it ha svery goo d w ear resista nce , bend ing st reng th a nd impact resista nce and g ood noise ab sorbt ion .Due t o i ts excellent sliding properties and low sliding ab rasion, i t is the idea l mat eria l fo r lightlyloa ded component s.

Both PE-HMW und PE-UHMW are a lso ava i lable a s reg enera t ed ma ter ia l , a l thoug h i t m ust benot ed tha t t he respective physical properties are slight ly reduced.

Chemical resistance

All PE types a re resistan t to acids, a lkal ine solution s, sa l ts and sa l t solutions, a lcoho ls, oi ls, fa ts ,

w axes and ma ny solvent s. Aroma tics and h alog ena ted hydrocarbo ns cause swe lling. All PE typesare not resista nt to st rong ox idising ma ter ia ls (e .g . n it r ic ac id , chromic ac id or ha logens), a ndthe re is a da ng er of stress corrosion cracking .

Polyethylene (PE)

P E



P E

Weathering effects

As a g enera l rule, no PE types a re resista nt to UV rays. This do es not a pply to t he b lack colouredtypes, w hich a re resista nt to UV rays (a lso in comb ination w ith a tmo spheric oxyge n).

Behaviour in fire

All PE types are rat ed a s norma l flam ma ble. When t he source of ignition is removed t hey continueto burn and form drops . How ever, apa r t f rom carbon d iox ide , ca rbon mo noxide a nd w a t er, onlysmal l q uan t i t ies o f ca rbon black and m olecula r const i tuents o f the plast ic develop as conf lag -rat ion g ases. The o xyge n index (the oxygen concentra tion req uired fo r combustion) at 18% is low compa red to o the r pla stics.


PE-HD PE-HD

• Electroplat ing industry • Comp one nt part s in chemical plant construction• Chemical ind ustry • Fittings• Chemical appa rat us construction • Inserts

• Sta cking b oxes

PE-HMW PE-HMW• Foo d industry • Cutt ing ta ble surfaces• Mea t processing industry • Agita t or blad es• Sporting venue construction • Wa ll lining s in ref rig era tion ro om s

• Impact ba nds• Knife blocks

PE-UHMW PE-UHMW• Electroplat ing industry • Rop e pu lleys, guide rollers• Genera l ma chine eng ineering • Sprocket w heels an d pinions• Coa l processing • Gear w heels• Packag ing industry • Cha in g uides• Conveying technology • Slides• Paper industry • Suction plate s• Electrical industry • Knife -over ro ll coa te rs

• Chute lining s for silos• Conveyor tro ugh linings• Abra sion p rotection strips

Machining

In ad di t ion t o th e go od w elding propert ies o fPE-HD and PE-HMW, all PE types can also bema chined o n ma chine to ols. The semi-finishedproducts can b e d ril led, mil led, saw ed, plane dan d t urned on a lat he. It is also po ssible to cut athread in to the ma ter ia l or inser t a t hreadedelement. As a rule, no cooling or lubricatingemulsion is necessary.



P P

Polypropylene is a semi-crysta lline th ermo plastic wit h high rig idity an d very go od chemical resi-stance. Chara cteristic for polypropylene is a CH3 side-gro up in t he mon ome r structura l unit, w hichcan b e aligne d in va riou s spat ial positions during polymerisa tion . The various spa tia l a lig nme nt sare sign ificant f or the physical properties an d differ according to the f ollow ing:

• Isota ctic (regular, one-sided alignmen t in the ma cromo lecule)• Syndiota ctic (regular, doub le-sided alignmen t in the ma cromo lecule)• Ata ctic (irregular, ran do m a lig nment in the ma cromo lecule)

Alignment

A dist inction is a lso ma de b etw een ho mopo lymers and copo lymers; copo lymers a re toug her butha ve less mecha nical and chemical sta bility.

As the ph ysical propert ies improve considera bly w ith th e increa se in t he isot a ctic concent rat ion inthe polymer, isotactic polypropylene homopolymers should be the f irst choice for use in thetechnica l a rea . The po lypropylene semi-f in ished products tha t w e o f fer – f rom w hich w e a lso

ma nufa cture finished prod ucts – a re produced by extrusion or mo ulding processes.

Main properties

• Low de nsity comp a red t o o th er ma te rials (0,91 g /cm3)• Minimum w a te r ab sorption (< 0.01%)• Excellent chem ica l resista nce, a lso t o solvent s• Hig h corrosion resista nce• Relatively high surfa ce ha rdness• Very go od e lectrical insulat or• Physiolog ica lly safe

Colours

Nat ural (w hite), g rey (≈ RAL 7032)Other colours ava ilab le on reque st.

Slip properties

PP-H is subject to strong sliding ab rasion an d is thu s not suita ble f or use in sliding ap plications.

Chemical resistance

PP-H is resista nt to a cids, alkaline solutions, sa lts and salt solutions, a lcoh ols, oils, fa ts, w a xes a ndma ny solvents. Aroma tics and ha logen at ed hydrocarbo ns cause sw elling. PP-H is not resista nt tostrong oxidising ma terials (e.g. n itric acid, chromic acid o r ha logen s) a nd the re is a da ng er of stresscorrosion cracking .

Behaviour in fire

PP-H is ra te d a s no rma l f la mma ble. When t he source of ig nit ion is remo ved PP-H con tinues toburn , forming drople ts. How ever, apa r t f rom carbon dioxide , ca rbon m ono xide a nd w a t er, onlysma l l q uan t i t ies o f ca rbon black and m olecula r const i tuents o f t he plas t ic develop as conf lag -ration g ases.

The o xyge n index (the oxygen concent rat ion req uired fo r comb ustion) at 18% is low compa red t oother plastics.

Polypropylene (PP)



P P

Weathering effects

PP-H is no t resista nt to UV rays. UV rays, in comb inat ion w ith a tm ospheric oxyge n, oxidise th esurfa ce and d iscolourat ion occurs. If th e ma te rial is exposed to th e eff ects of UV rays for a long erperiod, this w ill cause irreparab le da ma ge a nd d ecomposition o f the surface.


• Electroplat ing industry • Pump parts• Chemical ind ustry • Compone nt pa rts in chemical appa rat us construction• Machine eng ineering • Fittings• Sta mping /punching plant s • Va lve bo dies

• Product h olders for electroplating processes• Punching pad s

Machining

In a dd ition t o its go od w elding prope rties, PP-H can a lso b e ma chined on ma chine t oo ls. The semi-finished produ cts can be drilled, milled, saw ed, plane d a nd t urned o n a lat he. It is a lso po ssible tocut a thread in to the mat er ia l or inser t a thread ed e lement . Ge nera l ly no cool ing or lubr ica t ingem ulsio n is ne cessa ry.

During cut t ing , i t is very importa nt t o ensure tha t t he to o ls tha t a re used a re a lwa ys ad equa te lysharp . Blunt t oo ls cause the surfa ce to hea t , w hich can cause “ smearing ” an d conseq uent lyuna ccepta ble surface f inishes.



P V C

Polyvinylchloride (PVC)

Polyvinylchloride – ha rd (PVC-U) is a n a mo rpho us therm op lastic wit h no a dd ed p lasticiser. It h a s ahigh ha rdne ss an d rigidi ty . Accord ing t o DIN 16 927 the m a te ria l is classi f ied a s norma l sho ckresista nt , ho w ever it s toug hness va lues bo rder on be ing ra t ed as h ighly shock resis tant , w hichg ives it a h igh d eg ree o f sa f e ty in rega rd to the design o f compo nent s. The po lyv iny lchlor idesemi-f in ished products tha t w e o f fer – f rom w hich w e a lso m anuf acture f in ished products – a re

prod uced in extrusion or mo ulding pro cesses.

Main properties

• Hard surface• High rigidity• Low w at er ab sorption• Excellent chemical resistance• Fire re sist a nt (UL 94 V 0)• Easily thermof ormed• Can be b onded• Goo d cutt ing properties

Colours

grey (≈ RAL 7011), bla ck, red, t ra nspa ren t

Other colours ava ilab le on reque st.

Sliding properties

PVC-U is no t subject t o a ny ma jor sliding a bra sion a nd is th us suita ble fo r use in sliding a ppli-cations.

Weathering effects

PVC-U is not resista nt to the e f fects o f UV rays. In comb ina t ion w i th a tmo spheric oxyge n, th esurface oxidises and d iscoloura tion o ccurs. If t he ma te ria l is exposed t o UV rays and a tm osphericoxygen fo r long er period s, irrepara ble da ma ge a nd d ecomposition o f the surface w ill occur.

Food law suitability

PVC-U do es not comply w ith t he req uirement s of th e Ge rma n Fed era l Insti tut e fo r Risk Assess-ment (BgVV) or the FDA an d ma y not b e used for ma nufa cturing consumer go ods tha t come intodirect cont act w ith food.

Chemical resistance

PVC-U is resista nt to a cids, a lkal ine solutions, a lcoho ls, oi ls, fa ts , a l ipha tic hydroca rbo ns an dpetrol.PVC-U is not resista nt to ben zole, chlorinat ed hydrocarbo ns, keto nes or e sters.In comb inat ion w ith strong oxidising ma terials (e.g . nitric acid o r chrom ic a cid), there is a d an g erof stress corrosion cracking .

Behaviour in fire

PVC is ra t ed as f ire resista nt in the h ighest ca t eg ory, even w ithout ad dit ives. When t he source ofignit ion is remo ved, PVC is self-exting uishing .The oxygen index (the oxygen concentra t ion req uired fo r combustion) a t 40% is very high com -pa red w ith oth er plastics.



P V C


• Electroplat ing industry • Pump parts• Machine engineering • Fittings• Filling plan ts • Va lve bo dies

• Photo industry • Compone nt pa rts in chemica l plan t construction• Feed t ab les• Machine and eq uipment covering

Machining

In a dd it ion to i ts go od w elding properties an d t he po ssibi li ty of b ond ed connections, PVC-U cana lso b e ma chined o n ma chine t oo ls. The semi-f inished prod ucts ca n be dri lled, milled, saw ed ,planed a nd t urned on a la t he . It i s a l so po ssible to cut a t hread in to the m at er ia l or insert athrea ded element . Genera lly no cooling or lubricating emulsion is necessa ry.

During processing it is very importan t t o e nsure tha t t he t ools that are used a re a lw ays adeq uat elysharp. If this is not the case, the high t empera tures ca used b y the blunt cutting e dg e can cause the

ma teria l to decomp ose and , in combinat ion w ith a t mospheric moisture, can cause sma ll q ua nti-ties of h ydrochloric acid to fo rm a s aerosols.

In ad dition, because of its ha rd-brittle properties, we recomme nd t ha t elastom er or thermoplasticw ashers a re used fo r PVC-U compo nent par t s tha t a re t o b e f a sten ed b y screw ing . The use o fw ashers such a s this reduces the d an g er of t ransmitting high stresses by tigh ten ing th e screw s an dthe stress cracking aro und t he ed ge o f th e drilled hole tha t t his causes.



P V D F

Polyvinylidenefluoride (PVDF)

Polyv iny liden ef luor ide is a h igh crysta l line thermo plast ic w i th g oo d mechanica l , thermal a ndelectrica l propert ies. As a fluoro plastic, po lyvinylidene fluoride ha s excellent chemical resistan cew i thout t he d isad vanta ge s o f low mechanica l va lues an d di f f icult w orkabi lity o f o t her f luoro-plastics. Our polyvinyliden e semi-finished pro ducts – from w hich w e a lso ma nufa cture a ll f inishedproducts – are ma nufa ctured in extrusion or mo ulding processes.

Main properties

• Low den sity in compa rison t o ot her • Hig h chem ica l resista ncefluoroplastics • Goo d h ydrolytic sta bility

• Goo d mecha nical sta bility compa red to • Wea the r resistantot her fluoroplastics • Rad iation resista nt

• Can b e used cont inuously at high t empera tures • Goo d e lectric insulato r(+ 140° C in a ir) • Fire re sist a nt (UL 94 V 0)

• Absorbs practically no w at er • Physiolog ica lly safe• Go od d imensional sta bility • High ab rasion resista nce

Colours

na tura l (w hite to ivory)

Sliding properties

PVDF ha s g oo d sliding prop erties, is resista nt t o w ea r an d is very suita ble fo r chem ica lly stressedsliding app lications th a t are also subjected to the rmal influences. How ever, in constructive design ,the relat ively high coeff icient of the rmal expansion should b e considered .

Resistance to radiation / Weathering effects

PVDF is resista nt to bo th b-rays an d g-rays as w ell a s UV rays in conn ection w ith a tm osphericoxygen. Hence PVDF is ideal for use in the pharmaceutical and nuclear industries and underw eat hering ef fects.

Chemical resistance

PVDF is resistan t t o a cids an d a lka l ine solutions, sa l ts a nd sa l t solution s, a l ipha tic and a roma tichydro carbo ns, alcoh ols an d a roma tics. PVDF is no t resistan t t o ket on es, amines, fum ing sulphuricacid , n i t r ic ac id or to severa l ho t a lka l i s (concentra t ion re la ted) . Dimethy l formamide anddimet hyl a ceta mide dissolve PVDF..

Behaviour in fire

Even w ithout a dd itives, PVDF is rat ed in t he hig hest cat eg ory a s fire resista nt . When t he source ofignition is remo ved, PVDF extinguishes itself . At 78%, the oxygen index (= th e concent rat ion o foxygen required fo r combustion) is very high compa red t o ot her plastics.


• Chemical a nd petro chemical industries • Pump parts• Pharma ceutical indu stry • Fit t ings a nd f i t t ing component s• Text ile ind ust ry • Valves an d va lve compo nent s• Paper industry • Seals• Foo d industry • Friction bearings

• Comp one nt pa rts in plant /ap para tusengineering

Machining

In a dd ition t o its go od w elding suita bility, PVDF can a lso b e ma chined on m achine to ols. With th erespective surface treatment, PVDF can be bonded with a specia l solvent adhesive. Fluoropolymers decompose a t tempera tures abo ve approx . 360 °C and form highly a gg ressive and tox ichydrof luor ic ac id . As polymer dust can f orm w hen t he ma ter ia l is be ing ma chined, smokingshould not b e permitted a t the w orkplace.



P T F E

Polytet raf luoroet hylene is a h igh crystalline t hermo plastic w ith excellent sliding prop erties, a nt i-a dh esive surfa ces, excellent insulat ion prop erties, an a lmost universa l chemical resista nce a nd a nexceptiona lly broa d t empera ture de ployment spectrum. How ever, this is off set by low mechan ica ls t rength an d a h igh specif ic w eight compared to o t her p las t ics. To improve the mechanica lproperties, polytet rafluoroe thylene is compoun ded w ith fillers such as glass fibre, coa l or bronze .

The polytet raf luoroet hylene semi-finished prod ucts th at w e off er – from w hich w e also ma nufa c-tu re all f inished pa rts – a re prod uced in pressure sint ering a nd ram extrusion processes, f ilms a reprodu ced in a peel process.

Main properties

• Excellent sliding prop erties• Hig hest che mical resista nce, a lso t o solvent s (limited w ith PTFE + bro nze )• Resista nt to hyd rolysis (limite d w ith PTFE + bro nze )• Hig h corrosion resista nce (limite d w ith PTFE + bro nze )• Broad tem perat ure deployment spectrum (-200°C to + 260°C)• Resista nt to w eat hering• Does not ab sorb m oisture

• Physiolog ica lly safe (no t PTFE + coa l /+ bro nze )• Go od electrica l insulat or (not PTFE + coa l /+ bro nze )• Goo d t herma l insulat or (not PTFE + coal /+ bron ze)• Anti-adhesive• Virtua lly unw ett ab le w ith liquids• Fire resist a nt

Colours

PTFE pure : w eißP TFE + g la ss: lig h t g re yPTFE + co al: b la ckPTFE + bron ze: brow n

Sliding properties

PTFE ha s excellent sliding p ropert ies a nd be cause of i ts very close sta t ic and dyna mic abra sionvalues, i t prevents t he “ st ick-sl ip ef fect” . How ever, due to i ts low mechan ical streng th, PTFE ha shigh sliding a bra sion a nd a ten den cy to creep (cold flow ). Hence, unfilled PTFE is only suitab le fo rs lid ing appl ica t ions w i th low mechanica l loa d . I t s loa d bea r ing capa city can be construct ive lyimproved b y eq uipping th e s lid ing e lement w i th severa l cha mbers . It m ust b e ensured tha t t hechamb er is fully enclosed so tha t t he slip lining ca nno t escape (“ flow out ” ).

PTFE + g lass ha s w orse slip prope rties tha n pure PTFE du e t o t he f iller, but it can b ea r much hig herload s. Sl iding a brasion a nd t he coeff icient o f elong at ion are reduced, w hile creep resista nce anddimensiona l sta bility increase. The g lass pa rticles emb edd ed in th e ma terial cause high er w ea r onthe ma ting part tha n pure PTFE.

PTFE + coa l has similarly go od slip prope rties as pure PTFE, but be cause o f t he a dd ition o f a filler, itha s much be tt er mecha nical sta bility. As w ith g lass a s a f iller, sliding a bra sion a nd t he coef ficientof elong a tion a re reduced w hile creep resista nce an d d imensional stab i li ty increase. Sl iding ele-ments f i lled w ith coal can be used for a pplicat ions tha t a re occasiona lly or constan tly surround edby w a ter.

PTFE + bro nze ha s the be st me chan ica l va lues of a ll filled PTFE type s and is very suita ble f or slidinga pplica tion s. The f iller ca uses th e low est sliding a bra sion of a ll PTFE type s. In a dd ition t o t his, th er-ma l cond uct iv ity, an d conseq uent ly the d issipa t ion o f f r ic t ion hea t f rom the f r ic t ion bea r ing , i sconsidera bly improved compa red to ot her sliding m at erials, w hich leads to a longe r life.

Polytetrafluoroethylene (PTFE)



P T F E

Weathering effects

All PTFE type s are very resistan t to UV rays, even in comb inat ion w ith a tm ospheric oxygen. Nooxida tion or discoloura tion ha s bee n ob served.

Chemical resistanceUnfilled PTFE is resistan t t o a lmost a ll med ia a pa rt fro m elemen ta l f luorine, chlorot rifluoride a ndmo lten o r dissolved a lkali meta ls. Ha loge na te d hyd rocarb on s cause minor, reversible swe lling. Inthe case of f illed PTFE, due to the filler one can reckon w ith a low er chemical resista nce, altho ug hit is the filler that fo rms the reaction pa rtner t o t he me dium, not the PTFE.

As a rule, it can b e said t ha t t he t ypes filled w ith coa l are no t mu ch less resista nt t ha n pure PTFE.The t ypes f il led w ith g lass are resista nt to acids and oxidising a ge nts but less resista nt to a lkal is .The t ypes filled w ith b ronz e ha ve a m uch low er chemical resista nce th a n pure PTFE.

Befo re using filled PTFE type s in chemically burde ned environme nt s, their resista nce to th e respec-tive med ium should a lw ays be t ested.

Behaviour in fire

PTFE is ra t ed a s f ire resista nt in the highest ca t eg ory. It do es not burn w hen a n ignit ion source isad ded . The o xyge n index (the oxygen con centra t ion required fo r comb ustion), a t 95% is one ofthe high est compa red to o the r plastics.


• Chemical ind ustry • Friction bearings• Machine engineering • Bearing bushes• Precision mecha nics • Sha ft seals• Electrical industry • Piston ring s• Text ile ind ust ry • Va lve sea ts/sea t ring s• Paper industry • Insulators• Foo d industry • Flat seals• Aerospa ce ind ustry • O ring s• Building a nd b ridg e construction • Test ja cks

• Threa d g uides• Anti-adhesive liners

Machining

PTFE is di f f icult to w eld a nd tha t o nly by using a specia l process. It can b e ma chined on ma chineto ols. The semi-finished prod ucts ca n be drilled, milled, sa w ed , plan ed a nd t urned o n a lath e. It isa lso po ssible to cut a threa d in to the ma ter ia l or inser t a threa ded e lement . PTFE canalso b e bo nded w hen t he surfa ce has been suita bly treat ed b y etching w ith specia l etching f luid.

Up to a pprox. 19°C, PTFE is subject t o a pha se tran sit ion w hich is no rma lly accompa nied b y anincrease in volume o f up to 1 .2%. This mea ns tha t f inished part s tha t are dimensiona lly stab le a t23° C can ha ve considerable d imensiona l de v ia t ions a t tempe ra t ures be low 19° C. This must beconside red in the d esig n a nd d imension ing o f PTFE compo nen ts. When t he ma te ria l is be ingmachined, a t tent ion must be pa id tha t g ood hea t d issipa t ion i s gua ranteed for par ts wi th mini-mum t olerances, othe rw ise the g oo d insula t ion properties can lead t o d imensional devia t ions infinished part s af ter cooling b ecause of the h ea t build-up an d th erma l expansion.

Fluoropolymers decompo se a bo ve appro x. 360° C forming h ighly ag gressive a nd to xic hydrofluoricacid . As polymer dust can fo rm w hen t he ma ter ia l is be ing ma chined, smoking should no t b epermitted a t t he w orkplace.



High performance plastics



Polyethe rethe rketon e is a semi-crysta l line th ermop lastic w ith excellent sl iding propert ies, veryg oo d mecha nica l propert ies, even und er therma l load a nd a n excellent resista nce to chemica ls.The high continuous w orking tem perat ure rounds out the profile of this high -performa nce pla stica nd ma kes i t a v irtua l ly universal ly useab le design ma te ria l for hig hly stressed pa rts. Thepolye there t herketo ne semi-f in ished prod ucts tha t w e o f f er – f rom w hich w e a lso ma nufa cture

finished pa rts – a re prod uced in extrusion o r moulding processes.

Main properties

• High continuous w orking temperat ure • Hig h dimensiona l stab ility(+ 250° C in a ir) • Excellent chemical resista nce

• Hig h mechan ica l streng th • Resista nt t o hyd rolysis• Hig h rig idity • Go od electrical insulato r• Hig h creep resistance, also a t high t empera tures • Rad iation resista nt• Go od sliding properties • Physiolog ica lly safe• Hig h w ea r resista nce • Fire re sist a nt (UL 94 V 0)

Colour

nat ural (≈ RAL 7032), b la ck

Sliding properties

PEEK idea l ly combines go od sl iding properties w ith high mechanical streng th an d therma l sta bi-lity a s we ll a s excellent chemical resista nce. Becau se of t his, it is suita ble f or sliding a pplicat ions.Mod if ied types cont a ining carbo n f ibre, PTFE an d g raphite – w ith highest w ea r resista nce, a low coef f icient o f f r ic t ion a nd a h igh pv limit ing va lue – a re ava i lab le fo r compo nent par ts tha t a resubject to e specially high ab rasion a nd w ea r.

Resistance to weathering

PEEK is resista nt to X rays, b-rays and g-rays. Hence PEEK is idea l for use in th e ph a rma ceutical a nd

nuclea r industries. PEEK is not resista nt to UV rays in comb ination w ith a tmo spheric oxygen .

Chemical resistance

PEEK is resista nt to no n-oxidising a cids, con cent rat ed a lka line solut ions, sa lt solut ions, clea ningag ent s or para f f in oi ls. It is not resista nt to oxidising a ge nts such a s concent ra t ed sulphuric acid,nitric acid o r hydrog en f luoride.

Behaviour in fire

PEEK is rat ed f ire resista nt in t he h ighe st cat eg ory. When th e source of ig nition is remo ved PEEK isself-exting uishing . The o xygen ind ex (th e oxyg en con centra tion req uired fo r com bustio n) is 35%.

Areas of use Applications• Chemical an d petro chemical industries • Gear w heels• Pharma ceutical industry • Friction bearings• Food industry • Bobbins• Nuclea r indu stry • Fittings (e.g. casing fo r hot w at er meters)• Aerospa ce ind ustry • Valves• Defence technolog y • Pisto n ring

• Parts for car eng ines (e.g. b ea ring ca g es)Machining

In a dd it ion t o i ts go od w elding a nd b ond ing propert ies PEEK ca n be ea sily ma chined . The semi-f inished prod ucts can be d ril led, mil led, saw ed, plan ed a nd t urned o n a la th e. It is a lso po ssibleto cut a thread into the m at eria l or insert a thread ed element. General ly no cooling or lubricatingem ulsion is ne cessa ry.

Polyetheretherketone (PEEK)

P E E K



P S U

Polysulphone is an am orphous the rmoplas t ic w i th h igh m echanica l s tab i li ty and r ig id i ty an dremarkably high creep resista nce across a w ide t emperat ure rang e a nd h igh continuous wo rkingtem pera t ure for a n a morpho us plas t ic. In a dd i t ion , po lysulphone is t ran sparent b ecause o f i t sam orphous mo lecule structure. Its very g oo d resista nce to hydrolysis and very g oo d dimensiona lsta bi l ity roun d o ut t he prof i le . The po lysulphon e semi-f inished prod ucts tha t w e of f er – from

w hich w e also manuf acture finished p art s – a re produced by extrusion.

Main properties

• Hig h continuo us wo rking te mpera ture (+ 160°C in a ir)• Very go od resista nce to hydrolysis (suitab le for repeat ed stea m sterilisa tion)• High toug hness, a lso a t low temperat ures• Hig h dimensiona l sta bility• Goo d electrical insulato r• Hig h mechan ical sta bility• Hig h rig idity• Hig h creep resista nce across a w ide tempe rat ure rang e• Good resista nce to radia t ion

• Physiolog ica lly saf e• Fire re sist a nt (UL 94 V 0)

Colour

Nat ural (hon ey yellow , tra nslucent)

Sliding properties

PSU is subject t o stron g sliding ab rasion a nd is thus unsuitab le for sliding app lications.

Resistance to radiation/weathering effects

PSU is resista nt to X ra ys, b-rays, g-rays an d m icrow a ves. Hence PSU is idea lly suited fo r use in t he

pha rmaceut ica l, fo od an d nuclear industries.

Chemical resistance

PSU is resistan t t o inorg a nic a cids, alka line solutions and salt solution s, as w ell as clea ning a g ent sa nd pa raf f in oi ls . It is no t resistan t t o keto nes, esters, chlorinat ed hyd rocarbo ns or aroma tic hy-drocarbons.

Behaviour in fire

PSU is ra te d a s fire resista nt in the h ighest ca teg ory. When t he source of ignition is remo ved, PSUis self-exting uishing . The o xyg en ind ex (th e o xyg en con centra t ion req uired fo r combu stion) is30%.


• Electro-technology • Bobbins• Electronics • Inspection g lasses• Vehicle constructio n • Sea ling ring s• Equipment engineering • Eq uipment casing• Aerospace industry • Insulat ing sleeves

Machining

In a dd i t ion t o i t s go od w elding and bo nding propert ies PSU can b e ea si ly machined. The semi-f inished prod ucts can be d ril led, mil led, saw ed, plan ed a nd t urned o n a la th e. It is a lso po ssibleto cut a thread into the mat eria l or insert a thread ed element. General ly no cooling or lubricatingem ulsio n is ne cessa ry.

Polysulphone (PSU)



P E I

Polyetherimide is an a morphous the rmoplastic with high me chanical stab il ity a nd rigidi ty as w ellas remarkably h igh creep res is tance across a wide tempera ture range and h igh cont inuousworking tempera ture for an amorphous plas t ic . In addi t ion , po lye ther imide i s t ransparentbeca use of its amo rphous molecule structure. Its very go od resista nce to hydrolysis an d very go oddimensiona l sta bility round out the pro file.

The polyethe rimide semi-finished pro ducts tha t w e of fer – from w hich w e also man ufa cture finishedpa rts – are pro duced b y extrusion.

Main properties

• Hig h continuous w orking tem perat ure (+ 170°C in a ir)• Hig h mechan ica l sta bility• High rigidity• Hig h creep resista nce across a b roa d te mpera ture rang e• Hig h dimensiona l stab ility• Very go od resista nce to hydrolysis (suitab le for repeat ed steam sterilisat ion)

• Go od electrica l insula to r• Goo d resista nce to rad ia t ion• Physiolog ica lly safe• Fire re sist a nt (UL 94 V 0)

Colour

Nat ural (am ber, translucent )

Sliding properties

PEI is subject to stro ng sliding a bra sion a nd is th us unsuita ble fo r sliding a pplica tion s.

Resistance to radiation/weathering effects

PEI is resista nt t o x-ra ys, b-rays and g-rays as w ell a s UV-rays in comb inat ion w ith a tm osphericoxygen. Hence PEI is ideally suited fo r use in th e pha rmaceut ica l and nuclea r industries and unde rw eat hering ef fects.

Chemical resistance

PEI‘s resista nce shou ld be t ested b efo re it is used w ith keto nes, aroma tic hydroca rbon s or ha lo-g ena ted hydrocarbo ns. Alkaline reag ent s with pH values > 9 should b e completely avoided.

Behaviour in fire

PEI is rat ed a s fire resista nt in th e highe st cat eg ory, also w ithout ad ditives. When t he source of ig-nition is remo ved, PEI is self-exting uishing . The o xygen ind ex (th e oxyg en con cent rat ion req uiredfo r combustion), a t 47% is very hig h compa red t o o the r plastics.


• Electro-technology • Bobbins• Electronics • Inspection g lasses

• Vehicle construction • Eq uipment casing• Equipment engineering • Insulat ing sleeves

Polyetherimide (PEI)



Structure and properties

of plastics

(CH2)5

HN – CO – – – –

–– [NH – (CH2)6 – NH – (CO – CH2)4 – CO ]n ––2

– [NH – (CH2)11 – CO]n ––



S t r u c

t u r e a n d p r o p e r t i e s

1. Fundamentals

In g enera l te rms, p last ics a re ma cromo lecula r compo unds ma nufa ctured f rom exist ing na tura lsubsta nces by chemical con version or by synt hesising pro duct s from t he chemical decomp ositionof coa l , pe tro leum o r na tura l g as . The ra w ma ter ia l p las t ic fusions produced by conversion orsynt hesis are usually fo rmed int o semi-finished prod ucts or finished prod ucts by app lying t empe -rat ure a nd pressure. These processes include , am ong ot hers, injection mou lding a nd extrusion.Except ions to t his a re the polyamide semi-finished prod ucts manuf a ctured b y Licha rz in sta tic andcentrifuga l mou lding processes, a s the se metho ds w ork w ithout pressure.

2. Structure

2.1 Classification

Usually plastics a re classified in tw o ma in grou ps – th ermo plastics a nd d uropla stics.

• Whe n the y a re he a te d to a n a d e q ua te de g re e , thermoplastics sof t en unti l they are melted a ndthe n ha rden a ga in on coo ling . Forming a nd refo rming t hermoplastics is ba sed o n this repeat a-ble process. P rov ided the hea t ing do es not cause excess therma l st ress leading to chemica ldecomp osition, the re is no chan ge t o th e ma cromo lecules.

• Because of t heir molecula r structu re, duroplastics ca nno t be re f o rme d a f t e r the y ha v e be e noriginally fo rmed, not even at h igh tem perat ures. The original forma tion is ba sed o n a chemicalreaction of intermediates – most of which are not macromolecular – to closely cross-l inked

macromolecules.

In DIN 7724, plast ics a re cla ssi f ied a ccord ing t o t heir beha viour w hen subjected to di f fe renttem perat ures. This leads t o the fo llow ing classification:

• Plastomers (= th ermo plastics) a re no n-cross-linked plastics th a t rea ct en erg y-elastically (met a l-elast ica l ly) w ithin the ir service tem perat ure rang e, and w hich sof ten a nd me lt f rom a ma teria l-specific tem perat ure onw ard s.

• Thermoplastic elastomers a re p hysically or che mically coa rse-meshe d, cross-linked plastics orplast ic mixtures. In their normal service temperature range they behave entropy-elast ica l ly(rubber-elastically) but at high t emperat ures they softe n to the po int of m elting .

• Elastomers a re coa rse-g rained , temp era ture-sta ble, cross-l inked plast ics w hich a re ent ropy-elastic (rubb er-elastic) in t heir service te mpera ture rang e. They ca n b e f ormed reversibly a nd donot f low unti l they reach their decomposit ion temperat ure rang e.

• Duromers (= du rop lastics) a re close-me shed , cross-linked pla stics, w hich rea ct ene rg y-ela stically(met a l-e las t ica l ly ) in t he i r service t empera t ure rang e a nd w hich d o n ot f low unt i l they reachtheir decomposit ion tempera ture rang e.

2.2 Structure and form of the macromolecules

Apa r t f ro m a f e w e xce pt io ns, the p la s t ics tha t a re p ro duce d to da y a re g e ne ra lly ba se d o n t heab ility o f ca rbon to form long cha ins through a t omic bond s. As opposed t o ion bo nds , the o utershell of t he carbon a to m f i lls to the no ble-ga s configurat ion w ith eight electrons. Bond pa rtnerscan be comple te a to m g roups or sing le a to ms such as hydrogen, o xyge n, n it rog en, sulphur orcarbon.

Structure and propertiesof plastics



S t r u c


Throu g h synt hesis ma ny ind ividua l small molecules (= monomers) o f o ne or mo re sta r t ing pro-ducts are bo nded to g ethe r chemical ly into ma cromo lecules (= polyme rs). As a rule, th e resultingcha ins a re be tw e e n 1 0-6 a nd 10-3 mm lon g . The size of t he m a crom olecules is expressed b y thedeg ree o f po lymerisa t ion n or by t he mo lecular w eight . As i t is not possible to a chieve a ho mo-g eneo us distribution o f th e chain leng th in polymerisat ion, th e values a re given a s a verag es. In

techno logy, it is usual to stat e a mea sure f or t he viscosity (e.g. m elt index, M.F.I.) instea d of the de-g ree of polymerisa tion o r the mo lecular w eight . The high er n is, th e h ighe r th e viscosity.

In th e fo rmat ion o f ma cromo lecules a d is t inct ion i s ma de b etw een l inea r, branched a nd cross-linked mo lecule structure s.

Linear or branched macromolecules produce thermoplastics, weak cross-l inked ones produceelastomers and strongly cross-linked macromolecules produce duromers.

As Licharz has specia l ised in the manufacture and marketing of semi-f inished products andf inished pa rts f rom t hermo plastics (plasto mers), w e w ill on ly conside r the t hermo plastic g roupan d i ts various sub-groups in the fol low ing. There is adeq uat e l itera t ure a vailab le t hat dea ls w iththe ot her gro ups of p lastics.

2.3 Molecular bonding force

The coh erence of ma cromo lecules is ba sed on chemica l and physical b ond ing f orces.

For po lymer ma terials the se a re:

• the prima ry valency forces a s a chemical bo nding fo rce• the seconda ry valency force (van d er Waa ls fo rces) as a physical b ond ing f orce

The prima ry va lency forces are essent ially respon sible fo r the che mical propert ies of th e plastic,w hile t he seconda ry valency forces are responsible fo r the physical properties and the a l ign mentof t he ma cromo lecules.

2.3.1 Primary valency forces

The prima ry va lency forces tha t a re genera ted b y the bon d dista nce and t he bo nding ene rgycome from t he a to mic bo nd o f the po lymers. The smaller the bo nd d ista nce betw een th e indivi-dua l a to ms in th e polymer cha in , the h igher the bo nding e nergy . The b ond ing energ y is a l so

increased w ith t he number o f b onds of the individua l a tom s.

• If the mo no me rs a re bo nde d w ith o ne a no t he r a t t w opoints (bifunctional) this forms a threadlike, l inearmacromolecule.

• If t he ind iv idua l mo no me rs a re bo nde d a t mo re tha ntw o po ints this produces molecule branches.

• If mo no me rs a re ma in ly bo nde d w ith o ne a no the r a tthree points (tri functiona l) this forms a spat ia l , wea klyor stro ng ly cross-linked ma cromo lecule.



S t r u c


2.3.2 Secondary valency forces (Secondary bonding forces)

The second a ry va lency fo rces come f rom t he int ermo lecula r bo nd s. They consist o f t hree f orces:

1. Dispersion forces

are t he fo rces of a t t raction bet w een t he individual molecules in t he substa nce. These are g reate rthe closer the molecules are to one another. In the crysta l l ine ranges of the semi-crysta l l ineplastics, th ese fo rces a re especially high be cause o f t his. This explains the ir me cha nical supe rioritycompa red to a morpho us plastics.

Increasing t he d ista nces be tw een the molecules dras t ica l ly reduces the f orces. One rea son fo rincreasing dista nces could be vibra tion caused b y heat ing th e polymer mat eria l. But intercalat ingfo reign a to ms bet w een t he molecules (e.g. solvent or w at er) can also increase the dista nce.

By int ercalat ing plasticisers in the mo lecule cha in, this eff ect can b e used to prod uce plastics th a tare rubb er-elastic at room t empera ture.

2. Dipole forces

a re not fo und in all pla stics. They o nly occur if t he a to -mic bon d ha s a s t rong o verw eight ing to one s ide dueto the a l ign ment o f th e a t oms in the g a lvanic ser ies .This ca n o nly ha ppen i f dissimilar pa rtne rs form abond . The more electroneg at ive a t om of a bon d draw sthe e lectron pa ir to w ard s i tsel f ( polarisa t ion) an d adipole is formed. The neighbo uring polarised g roups a t tract o ne a not her because of the uneq ualelectrical charges.

Polymer mat eria ls w ith a d ipole chara cter are g enera lly less soluble (w ith the exception of strongpola r so lvents) and so f ten a t h igher tempera tures than polymer mater ia ls wi thout a d ipolecharacte r. PVC is the m ost sign ificant polymer ma terial w ith a dipole chara cter.

3. Hydrogen bridges

These are b ond s of o pposite oxyge n a nd hydrogen molecules of di f ferent mo lecule chains due tothe ir h igh a f f in ity t o o ne a not her. This type o f b ond is the most s ta ble o f a l l seconda ry va lencybo nds. The hyd rog en b ridg es are on ly dissolved w ith very strong fo rces and immediate ly refo rmth emselves as soon a s the displa cement fo rces cease, rat her like Velcro. The excellent prope rties,

l ike a h igh m el t ing point o r ex traordinary to ugh ness, o f va r ious polymer mat er ia ls such aspolyamides are due t o hydrog en bridges.

Other pure ly physica l in termolecula r b ond s a re ent an glement , loo ping o f cha ins or bo nding inth e semi-crysta l line rang es. These are d escribe d a s net w ork points tha t a l low mo lecule-interlocking pow er t ransmission.

In very thin a nd symmetrical mo lecule cha ins, the second ary valency pow ers are g eneral ly not sopron oun ced, a pa rt f ro m mo lecule part s in the semi-crysta l line rang es. The m olecule cha ins ofpolymer mat eria ls such as this can ea si ly sl ide past o ne a not her i f they a re subject t o m echanicalstress. These ma terials ha ve very go od sliding prope rties, but at th e same t ime the y are subject t ohigh wear due to abras ion , and they have a h igh tendency to creep. Examples o f th is a rePE-UHM W and PTFE.

- + - + - + - +

+ - + - + - + -



S t r u c


2.4 Order of the macromolecules

Thermo plastics a re classi f ied in tw o g roups according to th e ord er of t heir macrom olecules. Adist inction is made betw een

• am orphous th ermoplas t ics w i th comple te ly d isordered ma cromo lecules(w ad ding-l ike st ructure) due to the form of the ba sic uni ts and /or t hea l ignment o f an y side g roups tha t e x ist . Amorphous thermoplas t ics a rehard, brit t le and transparent .

• semi-crysta l line th ermo plastics w ith some high ly ordered , pa ral lel posi-t ioned ma cromo lecule cha ins tha t f orm crysta l lites . A la rg e numb er o fcrysta l l ite s fo rm so-cal led spherulite s. Com plete crysta l l isa t ion ( semi-crysta l l ine pla st ic) is no t po ssible beca use of cha in loo ping d uring po ly-merisa tion. Semi-crysta lline pla stics are to ug h a nd o pa q ue t o w hite.

Semi-crysta l line plast ics have di f ferent propert ies tha n a morpho us pla st ics due to the higher se-

conda ry valency forces. They soft en la ter, ca n b e subjected to more mecha nica l stress, a re more resis-

ta nt t o a brasion, a re toug h-elastic ra ther tha n britt le and a re genera lly more resista nt t o chemicals.

Because of th is, th e semi-crysta lline th ermopla stics a re mo re sig nifica nt fo r eng ineering plastics.

2.5 Alignment of the molecules in the macromolecule

Basically th ere a re th ree d ifferent alignmen t possibilitiesof the substi tute “ R” in the molecule chain.

1. AtacticRand om a lignm ent in the chain

2. IsotacticReg ular, one -sided alignmen t in the chain

3. SyndiotacticReg ularly cha ng ing alignmen t in the chain

The po lymer ma terial can o nly have a crysta lline structure if a regula r chain a lig nmen t e xists for aspecif ic leng th of the complete seq uence. As a result of this, the molecule a l ign ment ha s a d irectinfluence o n t he me chanical propert ies.

2.6 Homopolymers / copolymersPlastics tha t a re polymerised f rom th e sam e mon ome r structural elemen ts are cal led ho mop oly-mers. P las t ics tha t consist o f tw o o r more m ono mer uni ts a re d escr ibed as copolymers. Whencopolymers are b eing prod uced, the mo nom er units are not just mixed, but chemically integ rat edinto the molecule chain. With copolymerisat ion i t is possible to improve specif ic materia lproperties in a ta rgeted mann er.

Essentially, a d istinction is ma de b etw een f our d ifferent t ypes of copolymers:

1. Statistic chain structure (rando m d istribution o f t he d if ferent m onom er units)2. Alternating chain structure (regular chang e of t he different individua l mon ome r units)3. Block-like chain structure (regularly cha ng ing blocks of t he different mon ome r units)

4. Graft polymers (ho mo g e ne o us cha in o f o ne un i t w ith g ra f t e d side cha ins o fa d if ferent unit)

CRC



S t r u c


Ano th er a l terna tive to chang e t he pro perties is to (physica l ly) mix tw o p olymers. The m at eria lsproduced f rom th is are know n as polyblends.

3. PropertiesThe a bo ve-described molecular structure of the plastics produces a rang e o f special prope rties a ndunique chara cteristics. In th e fo llow ing, several of the se w ill be introduced a nd d escribed in moredeta i l .

3.1 Mechanical properties

The me chan ica l prope rties of p lastics a re prima rily de te rmined by t he seconda ry bond ing fo rces.The mo re pronoun ced these are, th e bet ter th e mecha nical properties.

Because of the morpho logical structure o f plast ics, the properties are d epend ent on fa ctors sucha s

• time• temperature• moisture• chemical inf luences

and f luctua te strongly depending on t he inf luence of one o f more fa ctors.

3.1.1 Visco-elastic behaviour

All plastics have a more or less pronounced visco-elasticity. Mechanical stress dissolves thesecond ary bo nds in the m olecule structure, a nd the molecule chains sl ide p ast o ne a not her. Thelonger t he s t ress i s appl ied , the fur ther t he cha ins moveaw ay f rom each o ther.

This mea ns tha t comp a red t o me ta l lic ma te ria ls, pla st icsdeform when subjected to h igh s t ress over a long per iod(r cold f low ). When m aximum expansion ha s been rea ched,th e plast ic sol idi f ies a g a in an d e xpansion is reduced . Thew eaker the second ary bon ds in the ma cromo lecule a re , themore prono unced the se properties are.

A simple m olecule structure w ith no ent an gled side-gro ups,

or a low deg ree of crysta ll ini ty in t he plast ic, encourag es thechains to g lide pa st o ne a not her.

This de fo rma tion is furt her prom ot ed b y therm al inf luences. The mo lecules a re st imulat ed t ov ibra te wh ich l e a ds to g re a te r d i s t a nce s be twe e n the cha ins a nd co nse q ue n t l y to we a ke rsecond ary bo nds. Hence, sta bi li ty values for dimensioning compon ent part s ca nno t b e used a s asing le point value, but ra the r they must be included in the sta t ic ca lcula t ion in rela t ion t o stresstime and thermal ef fects.

3.1.2 Moisture absorption

In pa rt icular plast ics produced by po lyconde nsation (r polymerisa t ion w i th the c leavag e o f e .g .

w at er) have a tend ency to a bsorb w at er from t he surroundings via inw ard dif fusion. This processis a reversible ba lanced rea ction in w hich the m ore w at er w hich is ava ilab le, the m ore th e plasticsab sorb. The intercala t ed w at er molecules increase th e d ista nce betw een t he mo lecule chains and

seconds

days

T e n s i l e f o r c e

Expansion

r

r



S t r u c


w ea ken the seconda ry bond s. The cha ins become moremo bile, wh ich results in a red uction in mecha nica l values anda n increa se in elasticity a s w ell a s swe lling.

In the ca se o f po lyam ides the h ydrog en br idge s do n ot just

ensure excellent mecha nica l prope rties such a s g oo d a bra sionresista nce, mechanical stab il ity a nd to ugh ness, they a lso leadto intercala t ion of w at er in th e mo lecule chains.

As bo th w a t e r a nd the po lya mide mo le cu le s a re ca pa b le o fforming hydroge n br idg es w hen the w a t er has d i f fused in tothe molecule chain, i t separa tes the exist ing hydrog en b ridg ea nd occupies the f ree valences. The w at er molecules make t hepolymer chain sl ightly more mobile which gives room formo re w a te r molecules. This process cont inues unti l thesa t ura t ion point has been reached. When the w a t er concen-tra tion in t he surrounding s falls a ga in, the pro cess is reversed.

Wat er ab sorption is fa voured by increasing tempera tures andhigh a mbient mo isture . By ab sorbing w a t er, the polyamidesbecom e mo re to ug h-elastic a nd less solid a nd rigid.

For a pplicat ions in w hich th ese propert ies a re req uired, i t ispossible to increa se the w a t er concentra t ion by s tor ing t hemat eria ls in hot w at er (r conditioning).

For wa ter absorpt ion through a tmospheric mois ture , i t should be noted tha t the process inth ick-w a l led compo nent par ts only takes place c lose to t he surfa ce and tha t g enera l ly no w a t erab sorption – w ith the d escribed results – should be expected in the inner area o f th e compone nt pa rt.

3.1.3 Chemical influences

Chemica ls can a t t ack and separa te t he pr ima ry an d second ary bon ds o f th e molecule cha ins,w hich can b e seen by sw elling or de compo sition of t he plastic. Sw elling of the p lastic is caused bythe chemical di f fusing into the molecule structure, leading to a loss of stabi l i ty . In a purelychemical a tt ack, the loss of stab ility can occur w ith no n ot icea ble increase in volume or w eight .

The inw a rd dif fusion o f t he f oreign m olecules redu ces the second a ry valency pow ers to such anextent th at th e interna l stresses in th e ma te ria l or externa l forces can ca use (stress) cra cking (rstress corrosion cracking).

3.2 Chemical resistanceCompared to met allic mat erials, plastics have a high resista nce to chemicals. This can b e a tt ribut edto the f ac t tha t the molecules a re l inked through a tomic bonding . Because o f the i r physica lna ture, the seconda ry valency pow ers only play a subordinat e role. Most plast ics are resista nt t oma ny a cids and a lkaline solutions as w ell as a q ueou s salt solutions and solvents.

How ever, oxidising a cids an d o rga nic solvents can be a problem in ma ny cases, but this prob lemcan be resolved by using special plastics.

Resista nce to chemicals decreases as the tem perat ure a nd exposure t ime increase. This can be seenby a n increa se in w eight an d volume a s we ll as a decline in mecha nical values. A lack of resista nceto a specif ic medium can g enera lly be seen by a sw el ling o f the plast ic w i th no a ppreciable

chemical a tt ack, or in a chemical a tt ack w ith med ium to severe sw elling.

R i g i d i t y

Wat er cont ent

E x p a n s i o n

Wat er cont ent

r

r

r

r



S t r u c


3.3 Electrical properties

Because o f the a t omic bon ding o f the i r molecules , p las t ics , unlike met a l lic ma ter ia ls w ith ionbo nds, do n ot ha ve free electron s a nd a re thus classified a s non -conducto rs. How ever, the insula ti-on properties can be g reatly reduced or even completely nega ted throug h w at er absorption a nd /

or th e a dd ition o f met allic fillers, gra phite or carbo n bla ck.

Man y plastics are suita ble fo r use in hig h-freq uency area s as the ir dielectric losses are very low an dthey o nly heat up a li t t le .

Losses in t he a rea o f a pplication should b e

• fo r high f requ ency insulato rs er. t a n d < 10-3

• for high frequen cy heat ing er. t a n d > 10-2

Plastics general ly have a surface resistance of >10 8 Ω . In the event o f f r ic t ion w i th a secondnon-conductor , th is leads to e lectrosta t ic charg ing d ue to e lectron t ransfer a t the b ound arysurface . P las t ics a re not suita ble fo r use in explosion pro tected a rea s wi tho ut a ny conducta ncead ditives, as spa rks can be caused w hen th ey touch ea rthed o bjects.

3.4 Dimensional stability

Increasing hea t o r in terca la t ion o f fo re ign molecules (e .g . w a t er or so lvent ) in the cha in com-pound of the molecule cha ins increases the d ista nce bet w een the chains. This causes the volumeof the plast ic compo nent s to chang e , resul t ing in a chang e in i t s d imensions. Vice versa , a s th esurroundings become colder, or w hen t he w at er concentra t ion decreases, the volume is reducedw hich is accompa nied by t he correspon ding shrinking an d size reduction.

Plast ics a re ge nera l ly forme d or refo rmed t o semi-f inishedprod ucts from t he m elt. As a rule, the semi-finished produ ctsw e ma nufa cture a re th ick-w a l led prod ucts w i th h igh vo lu-mes, such a s sol id rod s, slab s and blocks. As plast ics are ba dhea t conductors , the edges o f the products cool muchq uicker tha n the core. How ever, because of hea t expansion,this has a g reater volume tha n the ed ge s. The out er area ha sa l read y so l id i f ied w i th a loss o f vo lume a nd t he a ssocia tedshrinking. The shrinking of th e core causes inne r stresses th a t“ freez e” a s th e prod uct cools. These stresses can b e mini-mise d by he a t t re a tme n t (r a nne a ling , simila r to stress-freeannealing of steel) . However, some residual stress canrema in. These de crease over a pe riod of t ime d ue t o t he visco-elast ic beha viour o f t he pla st ics(r relaxation).

These residua l s t resses can be re lea sed by o ne-sided m achining or he a t ing a nd can b ecomeob vious throug h dimensiona l chang es or disto rtion.

The a bo ve-described properties of t he plast ics are mo re or less prono unced a nd can b e compen -sa ted an d kept under cont rol rela t ively easily w ith constructive mea sures. But th ey must be a de-q ua tely considered in the d esign of compone nts. The f ol low ing chapt ers dea l with specia l issuessuch as beha viour in f ire , sto rag e, ma teria l-compliant t olerances in compo nent s and m an y oth erfactors.

Warm

core

Solidified jacket



B e h a

v i o u r i n f i r e

1. Behaviour of plastics in fire and fire ratings

Gene rally, plastics are o rga nic substa nces or mod ifications of org a nic substa nces, w hich, like ot herorga nic substances a re threa tened by cha in breakag e , cleavage o f subst i tu tes and ox ida t ion a t

high t empe rat ures. Theref ore, a pa rt from a few except ions, plastics a re more or less combu stiblew hich is some thing tha t ca n b e a serious technical problem in th e specific use o f pla stics.

1.1 Combustibility

If plast ics are hea ted local ly or over large surfa ces to ab ove th eir specif ic decomposit ion t empe-rat ure, they relea se volat ile, low molecular constituent s. In ma ny cases to g eth er w ith the a mbientoxygen, t hese form a f l ammab le g as mixture w hich can igni te i f a n igni t ion source i s ad ded andan ad equa te supply of o xygen is avai lab le.

The a mount o f hea t tha t i s fed in an d t he vo lume o f the combust ible surface tha t th is can a f fecta re b ot h very signi f icant for t he evolut ion o f a f i re a nd the course o f the f i re . Anot her decisive

fa ctor is the a tmo spheric oxygen concentra tion.

For instance, it is possible tha t a large q uan ti ty of hea t w hich a f fects a larg e volume w ith a largesurface a rea but a lack o f o xygen o nly leads to pyro lyt ic cleavag e in the beg inning (r relea se ofh ighly f lam ma ble , vo la t i le a nd low molecula r const i tuents). If o ne a dd s oxygen in the r igh tconcentra tion, unde r unfavoura ble cond itions this can result in a d eflag rat ion or an explosion.

How ever, wi th the same volumes an d a low er hea t input , a s wel l a s an a deq ua t e ly h igh oxygenconcentra tion, th e same substan ce only burns slow ly.

Becau se of t his be ha viou r, it is very diff icult, if not impossible, to ma ke an y fire-te chnica l fo recasts.

1.2 Conflagration gases

As with t he comb ustion o f o the r substa nces, w hen plast ics burn they produce various conflag ra-tion g a ses. As a rule, these are said t o b e high ly to xic. This is no t a bsolutely correct a s, on t he o nehan d, the toxicity depend s on the t ype and q uant i ty of the plast ic involved in the f ire a nd, on theot her, all conflag rat ion ga ses resulting from a (substa nce-independ ent ) fire shou ld be rega rded a stoxic.

One example is the con flag rat ion ga ses resulting f rom t he incineration o f polyethylene, w hich, inad di t ion t o sma l l q uan t i t ies o f soot an d low molecula r p las t ic const i tuents , a lmost exclusive lyconta in ca rbon mono xide , ca rbo n d ioxide and w a t er. This i s comparab le w i th the conf lag ra t ionga ses tha t occur when w ood or stea rine are burned.

On the o ther hand, when polyv iny l chlor ide i s burned, there i s a danger o f chlor ine be ingre leased, which in combina t ion wi th a tmospheric mois ture or ex t inguishing wa ter forms tohyd rochloric a cid.

Many plast ics prod uce a lot o f soot w hen t hey burn, w hich ma kes i t di f f icult f or the f ire briga desto rea ch the sou rce of t he f ire. These plastics include t he po lyolef ins PE a nd PP a s w ell a s styrenepla stics such a s PS a nd ABS.

This must b e con side red fo r de sig ns in fire-critical a rea s.

Behaviour in fire



B e h a

v i o u r i n f i r e

1.3 Behaviour in fire

Almost a ll plastics a re com bu stible. Except ions to th is a re PTFE a nd silicone s, w hich a re virtu a llynon -combustible. Most plast ics continue to b urn a f t er they have bee n ig nited a nd t he source ofignit ion has b een removed. Several extinguish w hen the ignit ion source is removed, w hile o thers

canno t be ig ni ted . In ma ny cases, the plas t ic mel ts due t o th e hea t o f combust ion and formsburning d roplets w hich can promo te t he sprea d o f th e f ire . The de g ree of comb ustibi li ty can b ereduced by a dding the corresponding ad dit ives.Add itives ba sed o n th e fo llow ing mecha nisms are used:

• EndothermyThe t emperat ure of the plast ic is reduced b y the decomposit ion o r vaporisa t ion of the ad dit ive.This is possible f or exa mple w ith w a te r sto res (a luminium hyd roxide ) or ph ospho rous com-pounds being a dded to t he plast ic.

• Radical bondingThe rad icals that form during the f ire a re bond ed b y the a ddit ive, w hich slow s dow n the thermaldecomp osition an d consequen tly the release of f lamma ble, volat ile constituent s.

• Formation of heavy gasesHeavy ga ses are formed t hrough t he th ermal ef fects on t he a ddit ive, preferab ly halogens, w hichshield the plastic from a tmo spheric oxygen a nd t hus prevent oxidat ion.

But t he use of f ire reta rding a dd itives do es not ma ke pla stics no n-comb ustible. Only plastics th a tare rega rded a s being no n-f lamma ble are suita ble for applicat ions that dema nd no n-combustibi-lity o f t he pla stic.

1.4 Fire ratings

Often , to assess how plast ics beha ve in f i re , imprecise t erms such as “ h ighly f lam ma ble” or“ f i re resis tant ” or “ non comb ust ible” a re used. These terms inadeq ua t e ly re f lect th e ac tua lbeha v iour o f the plas t ics and only provide a l imi ted in ference for t he usab il ity o f a p last ic for aspecific applica tio n. To a ssess ho w plastics be ha ve in fire in the a rea s of electro-techno log y, tra ff ic,bui ld ing , e t c . the re a re current ly approx . 700 na t iona l and in terna t iona l test me tho ds . In th eelectrica l secto r th e m et ho d UL 94 HB or UL 94 V from Und erw rite rs La bo rat ories (USA) hasbecome t he most w idely accepted . These tests re fer to t he burning t ime a nd t he burningbe ha viou r of plastics. In t est UL 94V a d ist inct ion i s ma de b etw eencla ssificat ions V0 to V2, V0 be ingthe most fa vourab le ra t ing.

Ano th er possibi l ity o f comp a ringth e f lam ma bil ity of plast ics is th eoxygen index . In a contro l lable

O2/N2 mixture a vert ica l plast icsample i s igni ted and the mini-mum volume o f O2 required tobu rn t he p lastic is mea sured. Thistes t a l so a l lows the e f fects o ff l a me re t a rda n t s to be o bse rv e d .The diag ram oppo si te cont a insseveral oxygen indices for com-parison.Index values ≤ 21% can lead tocontinued burning a f t er the sour-ce of ignit ion ha s been removed.

PA 6

PA 66

POM

PET

PC

PE

PP

PVC

PVDF

PTFE

PSU

PEI

PEEK

Oak (as a comparison)

0 10 20 30 40 50 60 70 80 90 100Oxygen index (%)



R e s i s

t a n c e t o r a d

i a t i o n a n d

w e a t h e r i n g

Resistance to radiation and weathering

1. Plastics’ resistance to radiation and weathering

Changes in plas t ics due to wea ther ing e f fects and h igh-energy rays a re o f ten descr ibed as»ag ing«, w ith referen ce to the process of biolog ical d eg rad at ion. This is q uite a n a ccurat e d escrip-

tion since plastics, as orga nic ma terials, do n ot just ha ve an a na logy to na tura l substa nces in theirconstituen ts but also in their ma cromo lecular structure.

The pa ra l le ls a re a lso ob v ious by the f a c t tha t w e o f t en speak o f the “ l ife ” o f a p las t ic product .The d ura t ion i s de t ermined by t he d ecomposit ion o f t he plas t ic. It ma y be re la t ive ly long com-pa red t o o the r nat ural substa nces, but it is still limited .

1.1 Radiation

The m a jori ty of plast ics are subject t o d ecompo sit ion or a cross-l inking o f t he m a cromolecularst ructure w hen a f fected by h igh-energy rad ia t ion . The chang es in th e mo lecula r s t ructure th a ta ctually occur depend o n the a tmo spheric oxygen.

When oxyg en is present , ge nera lly oxida tive de comp osition o f t he p lastic occurs. This is especiallythe case w hen the dose of rad ia t ion is small, the surfa ce area of the prod uct is large a nd t he w allsa re thin. Under these prerequisites, the a tm ospheric oxygen ha s sufficient t ime to d iffuse into t heplast ic and t o occupy the valences that are ma de free b y the radia t ion.

In t he a bsence o f o xyge n, the plast ic is part ia l ly decomposed b y the ma in chains breaking up a ndpa rtia l ly cross-l inked. G enera l ly decom posit ion a nd cross-l inking reaction s happe n a t t he sam etime, altho ugh o ne of t he reactions is strong er.

In a ny ca se, the cha ng es in th e plastics caused by rad iation a re accompa nied by a loss of m echan i-cal propert ies such a s mechanical sta bi l ity , rigidi ty an d ha rdne ss or bri t t leness. P la st ics tha t a resubject t o cross-l inking can experience a cha ng e in propert ies even lead ing t o a rubb er-elast iccond it ion. Beside s th is, during b ot h th e cross-l inking a nd d ecomp osit ion of th e plast ics, sma lla moun ts of g aseous substa nces such as carbo n mono xide o r carb on d ioxide are relea sed.

Atte ntion should be paid to the fa ct that the de scribed chang es are very gradua l and tha t there isno sudde n, unan nou nced chang e in properties. The eff ects of ra diat ion on plastics depe nd o n thegeometry o f the component , dosage , mechanica l s t ress , tempera ture and the surroundingmedium. Therefore, it is not possible to make a gen eral ised sta t ement ab out the da mag ing dosesfo r individu a l plastics.

1.2 Weathering effects

Wea thering resista nce i s ma inly eva lua te d by t he v isua l chan ge o f the surface . How ever, th isleaves the question unanswe red as to how the mechanical values change. On t he one hand , it can-not be ruled o ut t hat plast ics wh ich are no t subject to any g reat v isual chang es have a serious lossof mechanical properties and , on the ot her ha nd, plast ics with considerable visual chang es suf ferno g re a t l o ss o f me cha n ica l p ro pe r t i e s. Bu t to e v a lua t e w e a the r ing re si st a nce co r re c t ly, themechan ical properties must be a mea sured. Some results of w ea the ring are a decl ine in sta bi li tyan d h ard ness as w ell as a n increa se in elasticity or brittleness. The surface o f t he plastic can app ea rblea ched o r oxida tively decomp osed o r stress cra cks can f orm.

The chan ge s in plas t ics as a result o f w ea t her ing a re m ainly caused by th ermal a nd ph ot o-oxi-da tive rea ctions a s we ll as by t he intercalat ion of w at er molecules in th e plastic’s cha in structure.

UV rays and w arming b y d i rect sunl igh t lead to cha in de composit ion a nd f ree va lences tha t a re

satura ted by oxygen d iffusing inw ard s. The surfa ce becomes yellow or bleached .

In the case of semi-crysta l l ine plast ics there could be secondary crysta l l isa t ion result ing inincreased ha rdness a nd rigidity. Conseq uent ly th ese pla stics a re also mo re brittle and lose a larg epa rt of t heir ela st ici ty. Froze n residua l stresses from th e ma nuf a cturing process can relax and



R e s i s

t a n c e t o r a d

i a t i o n a n d

w e a t h e r i n g

cause defo rmat ion thro ugh the e f fects o f w arming – simila r to an an nea l ing process. This i sespecia lly serious for th in-w a lled f inished pa rts.

By absorbing w at er, the plastics become to ug h-elastic a nd sta bility and rig idity de cline, wh ich canalso be a prob lem with t hin-w alled finished pa rts.

Weat her ing resista nce can be improved w i th ad di t ives – in a simila r w ay t ha t f i re re ta rda nta dd itives are used. How ever, it is not possible to provide a complete prot ection a ga inst d ecompo -sit ion caused b y the ef f ects of w eat hering.

Unfor tuna t e ly no va l id t est ing s tanda rd or sta nda rd paramet ers a re def ined rega rding a r t i f ic ia lw ea t her ing an d i t s va r iables tha t could be used t o compa re resista nces. How ever it can be sa idtha t p las t ics tha t have been co loured wi th ca rbon black or s tabi l i sed aga inst UV rays wi tha d d i t iv e s a re mo re s t a b le a g a inst l ig h t a nd w e a t he r ing e f f e c t s tha n l ig h t co lo ure d o r na tura lcoloured g rad es. Except ions to t his a re PVDF a nd PTFE, w hich have o ut sta nd ing resista nce to lig htand w eat hering e f fects even without colouring o r add it ives.

When eva lua t ing w ea ther ing resista nce , i t should a lso b e remembered t ha t chang es caused b yw ea the ring e ffects are gen erally in the surfa ce areas of the pro duct. Deeper layers are usua lly nota t ta cked, so t hat thick-w alled pa rts are less a f fected b y change tha n t hin-w alled pa rts.



S t o r a

g e i n f o r m a

t i o n

Storage information

Information for material-related handling of plastics at receipt and in storage

The m a te ria l properties an d special fea tu res of plastics de scribe d in th e previous section s clea rlyillustra te t ha t plastic products can suffer unw an ted q uality losses due to e nvironmen ta l effe cts.

Therefo re to ma inta in the h igh q ua l ity a nd f unct iona l ity o f our products – a lso o ver longerperiods – several factors should be considered w hen ha ndling an d storing the m.

1. P las t ics become b r it t le a t low tem pera t ures and become ha rd , less e las t ic and sensit ive t oimpact. In th is condition t he d an ge r of b reaking or splitting t hroug h externa l forces is very high– especia l ly for f inished prod ucts. Cold pla st ic prod ucts sho uld never be t hrow n, shaken o rdropped.

2. The prop erties of plast ics can cha ng e due to w ea the ring ef f ects. The ma teria l propert ies cansuf fer i r reversible neg a t ive e f fects throug h sunlight , a tmo spheric oxygen an d moisture (e .g .bleaching a nd/or oxidat ion of t he surface, w at er ab sorption, et c.). If t he prod ucts are subject t o

di rect sunl ight or one-sided he a t , there is a da ng er o f permanent d e forma t ion throug h hea texpan sion a nd relea sed interna l residua l stresses. Theref ore f inished prod ucts sho uld no t b esto red out do ors an d semi-f inished products should be sto red out do ors for as short a period aspossible.

3 . P last ics ha ve scrat ch sensit ive surfaces. Sharp e dg es on shelves, na i ls in p a l let s, la rge dirtpar t ic les be tw een t he prod ucts and o t her sharp ob jects can cause scra t ches an d/or g rooves,w hich in turn can cause breakag e a nd notching. When t ransporting a nd storing plast ic productsit sho u ld b e e nsure d t ha t the surf a ce re ma ins sc ra t ch a nd g ro o v e f re e a nd tha t no ro ug hparticles are a llow ed t o a dhere to the surface.

4. Not a ll plastics a re eq ua lly resista nt t o chem ica ls, solvent s, oils or fa ts. Severa l a re at ta cked b ythese substa nces, w hich can lead to surface opa city , sw el ling , decomposit ion a nd permanentchang es in the mechanica l propert ies. Therefo re , substa nces tha t can a t t ack and d am ag eplastics must b e kept aw ay from the prod ucts during storag e.

5. P la st ics are subject t o reversible dimensiona l cha ng es wh en a f fected by extreme te mpera turef luctua tion s due t o shrinking or expa nsion . Dimen sion checks can o nly be ca rried o ut imme-diately on receipt of the g ood s if the prod ucts are a t roo m temperat ure (≈ + 23° C). Prod ucts w itha h igher or low er tempera ture could produce incorrect mea sured va lues due to shr inkag e orexpansion of the plastic. Too w a rm/cold products must b e stored tem pora rily in a d ry pla ce andbe brought up/dow n t o roo m t emperature b efore d imensions are checked.

6. Because o f t he product ion process, p last ics, a nd f in ished products manuf actured f rom them ,can ha ve residua l st resses , in spite o f an nea l ing . These have a ten dency to re lax w hen t he

produ cts are stored fo r long periods and subjected to tem perat ure effects (e.g. d irect sunlight ).Po lyam ides a lso t end t o a bsorb w a t er w hen t he humidi ty is h igh , w hich in turn causes thevolume to increase. These processes are ge nera l ly accom pa nied by dimen sion a l a nd sha pechanges due t o d e format ion .

Therefo re for long -term stora ge w e recomm end closed b oxes a nd consta nt cond itions (≈ s tandardclimat e + 23° C/50% RH). The e xpected dimen sion a l a nd sha pe cha ng es are t hus kept t o a minimumand gene ral ly have no ef fect on the f unction of t he product .



Plastic friction bearings



P l a s t i c f r i c t i o n b e a r i n g s

1. Use of thermoplastics for friction bearings

Req uiremen ts for a f riction b ea ring ma terial such as

• Go od sliding a nd emerg ency running properties• Wea r resista nce• Pressure resistance• Lon g life• Heat d ef lection temperat ure

a re ea sily fulfilled by t od ay’s mod ern th ermoplastics.

Plastics a re especia lly used w here

• Dry runn ing o r mixed f riction occurs• Specia l plastic-specific prope rties a re req uired• Low manuf acturing costs are advanta geo us even with low qua nti t ies

The fo llow ing plastic-specific prope rties are especia lly valued :

• Go od sliding pro perties• Low coefficient s of friction• Hig h w ea r resista nce• Goo d da mping properties• Low w eight• Goo d d ry and emerg ency running properties• Corrosion resista nce• Chemical resista nce• Low ma intena nce aft er initial one t ime lubricat ion

• Physiolog ica lly sa fe in some cases

Disadvan ta g es such as low hea t cond uctivi ty, tempe rat ure-depe nde nt sta bi li ty values, rela t ivelyhigh hea t expansion, creeping w hen subject t o long -term stress a nd in some cases the t end ency toab sorb mo isture can b e kept und er control to a grea t e xtent by ma teria l-rela t ed design measures.

1.1 Materials

Of t he larg e num ber o f plast ics tha t a re ava i lab le, those w ith semi-crysta l line or high crysta l linemo lecular structures are mo st suita ble fo r use a s sliding elemen ts. Several ma terials belon ging tothis group, a nd how the y ha ve been mod ified fo r slide app lications, are listed in Tab le 1.

Plastic friction bearings




Material Short description Property

Po lya mid e 6 ca st PA 6 G Hig h a bra sio n resist a nce

Po lya mid e 6 ca st PA 6 G + Mo S2 Hig her crysta llinity th a n PA 6 G+ Molybden um disulphide

Oilamid®

PA 6 G + O IL Hig he st a bra sio n resist a nce, lo w co eff icie ntof f riction

Calaumid ® 1200 PA 12 G Hig h a b ra sio n resist a nce, h ig h lo a d bea ringstrength

Po lya mid e 6 PA 6 Medium a b ra sio n resist a n

Po lya mid e 66 PA 66 Hig h a bra sio n resist a nce

Po lya ce t a l (Co po lymer POM Medium a b ra sio n resist a nce, co mpressio nresistant

Polyethylene terephthalat e PET Hig h a bra sio n resist a nce, lo w co eff icientof friction

Polyethylene terephthalat e PET-GL Hig h a bra sio n resist ance, very lo w co eff icient

a nd lub rica nt o f f rict io nPo lye t hylene UHMW PE - UHMW Lo w co eff icient o f f rict io n, lo w rig id it y,

acid-resistant

Polytet raf luoroe th ylene PTFE Very g oo d sliding prop erties, low rig idity

Polytet rafluoroe thylene Partially go od sliding propertiesa nd g la ss f ib re PTFE + G la ss g o o d rig id it y

Po lyt e tra f lu oro e th yle ne PTFE + Co a l Ve ry g o o d slid in g p ro pe rt ie s, g o o d rig id it yand coa l

Polyetheretherketone PEEK Hig h pv, h ig h lo a da bilit y, hig h price

Po lyet heret herket one PEEK - G L Best slid ing pro pe rt iesmodif ied hig hest pv va lue a nd hig hest price

Tab le1: Friction b ea ring ma terials and propert ies

1.2 Manufacture

Friction b ea ring s can be ma nufa ctured by ma chining or injection moulding. Polyamide bea ring smanufactured by in ject ion moulding a re much less wear res is tant than those produced byma chining due t o t heir amo rpho us propo rtions in th e mo lecular structure. The f ine crysta l linestructure o f the low s t ress polyamide semi- f in ished products manufactured by cas t inggua rantees optimum w ear resista nce.

Compa red to in ject ion m oulded f r ic t ion b ea r ing s, machined bea r ing s a llow high dimensiona lprecision . The high m a chining pe rfo rma nce of conven tion a l ma chine t oo ls, la th es and CNCprocessing centres a l low th e cost-ef f ective ma nufa cturing of individual pa rts as we ll a s small to

med ium sized ba tches. Flexible, a lmo st l imitless desig n possibi l it ies, especia l ly fo r t hick w alledparts are anot her advant ag e of ma chined frict ion bea rings.

1.3 Sliding abrasion/mating

Sliding a bra sion is prima rily depend ent on t he ma terial

a nd surface propert ies of t he ma ting compo nent . The

most fa vourable mat ing compo nent f or pla stic ha s pro-

ven to be ha rdened steel wi th a minimum ha rdness of

50 HRc. If surfaces w ith a low er ha rdness a re used t here

is a da nger o f rough t ips breaking o f f an d caus ing in-

crea sed plastic/met a l a bra sion in friction bea ring s.

The influence o f surfa ce roug hness on sliding ab rasionand the sliding frict ion coeff icient can b e evaluat ed indi f ferent w ays . For t he mo re ab ras ion resista nt , lessroug hne ss sensi t ive p last ics (e .g . PA a nd POM) i t ca n

C o e f f i c i e n t o f s l i d i n g f r i c t i o n µ

Average dept h of roug hness µm

POM

PA

Figure 1

0,20 2 4 6

0,4

0,6




be ob served th at the sl iding f rict ion coeff icientis rela t ively high, especia l ly for part icularlysmoo th surfaces (Figure 1).

As the roughness increases, i t is reduced to a

minimum and then increases aga in in thefurt her course. The sl iding a bra sion b ecome shigher w ith increa sing roug hness.

On the o the r ha nd , the mo re a bra s io n sus-cep t ible pla stics (e.g . PE-UHMW, PTFE) sho w asteadily increasing sl iding frict ion coeff icientw ith increa sing roug hne ss. The ra ng e in w hichth e sliding f riction coef ficient improves w ith increasing rou g hne ss is minima l. The sliding a bra sionincreases w ith increa sing roug hness.

The mo del idea to explain t his beh aviour assumes tha t a bra sion in frict ion b ea ring s takes over a

lubrica t ing funct ion . I t can be observed tha t a f avourable s l id ing condi t ion ex is ts when theq uant ity and fo rm of abrasion are optimum.

With th e plast ics tha t are less sensit ive to roug hness, ad hesion forces and ad hesive bridges ha vean ef f ect in the low roughness rang e of the ma ting component. Due to the smooth surfa ce, thereis no g rea t ab ras ion t ha t can ta ke over the lubr ica t ing funct ion . As roug hness increases, themovement -hindering forces decrea se so t ha t the sl id ing f r ic t ion coef f icient improves w i th in-crea sing a bras ion . From a specif ic deg ree o f roug hness, the plast ic begins to a brad e , w hich re-q uires high er movement forces. The a mount of ab rasion exceeds the opt imum. Because of thesemechan isms, the sliding friction coefficient det eriora tes.

As th e opt imum a bra sion volume is very small w ith th e plast ics th a t a re sensit ive to ro ug hness,th ese plast ics only have a very narrow rang e in w hich the sl iding b eha viour can b e improved byab ras ion . With increasing rough ness, the e f fects o f t he a bra sion become p redomina nt . I t is nolonger po ssible to improve the sl id ing b eha v iour. On the o t her ha nd, b y th is to ken the s lid ingbeha viour only w orsens due to a lack of ab rasion on mat eria ls tha t ha ve mating components w itha n extremely smoot h surface.

The surface roug hness of t he plast ics plays no role in t his ob servation, a s they a re sof t comparedto t he meta ll ic ma ting component and q uickly ad apt to i ts conta ct patt ern. Hence, importa nt fo rchoosing the surface q uality of the steel sliding surface is the q uestion w hethe r the f unctiona l ityof t he sliding element is a f fected by ei ther the a mou nt o f sliding ab rasion o r the sliding f rict ioncoefficient . For comb ination w ith plastic friction b ea ring s, the ma ting compon ent s in Tab le 2 w iththe a ssocia t ed surfa ce g rades can be recommended:

Tab le 2: Recommende d surface q ualities for ma ting component s

Low surface h ardn ess an d sma l ler/grea ter surface roug hnesses tha n t hose speci f ied promot esliding a bra sion in the b ea ring an d t hus short en its useful life.

PA 6 G PA 12 G PA 6 PA 66 PA 12 POM PET PE- PTFEUHMW

Mating Hardness

component HRc min. 50 50 50 50 50 50 50 50 50

hardened

steel Rz [µm] 2 – 4 2 – 4 2 – 4 2 – 4 2 – 4 1 – 3 0,5 – 2 0,5 – 2 0,2 – 1

Mating Ma t eria l POM POM POM POM POM PA PA/POM PA/POM PA/POM/PETcomponent

thermo- Rz [µm] 10 10 10 10 10 10 10 10 5plastic

Averag e dep th o f roug hness µm

PET

PE-UHMW

0,6

0,4

0,2

Figure 2

0 2 4 6

C o e f f i c i e n t o f s l i d i n g f r i c t i o n µ




In a dd it ion t o t he a bo ve-ment ioned f a c tors, running speed, sur face pressure and tempe ra turealso h ave a n ef f ect on sl iding ab rasion. High running speeds, surface pressure and tem perat uresalso increase sliding abrasion.The f ollow ing t ab le cont ains guiding va lues fo r the sliding ab rasion of plastics.

Tab le 3: Sliding ab rasion o f p lastics

Material Sliding abrasion Material Sliding abrasionin µm/km in µm/km

Oilamid ® 0,05 POM-C 8,9

PA 6 G 0,1 PET 0,35

PA 6 0,23 PET-GL 0,1

PA 66 0,1 PE-UHMW 0,45

PA 12 0,8 PTFE 21,0

The stat ed values de pend o n the sliding system an d can a lso chan g e due t o chan g es in the slidingsystem p ara met ers.

1.4 Lubrication/dry running

At present th ere a re no g ene ral val id lubrica tion rules for plast ic frict ion b ea ring s. The sam elubricants th a t a re used fo r meta l lic f r ic t ion bea r ing s can a lso be used fo r p last ic bear ings . It i sad visable to use a lubrican t d espite t he g oo d dry running propert ies of p last ics, as the lubricantreduces th e coefficient o f friction a nd t hus the frictiona l hea t. In ad dition, continuo us lubricationalso helps dissipate h ea t f rom th e bea ring . Lubricat ing th e frict ion b ea ring s gives the m a higherload bea r ing capaci ty and reduces w ea r, w hich in turn g ives them long er life . How ever, if t hebea ring s are t o b e used in a very dusty application it is a dvisa ble not to use any lubrication , as the

dust par t ic les become b ond ed in the lubr icant a nd can f orm an ab ras ive paste w hich causesconsiderable w ea r. The plas t ic bea r ing ma ter ia ls recomme nde d in the ta ble on pag e 53 a reresista nt to most comm only used lubrica nts.

An a lterna tive to extern a l lub rica tion a re plastics w ith self-lubrica ting prop erties such a s OILAMIDan d PET-GL. Due to the lubr ican ts tha t a re in teg ra ted in to t he plas t ic, the se ma ter ia ls ha ve thelow est w ear ra tes as w el l a s excel lent dry and emerg ency running prope rt ies. When d esignreasons require to do so, it is also po ssible t o o perat e plastic friction b ea ring s witho ut lubrica tion.

How ever, at ten tion mu st b e pa id tha t t he loa d values are w ithin the pv values sta ted in Tab le 4. Ina ny case, a one t ime lubrication shou ld be carried out during insta l la t ion i f po ssible, even i f thebe a ring s w ill run dry . This conside rab ly improves th e start -up be ha viour a nd ca n prolon g t hel ife o f t he prod uct . It is a l so possible t o lubr ica t e t he b ea r ing s subseque nt ly a t in terva ls to b edetermined empirically.

1.5 Contamination/corrosion

The s tee l sha f t o f f r ict ion b ea r ing s tha t a re opera t ed in dry running condi t ions i s in dang er o fcorroding d ue to migrat ing mo isture. When the surfa ce of t he mat ing compo nent is da ma ged bycorrosion, t his increases sliding ab rasion a nd ca n cause the bea ring to ma lfunction premat urely.This can be prevent ed b y sea l ing t he be a ring ag ainst moisture. Other ef fective measures a re top la t e the ma t ing co mpo ne n t w ith chro mium o r to ma nuf a c ture the ma t ing co mpo ne n t f ro msta inless steel.

Because of t heir low coeff icient s of sliding frict ion, plast ic frict ion b ea ring s tend to suf fer muchless from frictiona l corrosion t ha n met a llic be aring ma terials. Wea r ca used by f rictiona l corrosioncan be red uced even fur ther by lubr ica t ion . Compa red to met a l lic bea r ing m at er ia ls, w ea r inplast ic f r ic t ion bea r ing s caused by cont am ina t ion such as dust o r a bras ion i s much low er, a splast ics, an d e specia l ly polyamides, ha ve the ab ili ty to embe d d ust part icles and thus prevent the




ab rading ef fects. When o perat ing in environment s with high dust levels, it is recomm ended tha tthe bea r ing i s f i t ted w i th lubr ica t ion g rooves. The lubricant conta ined the re binds the dustpart icles and keeps them aw ay from the slide zo ne.

1.6 Load limitsLoa d l imi ts for thermo plas t ic f r ic t ion bea r ing s a re def ined by t he compressive s t rengt h a ndbea r ing tempera t ure . The b ear ing t empera ture i s d i rect ly re la t ed t o t he running speed a nd t heam bient te mpera t ure , an d, w i th dynamica l ly st ressed f r ict ion bea r ing s, a l so to the d ura t ion o fopera t ion . The ma t ing compo nent s , the ir sur face qua l ity and the chosen type o f o pera t ion(lubrica t ed o r unlubrica ted ) a lso ha ve an e f f ect on t he be ar ing te mpera t ure o f a thermoplas t icfriction bea ring .

Tab le 4 con ta ins guiding values for ind ividua l pla st ics. For sta t ica l ly loa de d b ea ring s or frict ionbea ring s w ith very low running speeds, the figures for sustained pressure loa ding can b e app lied.For dyna mica l ly loa ded be aring s, usua lly the pv value (prod uct of surfa ce pressure a nd a verag erunning speed) is used as a cha racteristic variab le. It must b e no ted tha t t his value is not a m at eria l

chara cteristic va lue, as the load limit of the plastics depe nds on t he a bo ve-ment ioned variab les.

Tab le 4: Material g uiding values

Sustained pressureload static MP aNot eq uipped w ith cham-

bers, De fo rma t io n < 2% 23 20 24 15 18 10 22 35 33 5 5 12 57 68

Equipped w ith cham -bers; Def o rma t io n < 2% 70 60 - 50 60 43 74 80 75 20 20 - 105 120

Coefficient of friction µ 0,36 0,18 0,40 0,38 0,35 0,32 0,30(a vera g e va lue) - - - - - - 0,30 0,25 0,2 0,29 0,08 0,1 - 0,11Dry running o n steel 0,42 0,23 0,60 0,42 0,42 0,38 0,38

pv-guiding valueMPa . m/sDry running /Installation lubricationV = 0,1 m/s 0,13 0,23 0,12 0,11 0,13 0,08 0,15 0,15 0,25 0,08 0,05 0,40 0,34 0,66V = 1,0 m/s 0,08 0,15 0,10 0,07 0,08 0,10 0,10 0,15 0,05 0,22 0,42Continuously lubrica ted 0,50 0,50 0,35 0,40 0,50 0,50 0,50 0,50 0,50 0,40 0,40 0,50 1,0 1,0

Coefficient of thermalexpansion+ 20°C bis + 60°Cin 10-5 . K-1 8 8 10 9 8 10 10 8 8 18 20 11 5 4,5

Maximum permissiblebearing temperature incontinuous operation

(RF< 80%) + 90 + 90 + 90 + 80 + 90 + 80 + 90 + 80 + 90 + 50 + 160 + 200 + 250 + 250

Moisture absorptionin % a t 23° C/50% RF 2,2 1,8 0,9 2,1 3,1 0,8 0,2 0,2 0,2 0 0 0 0,2 0,14when sa tura tedin w a ter 7,0 7,0 1,4 10 9 1,5 0,8 0,5 0,4 < 0,01 < 0,01 < 0,01 0,45 0,3

P A 6 G

O i l a m

i d ®

C a l a u

m i d ® 1 2 0 0

P A 6

P A 6 6

P A 1 2

P O M - C

P E T

P E T - G

L

P E - U H

M W

P T F E

P T F E

C o a l

P E E K

P E E K - G L



2. Constructional design

2.1 Bearing play

When d esigning f r ic t ion bea r ings , a d ist inct ion i s ma de b etw een o pera t ing play h 0, insta l la t ion

play he and manuf acturing play h f (see Fig ure 3).

• The o pera ting play (basic play o r minimum play)h 0 is the minimum clea rance th at must exist un derthe most unfavourable condit ions to prevent t hebea ring f rom sticking .

• The insta l la t ion play h e i s the c learance in aninsta lled but no t yet w arm operating sta te .

• The ma nuf a cturing play h f is the measure des-cribing the excess size tha t t he interna l diam ete ro f th e be a r ing must ha v e co mpa re d t o the sha f td i a me te r to e nsure o pe ra t ing p l a y unde r o pe -

rat ing cond itions.

The req uired opera t ing b ea r ing play h 0 can be seen in Diagram 1 . I f guiding requirementsare h igh er, the b ea r ing play can be less. Li tera ture recommend s the fo l low ing a s a ca lcula t ionbasis

h 0 = 0,015M d w

whe reh 0 = operating b earing play in mmd w = spindle diam ete r in mm

However , for a r i thmet ica l de termina t ion , the

precise o pera t ing condi t ions must be know n, a so t herw ise the tem pera ture and moisture e f fectscannot be ta ken fully into account.

2.2 Wall thickness/bearing width

The w a ll thickness of the rmopla stic friction bea ring s is very importa nt in rega rd to the go od insulat i-

on propert ies of the pla st ics. To ensure a deq uat e hea t dissipat ion a nd go od dimensiona l sta bi li ty,

the f r ict ion b ea ring w a l l must be th in . How ever, the bea ring w a l l thickness a lso de pends on th e

a moun t a nd t ype of loa d. Bea ring s w ith high circumferent ial speed s a nd/or high surface pressures

should have th in wa lls, w hile tho se w ith high impact loa ds should b e thicker. Dia g ram 2 show s the

bea ring w a ll thicknesses tha t w e recommend in relat ion to t he sha ft d ia meter and t he type of load .

Where thermoplas t ic f r ic t ion bea r ing s a re to be used as a replacement for b ear ings mad e f romot her mat er ia ls, the w a l l th icknesses a re ge nera l ly de f ined by th e ex ist ing sha f t s and bea r ing

housings. In cases such as this, a t tentionshould be pa id tha t the minimum wa l lthicknesses in Diag ram 2 are ma inta ined. Toprevent a bui ld-up o f hea t in the centre o fthe f r ic t ion bear ing i t should be ensuredtha t i t is in t he ran g e of 1 – 1.5 dw w h e n t hebea r ing w idth i s be ing de te rmined. Expe-r ie nce ha s sho w n tha t a be a r ing w id th o fa ppro x. 1.2 dw is ideal to prevent an accumu-

lat ion of heat in the middle of the bearing.

D

he

hf

ho

he

Figure 3: Diag ram of dif ferent b earing play

0

0 10 30 50 100 150 200

0,1

1,0

0,9

0,8

0,7

0,6

0,5

0,4

0,3

0,2

Interna l diamet er of bearing in mm

h 0 i n % i

n r e l a t i o n t o i n t e r n a l

d i a m

e t e r o f b e a r i n g

H i g h i

m p a c t

l o a d

i n g

N o r m a l

l o a d i n g

H ig h r u n n i ng s

p e e d

B e a r i n g w a l l t h i c k n e s s i n m m

Shaf t diamet er in mm

0 20 40 60 80 100 120 140 160 180 200 220 240 260 0

5

1 0

1 5

2 0

2 5

3 0

3 5

4 0

Diagram 1: Req uired opera ting bea ring play

Diagram 2: Recommended bea ring w all thickness





2.3 Allowances

For f r ict ion be ar ings tha t a re to b e used in env ironment s w ith h igh tem pera t ures, a cer ta indimensiona l change due to thermal expansionsho u ld be a l l o we d f o r whe n the be a r ing i s be ing

dimensioned.

The e xpected dimensiona l cha ng e is calculat ed from

∆ l = sL. kw [mm]

whe re∆ l = dimensional chang esL = bea ring w all thicknesskW = correction fa ctor for heat expansion

The correction fa ctor kW fo r the respective max. am bient t empera tures is show n in Diag ram 3.

The calcula t ed dimensiona l chang e must be ad ded to the operating bea ring play .

If i t is foreseeab le that polyamide frict ion b ea ring s are to b e used permane ntly under condit ionsw ith increased humidi ty or w a t er splashing , an ad di t iona l d imensiona l chan ge due t o mo istureab sorption must b e ta ken into account.

The e xpected dimensiona l cha ng e is calculat ed from

∆ l = sL. kF [mm]

whe re∆l = d imensio na l cha ng e

sL = bea ring w all thicknesskF = correction fa ctor for moisture ab sorpt ion

Diag ram 4 show s the correct ion f a c tor kF f o rthe respective m ax. humidity

The ca lcula ted d imensiona l cha ng e m ust beadd ed t o the opera t ing bear ing play.

The tw o values are de termined and ad ded for opera ting condit ions tha t req uire a correction d ueto temperat ure and moisture. The t ota l is the required a l low ance.

2.4 Design as slit bearing bush

For use in extreme mo isture a nd t empera tu-re cond i t ions , a b ea r ing b ush w ith a n ax ia lslit r u n nin g a t a n a n g l e o f 15° -30° t o t h esha f t ax is has proven to be t he b est so lut i-o n.

The slit a bsorb s the circumf erent ial expan sion

of the b earing bush so tha t a d iamet er chan-ge caused by the e f fects o f temperature or

moisture does not have to be considered

w hen calculat ing bea ring play. Only the w al l

thickness chang e ha s to be included , altho ugh

20 40 60 80 100

0,04

0,03

0,02

0,01

0

Bearing tempera ture in °C

C o r r e c t i o n f a c t o r k w

50 60 70 80 90 100

Relat ive humidity in %

0,06

0,05

0,04

0,03

0,02

0,01

0

C o r r e c t i o n f a c t o r k F

0 50 100 150 200 250 300 350

Bearing diamet er in mm

16

14

12

10

8

6

4

2

0

W i d t h o f s l i t i n m m

Diagram 3: Correction facto r kw

Diag ram 5: Width o f slit

Diagram 4: Correction f actor kF

1,5% of UL

1% of UL




th i s is minor compa red to t he change in d iameter

caused b y circumfe rentia l expa nsion.

In lubrica te d b ea ring s, th e sli t ca n a lso fu lf i l th ero le o f a lubr icant depot and co l lect abras ion

particles.

The w idth of the slit depend s on t he diame ter of t hebear ing and the requirements o f the opera t ingcond itions. We recom men d a slit a pprox. 1 – 1.5% ofthe circumference of the friction b ea ring .

2.5 Fixing

In pra ctice it ha s proved e xpedient t o press over-

d imensional f r i c t ion bear ings in to a bear ing

bo re. When i t is being set in , the b ea ring bush iscompressed by the amount o f the overs ize .

Theref ore t his oversize m ust be conside red a s an

a l lo w an ce to th e o p e ra t in g b e a r in g p l ay o n th e

in ternal d ia meter o f t he bush . Diag ram 6 show s

the required o versize.

As a result o f t empe rat ure increa ses, the stresses

in the bear ing become grea ter and there i s a

da ng er of relaxat ion w hen i t cools. This can lead to a situa t ion w here the f orce of pressure is no

long er ad eq uat e to keep the f r ict ion bea r ing in the bea r ing sea t under pressure . Because o f th i s

w e recommend an a dd it iona l sa feg uard fo r temperatures abo ve 50°C wi th a secur ing f o rm-f i t

element commo nly used in ma chine eng ineering .

3. Calculating dynamically loaded friction bearings

As opposed to frict ion b earings tha t a re only burdened b y a sta t ic norma l force, sta t ica l ly loa dedfrict ion b ea ring s are a lso subjected t o a ta ng ent ia l force. This lead s to a n increa se in t ransversestress in t he plastic and consequen tly to higher m at erial stress.

3.1 Continuous operation

Genera l ly the pv va lue (the prod uct o f t he a verag e surfa ce pressure and the a verag e runningspeed) is used as a chara cteristic value for th e dyna mic load bea ring ca pa city of f riction bea ring s.To calcula te t he dyna mic load bea ring capa city of rad ial bea ring s, it is necessa ry to de termine t hepvdurat ion value.

The averag e surface pressure fo r rad ial bea ring s is

whe re

F = bea ring loa d in Nd W = shaf t diameter in mmL = b ea rin g w id t h in m m

0,007

0,006

0,005

0,004

0,003

0,002

0,001

20 40 60 80 100 120 140 160 1800

Outer diamete r of the friction be aring

P r e s s - f i t o v e r s i z e p

e r m m D a

dw

SL

LD

Rad ial bea ring

[MPa]F

p =d w

. L

Diag ram 6: Req uired pre ss-fit oversize

Figure 5: Rad ial bea ring

15°- 30°

[mm]

[mm]




The a verag e running speed f or rad ial bearings is

d w .π. n

v = –––––––– [m /s]60000

whe red W = shaf t diamete r in mmn = speed in min -1

Hence pvdurat ion for d ynamic loading f or radia l bea rings w ithout lubricat ion is

r F i r d w. p . n i

pvdurat ion=e––––––e. e–––––––––– e [MPa . m/s]q d w

. L t q 60000 t

The ca lculat ed pvdura t ion value should be less or eq ua l to t he m a teria l-specif ic pv value sho w n inTa b le 4.

3.2 Intermittent operation

The d ynamic loa d bea ring capacity of thermo plastic frict ion b ea ring s is very much depend ent onthe hea t tha t builds up d uring operat ion. Accordingly, f r ict ion bea ring s in intermitt ent operat ionw i th a decreasing dut y cycle b ecome increa sing ly loa da ble . This is account ed for by using acorrection fa ctor fo r the rela tive d uty cycle (= ED).

Under the se cond itions, the follow ing applies to ra dial bea ring s in intermitten t opera tion

pvdurat ionpv

int= ––––––––-

f

whe ref = correction fa ctor for ED

The rela t ive duty cycle ED is def ined a s the ra t io o f t he loa d durat ion t to the to ta l cycle t ime Tinpercent.

For thermoplastic frict ion bearings, the tota l cycletime is de fined a s T= 60 min. The t ot a l of a ll individu a lloads during these 60 minutes forms the load dura-

tion.

This calculate d value can t hen b e used to d ete rmine t hecorrection fa ctor f f rom Diag ram 7. It should be no tedtha t every load dura t ion t , over and above 60 min .(rega rdless of w heth er this only ha ppens once), is to beevaluat ed a s cont inuous loa ding.

3.3 Determining sliding abrasion

It i s a very complex mat t er to de t ermine t he s lid ing a bras ion b eforeha nd in order t o d e terminethe expected life o f a friction b ea ring . Genera lly it is not possible to record t he externa l cond itionsad eq ua t e ly, or condit ions change d uring o pera t ion in a ma nner tha t cannot b e predetermined.How ever, it is possible t o ca lculate the expected sliding ab rasion sufficiently accurat ely to p rovidea rough est imate o f the l ife o f a bea r ing . Roughness, pressure and tempera t ure proport ions a reag greg at ed to form an e qua tion ba sed on simplif ied assumptions.

tED = . 100 [%]

T

0% 50% 100%

Relat ive d uty cycle ED

1,2

1,0

0,8

0,6

0,4

0,2

0 C o r r e c t i o n f a c t o r f

Diagram 7: Correction fa ctor f




Hence sliding ab rasion ∆ S is

r cF

cF–c0 i∆ S = 10pN (S0 + S1

. RV. + S2

. R2V ) . e1 - ––– + 400 d0 e. r2g [µm/km ]

q c0 t

whe reS0 = m ea su re d a nd e xp erie nce va lu eS1 = m ea su re d a nd e xp erie nce va lu eS2 = m ea su re d a nd e xp erie nce va lu ec0 = m ea su re d a nd e xp erie nce va lu ecF = slid in g su rf a ce t em pe ra t ure in ° CRV = a ve ra g e de pt h o f ro ug h ne ss in µmpN = m a xim um co m pre ssio n in MPa r2 = g ro ovin g d ire ct io n f a ct o rg = smo o t hing fa cto r

The g rooving d irection fa ctor r2 is only used in the e q uat ion if the sliding direction correspond s tothe direction o f t he processing g rooves of the meta l lic ma ting compo nent . This ta kes account o fthe inf luence of the d if ferent d egrees of roug hness during the rela t ive movement of t he met al licma ting compo nent in the same d irection and vertically to th e direction of the processing gro oves.

The smoo thing fa ctor g descr ibes the smoothing o f the meta llic mat ing component through theab rasion o f roug h tips an d/or the filling of roug hness troug hs w ith ab rad ed plastic ma terial.

Using an a pproxima tion eq uat ion the ma ximum compression pN is

16 FpN = –––– . ––––––––– [MPa ]

3p d w. L

whe reF = bea ring load in Nd W = shaf t diamete r in mmL = b ea ring w id th in mm

w here pN 6 (0,8 bis 1,0) ma y no t e xcee d j D (compressive stre ng th of th e respective pla stic).

The me a sured a nd e xperience values ca n b e seen in Ta ble 5, the g roo ving direction fa ctors inTab le 6. We d o not ha ve an y mea sured o r experience values for ma teria ls ot her th an tho se l istedbelow.

Material S0 S1 S2 c0 g

PA 6 0,267 0,134 0 120 0,7

PA 66 0,375 0,043 0 120 0,7

PA 12 0,102 0,270 0,076 110 0,7

POM-C 0,042 0,465 0,049 120 0,8

PE-UHMW 1,085 - 4,160 4,133 60 0,7

PET 0,020 0,201 - 0,007 110 0,8

PTFE 1,353 -19,43 117,5 200 0,6

Tab le 5: Measured an d e xperience values for ind ividua l plastics




Rv vertical to the direction of theprocessing grooves in µm PA POM-C PET PE-UHMW

> 0,5 1,0 0,9 0,8 0,80,5 – 1 0,9 0,6 0,6 0,4

1 – 2 0,8 0,3 0,4 0,2

2 – 4 0,8 0,2 0,3 —

4 – 6 0,8 0,2 0,3 —

3.4 Determining the service life of a bearing

As a rule, a plast ic frict ion b ea ring ha s rea ched th e end of i ts service li fe w hen t he b ea ring playha s rea ched an una ccepta bly h igh level . Bear ing play i s ma de up o f severa l f ac to rs. On the o ne

ha nd the re is so me de f o rma t io n due to the b e a r ing lo a d , a nd o n t he o the r ha nd the o pe ra t ingplay and the w ea r resul t ing f rom use must be considered. As these can only be a r ithm et ica l lyca lcula ted in ad vance and s ince the sl id ing ab ras ion ca lcula ted approximate ly a t 3 .3 is used tocalculate the service life, the service life itself should only be rega rded as a n a pproxima te value fora rough estimat e.

Unde r these prerequisites and in comb inat ion w ith the runn ing speed, th e expected service life His

r h 0 i

eDhper -Dh - eq 2 t

H = ––––––––––––––––––– . 103 [h]DS . v . 3,6

whe reDhpe r = permissible journal ho llow in mmDh = jo urna l ho llo w in mmh 0 = operat ing play in mmDS = w ea r ra t e in µmv = running speed in m/sec

To o bt a in a rough approxima t ion o f t he a ctua l serv ice li fe , it is accepta ble to leave the journa lhol low Dh o ut o f t he ca lculation , as in realistic cond ition s this is very sma ll a nd is of ten w ithin the

man ufacturing to lerance rang e.

Tab le 6: Groove direction f acto rs fo r plastics



Thermoplastic sliding pads



P l a s t i c s l i d i n g p a

d s

1. Thermoplastic sliding pads

In the same w ay tha t f r ict ion bearing bushes are used to arrang e the bea -

r in g s o f a sh a f t f o r ro t a t i o n a l an d u p a n d d o w n m o ve m e n t s, t h e sam e

plastics ca n of course be used fo r linear mo vements in the f orm of slidingpa ds. Basically a ll the plastics listed in the “ Friction bea ring s” chapt er a re

suita ble fo r use a s sliding pa ds. How ever, severa l are especia lly suita ble.

These w ill be described in the fo llow ing w ith their ad vant ag es.

1.1 Materials

Plas t ics tha t a re used as s lid ing pad s req uire g oo d sl id ing propert ies asw ell a s high stab i li ty an d elast ici ty an d creep resistan ce. These req uire-men ts a re fu lfilled especia lly w ell by Polyamide 6 ca st. The high stab ilitycompa red t o o the r thermo plastics a l low s higher load s. The g oo d elast i-city ensures tha t def ormat ion is reversed w hen t he ma teria l is subjected

to impact loa d pea ks. Assuming tha t t he load remains below the permis-sible limit , this ensures tha t permanent defo rmation is avoided t o a grea textent .

The o il-filled mo d ificat ion OILAMID is ava ila ble f or h igh ly stre ssedsliding pa ds. The o i l w hich is emb ed de d in th e mo lecular structureredu ces sliding f rict ion by a roun d 50% a nd a lso conside rab ly reducessliding a bra sion.

PET is be st suite d f or a pplicat ions w here a high level of mo isture is ex-pecte d. The m a te ria l has high me chan ica l sta bi l ity , creep resista nce,d imensiona l sta bi lity a nd go od s lid ing propert ies. Wat er ab sorpt ion i slow an d ha s virtua lly no eff ect on t he mecha nical or electrical properties.

How ever, PET is no t a s w ea r resista nt a s polya mide s. But PET-GL isa vai lab le as a m od if ied g rad e w ith a sol id lubrica nt . This ha s improvedsliding p roperties a nd much be tt er w ea r resista nce.

2. Design information

2.1 Friction heat

As opposed to f r ic t ion bear ings tha t opera te cont inuously a t h igh

speeds, most sl iding pad s and gu ide ra i ls usually wo rk under condit ionstha t m inimise t he evolut ion o f f r ic t ion hea t . The running speeds a rere la t ive ly s low and opera t ion i s more in termi t tent than cont inuous.Under t hese conditions, it is unlikely tha t f riction hea t b uilds up to a leveltha t could cause increased w ear or a b reakdow n in the compone nt.

Plastic sliding pads




d s

2.2 Pressure and running speed

As a rule, w hen d imensioning an d d esign ing sliding elements, the d esign eng ineers consider thepressure and speed rat io. If th e pressure an d speed ra tios are unfa vourab le, th e resulting frictionhe a t le a d s to e xce ss we a r a nd e v e n to a p re ma t ure bre a kdo w n o f the co mpo ne n t . Ho w e v e r,

experience in the d esign a nd o perat ion o f g uide pad s ha s show n tha t i t is ge neral ly unnecessaryto calcula te t he pressure and speed values due t o t he fa vourable opera ting cond it ions of slidingpad s. Instead of this, the fol low ing l imiting pressure values can b e used a s a ba sis fo r most g uiderail ap plications. The values apply at a sta nda rd te mpera ture o f 23° C.

2.3 Lubrication

Aga in the s ta tem ents rega rding dry running a nd t he use o f lubr icants f rom the “ Fr ic t ionbea ring s” chapt er apply. Basically it mu st b e said tha t installation lubrica tion considerab ly impro-ves the service life an d running beh aviour. The ma te ria ls th at ha ve been m od ified w ith lubricant ,such a s Oilamid, h a ve much long er service lives th a n a ll ot her pla stics.

2.4 Mounting

Polyamide s l id ing pads or guide ra i l sw i th a m echanica l sl id ing f unct ion a re

genera l ly mounted on s tee l construc-tions.

Count ersunk screw s or ma chine screw sca n be use d w itho u t a ny pro b le m f o ra pp l ica t io ns a t ro o m t e mpe ra ture a ndnormal climatic conditions (50% RH).For opera t ing condi t ions wi th h ighhumidi ty, w e recommend tha t you con-side r using PET/PET-GL.

I f a h igher ambient tempera ture i s

expected , t he approx .10 t imes h ig herlinea r expansion o f plastic com pa red t o stee l must b e considered. Firmly screw ed plastic rails cancorrug at e due to l inea r expan sion. To prevent t his from h appe ning, the moun ting po ints shouldbe less than 100mm apart . In the case of longer sl iding ra i ls , one single f ixed point screw isad v ised . The o ther screw s in ob long h oles should b e a ble to ab sorb t he t herma l expan sion .Instea d o f o blong ho les, the rails can a lso b e he ld in gro oves, T-slot s or similar. Cha ng es in leng thcaused by extreme amb ient cond it ions have no ef f ect on the f ixing or function.

For po lya mide sliding pa ds in high p erfo rma nce app licat ions such as telescopic boo ms on mo bilecra nes, we recomm end specia l nut s tha t a re pressed into hexag ona l holes on t he sliding pa nels. Bypressing the nut into the h exag ona l hole i t cannot fa ll out o r loosen. The b ott om of the slide pla teshould be a bsolutely flush.

PA PET Load Movement Lubrication

28 MPa 21 MPa int errupt ed int errupt ed perio d ic

14 MPa 10 MPa co nt inuo us int errupt ed perio d ic

3,5 MPa 2,5 MPa co nt inuo us co nt inuo us no ne

Figure 1: Example of thre ad ed inserts




d s

Under ful l torque, t he po lyam ide is held unde r pressure by th e th read ed insert a nd the insert sitson the steel support . For mo unting s such as this, pad thicknesses of 12 – 25mm a re ad eq uat e fo roptimum performance.

2.5 Applications and examples of shapesSlide a nd g uide pa ds in telescopic cran es, ga rba g e presses, car b od y presses, roa d a nd rail vehicles,timber processing ma chines and plants, packaging an d f illing plants, tran sport an d conveyor system s,chain g uides, et c.



Plastic castors



P l a s t i c c a s t o r s

1. Plastics as castor materials

Plas t ic wh eels and cas tors a re increasing ly used in plant s and ma ter ia l f low systems, replacingconventiona l ma terials.

This is beca use of ad vant ag es such as

• Cost-effe ctive m an ufa cturing• Very qu iet running• Hig h w ea r resista nce• Goo d vibrat ion a nd no ise da mping• Low w eight• Protection of the t racks• Corrosion resista nce

In a dd it ion t o t he so f t-e last ic wheels made f rom po lyure tha nes , hard e las t ic w heels and castorsma de f rom cast po lyam ide , POM and PET are po pular for h ighe r loa ds . How ever, compared to

convent iona l met a l w hee l a nd ca stor ma te ria ls, several plastic-specific prop erties must b e consi-dered w hen calcula t ing and dimensioning.

1.1 1.1 Materials

PA 6 G, PA 6/12 G a nd PA 12 G ha ve proved to be idea l mat erials. POM a nd PETcan a lso b e used.How ever, experience has show n th a t a l thoug h these ha ve a s imi la r load bea r ing capacity to thecast polyamides, they a re subject t o much more w ea r. The recovery capa city o f t hese ma teria ls islow er tha n tha t of polyamides. In dyna mic opera tion, f la t t ening tha t occurs under sta t ic loadingdo es not fo rm ba ck as easily as with po lya mide castors.

1.2 1.2 Differences between steel and plastic

Pla stic ha s a mu ch low er mod ulus of e last ici ty tha n stee l , w hich lead s to a rela t ively grea ter de -forma tion of plast ic w heels w hen the y are subjected to loads. But a t t he same t ime, this producesa l a rger pressure a rea a nd conseq uent ly a low er specif ic surface pressure , w hich pro t ects thetra ck. If th e load ing of the w heel rema ins w ithin th e permissible rang e, the d efo rmat ion q uicklydisa ppea rs due to the elastic properties of t he plastics.

In spite o f t he la rger pressure a rea , p las t ic w heels a re no t a s loa da ble as stee l w heels w i th thesame d imensions . One reason fo r th is is tha t p last ic wh eels can o nly wi thsta nd much sma llercompressive strain (compression ) in the cont a ct area , ano th er reason is th e tra nsverse stra in tha toccurs due t o t he very different deg rees of rigidity of t he castor a nd t rack ma terials. These hind erthe w heel from def orming a nd ha ve a neg at ive influence on the compressive stra in distribution inthe w heel.

1.3 Manufacture

There a re several produ ction processes tha t can b e used t o m an ufa cture plastic castors.If h ig h vo lumes o f w heels wi th smal l d imensions a re to be produced, in ject ion moulding i s asuita ble met hod . As a rule , fo r product ion-eng ineering rea sons , la rg er d imensions can only beproduced b y injection moulding a s recessed and ribb ed prof i le castors. It must a lso b e no ted tha tthe se on ly ha ve half the load bea ring capa city of a solid castor w ith the sam e dimensions. It is a lsoa very com plex procedure t o calcula te a castor such a s th is compa red t o a solid ca stor, and rollingspeeds of mo re tha n 3m/s are not recommend ed beca use o f prod uction-relat ed e ccent ricity.An econo mic a nd t echnical a l terna tive to injection mo ulding is to ma chine semi-f inished p ro-ducts. In the small dimensiona l rang e up to Ø 100mm, the casto rs are ma nufa ctured on a uto ma ticlath es from rod s. Sizes ab ove th is are pro duced o n CNC lat hes from b lanks.

Ano the r alterna tive is th e centrifug al moulding process. In th is process, th e out er con to urs of thecastor a re moulded to size a nd t hen only the bea r ing sea t and ax is ho les a re machined t o t he re-q uired f inished size. This allow s large q ua nt ities of la rger dimensions to be ma nuf actu red econo -mically.

Plastic castors




With t his process, running truth s are a chieved t ha t allow speed s of up to 5 m/s.

1.4 Castor design

In a dd i t ion t o t he fo ur ba sic cas tor bo dy shapes , casto rs d i f fer ma inly in th e type a nd d esign o f

th eir bea ring s. Like rope pulleys, solid castors can a lso b e f i t ted w ith frict ion bea ring s. A prere-q uisi te is that the ma teria l-specif ic ma x. load ing pa ramet ers are no t exceeded. How to calcula tefrict ion b earings and th e signif icant fa ctors for sa fe operat ion o f th e bea ring are conta ined in thechap te r on »Friction b ea rings«. If it is no t po ssible to use a f riction be a ring b ecau se the loa d is to ohigh or beca use of o the r facto rs, the use of a ntifriction be arings is recomm end ed.The cha pt er o n »To lera nce s«, sec-t ion 2 .5 .2 dea ls wi th the mater ia l-re la ted design o f bear ing sea ts indeta i l .Compression-set anti frict ion bea-r ings used a t tempera tures above50° C ca n loo sen. This ca n b e cou n-tera cted b y design mea sures such as

pressing the bear ing in to a s tee lf lange sleeve screw ed t o t he bo dy ofthe castor. Alternatively we recom-mend the use o f our Ca laumid-Femateria ls (PA with a metal core),w h ich co mbine s the a dv a n ta g e s o fplast ic as a castor ma teria l and steelas a bea ring seat mat eria l . Because of its form a nd f rict iona l connection of the steel core w ith t heplast ic, this ma teria l is a lso recomm ende d fo r applicat ions w here driving to rque h a s to be t rans-ferred.For ca sto r diam ete rs > 250 mm, a lined castor d esign is a dvan ta g eou s. The p lastic lining is fixed tothe meta l l ic core o f the cas tor through shr inkage . Deta i l s o f th is design a l terna t ive wi l l be

described in a sepa rat e section.

2. Calculation

When calculat ing plastic casto rs, several impo rta nt points must b e remem bered . The ma terial ha svisco-elast ic propert ies, w hich be come visible throug h de crease in rigidi ty as the loa d d urat ion

increases. The result o f t his is tha t w hen t he cont act a rea o f t he sta t ic wh eel is cont inuously loa -ded , it b ecomes larg er the long er this load continues. How ever, as a rule becau se of t he ma terials’elast ic properties, they a re q uickly able to return to their original shape w hen t hey be gin rol ling .Hence , no neg a t ive b eha v iour i s to be expected during o pera t ion . But i f the permissible y ie ldstress o f the ma ter ia l i s exceeded the mat er ia l can »f low «and lead to permanent de fo rmat ion .This causes increa sed start -up fo rces w hen t he casto r or w heel is resta rted an d eccent ricity in thero l ling mo vement . High am bient t empera t ures an d, especia l ly for po lyam ides, h igh humidi typromot e t h is beha v iour, a s they reduce t he ma ximum y ie ld st ress. An except ion to th is a re th ePA 12 G po lya mides, as they ha ve less ten den cy to ab sorb w at er.It should a lso b e not ed t ha t because o f the ma ter ia l ’s good da mping propert ies, the b ody o f thecasto r can hea t up as a result o f h igh running speeds or o t her loading f a c tors. In ex treme cases,temperat ures can o ccur tha t cause the plast ic w heel to malfunction. How ever, if t he load s remain

w ithin the permissible limits, pla stic casto rs and w heels w ill opera te saf ely and reliably.

2.1 Calculation basics

It w ould a ppea r practical to a pply the Hertzia n rela tionships w hen calculat ing castors. But plasticw heels do no t f ulfil all the conditions for t his a pproa ch. For example, the re is no linea r conn ection

Figure 1: Basic castor sha pes




bet w een stress an d expan sion, and becau se of the elasticity of t he ma terial, shea r stresses occur inthe conta ct a rea w hi le th e w heel is ro l ling . Nevertheless, it i s possible to ma ke an ad eq ua t e lyprecise calcula tion o n t he b asis of Hertz’ theo ry. The compression pa rame ter p’ is determined w iththe fo l low ing ca lcula t ions . This para met er i s genera l ly ca lcula t ed w i th short-t ime m od ulus o felast icity det ermined a t roo m tem perature a nd t herefore do es not ref lect t he a ctual compression

in the cont act a rea . Because o f t h is, the de t ermined va lues a re o nly expressive in combina t ionw ith Diag rams 1 to 4.The calcula t ed values are usua lly ra th er hig her tha n tho se th at a ctua l ly occur during ope rat ionan d t here fore conta in a cer ta in deg ree o f sa f e ty . St i ll , castors or w heels can ma l funct ion a s it i snot possible to consider a l l the unknown parameters tha t can occur during opera t ion to anad eq uat e extent in the calcula t ion.For castors w ith frict ion b ea ring s, the load l imit of the frict ion b ea ring is decisive. As a rule, thefull load b ea ring ca pa city of t he running surface ca nno t be ut ilised, a s the loa d limit of t he frictionbe a ring is reache d b ef oreh a nd (see cha pt er »Friction be a ring s«).

2.2 Cylindrical castor/flat track

Unde r lo a d , a p ro je c te d co n ta c t a re a i s f o rme d w ith l e ng th 2a a nd w id th B , w i th co mpre ssio ndistribute d o ver the a rea in a hemiellipsoida l form. Not icea ble is tha t t he stress increases a t t heed g es of t he ca stor. This stress increa se is g ene rat ed b y shea r stresses th a t o ccur across th e runningdirection . These ha ve the ir origins in t he ela stic be ha viour o f t he ca stor ma te rial. The stress increa -ses become la rger t he g rea ter the d i f ferences in r ig id ity be t w een t he t ra ck and the cas tor ma te-rials. As stress increa se in a ca stor ma de f rom ha rd-elastic pla stic is q uite sma ll a nd ca n th eref orebe igno red for opera t ing purposes an d a s the shear s t resses canno t be ca lcula t ed w i th Hertz ’the ory, these are not considered .

Assuming t ha t th e tra ck ma terial has a much hig her mod ulus of elasticity than t he castor ma teriala nd t ha t t he ra dii in the principa l curvat ure level (PCL) 2 are infinite , the com pression pa ram et erp’ is

where :F = w hee l lo ad in N

r11 = castor rad ius in mm f rom PCL 1B = w h ee l w id t h in mm

f w = mater ia l f ac tor

PA 6 G = 25.4

PA 6 = 38

POM = 33.7

If the mod ul i o f e las t ici ty o f the cas tor and t rack mater ia ls a re know n, the fo l low ing eq ua t ionscan be used:

a nd

1 1 1 - v21 1 - v2

2–– = –– –––– + –––––

Ee 2 E1 E2

p ’ = f w F

r11. B

[MPa]

p’ =F . Ee

2 . p . r11. B

[MPa]

r11

F

2 a

p ’

B

Principal curvatu re level1 2




For ident ical tra ck an d ca stor ma terials Ee is

EEe = ––––––

1 - v2

whe re

F = w h e el lo a d in NEe = replacement module in MPar11 = castor rad ius in mm f rom PCL 1B = w h e el w i d t h in mmE1 = mod ulus of e lasticity of t he castor bo dy in MPav1 = tra nsversal contra ction coefficient of the castor bo dy from Ta ble 1E2 = mod ulus of e lasticity of t he tra ck ma terial in MPav2 = tra nsversal contra ction coefficient of the tra ck ma terial from Tab le 1

Tab le 1: Transversal con tra ction coeff icients f or va rious ma terials

PA 6 Ca st iro nPA 6 G St eel w it hPOM Ferrit ic a ppro x. Austenit ic GG GG GG GGG 38 Aluminium Tit a n iumPET st eels 12% Cr steels 20 30 40 to 72 a llo ys a llo ys

Tra nsversa l con - 0,4 up 0,25 0,24 0,24 0,28 0,23traction coeffi- to 0,3 0,3 0,3 up t o up to up t o up t o 0,33 up t ocient µat 20° C 0,44 0,26 0,26 0,26 0,29 0,38

The ha lf conta ct area length req uired to estimate flatt ening is calculat ed f rom

8

.

F

.

r11a = ––––––––– [mm]p . Ee. B

whe reF = w h e el lo a d in NEe = replacement module in MPar11 = castor rad ius in mm f rom PCL 1B = w h e el w i d t h in mm

2.3 Cylindrical castor/curved track

Also in this system a projected contacta rea i s formed w ith length 2a and w idthB, w ith compression distributed over thea rea in a h emiellipsoida l form. The p re-viously described stress increases alsoform in the edg e zones.The ca lculat ion is ca rried out in the samew a y as for th e “ cylindrica l ca stor/f la tt ra ck” f rom sect ion 2 .2 . How ever, be-cause of the second radius in PCL 1, areplacement radius re is fo rmed from t herad ii r11 a n d r21. This is used in th e eq ua -

t ion corresponding to re la t ionships o fthe mod ul i o f e las t ic ity t o ca lcula te t hecompression pa ramet er.If t he casto r runs on a curved tra ck the repla cement ra dius is

F

p ’

r11

r21

2 a

B





r11. r21re = ––––––– [mm]

r11 + r21

For castors running on a curved tra ck the replacemen t ra dius is

r11. r21re = ––––––– [mm]

r11 - r21

whe rer11 = castor radius in mm from PCL 1r21 = track radius in mm from PCL 1

The replacemen t rad ius re is also used in the eq uat ion to calculate ha lf the cont act a rea length a .

2.4 Curved castor/ flat track castor system

The phe no men on d escribe d in section 2.2, w here stress increa ses a t t he ed g es, can b e reducedw ith design chang es of the sha pe of t he w heel . If th e tra ck is furthe rmore sl igh tly curved a crossth e rol l ing direction, o nly minor stress increases are o bserved. It ha s proven practica l to use the

diam et er of th e w heel as the rad ius of t he curva ture. This mea sure also coun tera cts the e volutionof excess edg e pressure th at could arise f rom a lign ment errors during a ssemb ly.A casto r w ith curves in PCL 1 a nd 2 fo rms a n el liptica l cont a ct area w ith a xes 2a a nd 2b a crossw hich the com pression is distribut ed in the fo rm of an el lipsoid. The semi axis of th e el l iptica lcontact a rea are calcula t ed from

1 1a = s . 3 3 . F . re

. ––– [mm] a nd b = l . 3 3 . F . re. ––– [mm]

Ee Ee

a nd

r11. r12re = ––––––– [mm ]

r11 + r12

whe reF = w h e el lo a d in NEe = replacement module in MPas = Hertz correction value from Tab le 2re = substitute radiusl = Hertz correction value from Tab le 2

The repla cemen t mo du le is de te rmined a s de scribed in section 2.2.To d et ermine t he Hertz co rrection values s a nd l the va lue cos t must be dete rmined ma thma tica lly.

r 1 1 ie––- - ------eq r11 r12 t

cos t = ––––––––––––r 1 1 ie–– - + ------eq r11 r12 t

whe rer11 = castor rad ius in mm f rom PCL 1r12 = Rcasto r rad ius in mm fro m PCL 2

The Hertz correction values in rela t ion t o cos t can b e t aken f rom Tab le 2. In termed ia te va luesmust b e interpola ted .

Tab le 2: Hertz correction va lues in rela tion to cos t

cos t 1 0,985 0,940 0,866 0,766 0,643 0,500 0,342 0,174 0

s ∞ 6,612 3,778 2,731 2,136 1,754 1,486 1,284 1,128 1

l 0 0,319 0,408 0,493 0,567 0,641 0,717 0,802 0,893 1

w ∞ 2,80 2,30 1,98 1,74 1,55 1,39 1,25 1,12 1

r11

F

B

2 a

p ’ r12

2 b





With these calculated values the com pression para met er can be d ete rmined a s fo llow s:

3 . Fp’ = ––––––––––––––––– [M Pa ]

2 . p . a . b

whe reF = w heel lo a d in Na = se m i a xis o f t h e co n t a ct a r ea l on g it u d in a lly t o t he ru nn in g d ire ct io nb = se m i a xis o f t h e co n t a ct a r ea t r a n sve rse ly t o t h e ru nn in g d ire ct io n

2.5 Curved castor/curved track castor system

Both t he shape of the cont act a rea a nd t he calcula t ion correspond to section 2.3. How ever, w henthe replacement radius r and the value fo r cos t are b eing calcula t ed, i t should be considered t hatth e t rack also ha s curvat ure ra dii in PCL 1 and 2.Conseq uent ly the replacement ra dius fo r casto rs tha t roll on a curved tra ck is

1 1 1 1 1––– = –––– + –––– + –––– + –––– [mm ]re r11 r12 r21 r22

and for castors tha t rol lin a curved tra ck

1 1 1 1 1––– = –––– + –––– + –––– + –––– [mm ]re r11 r12 -r21 -r22

whe rer11 = castor rad ius in mm f rom PCL 1r12 = castor rad ius in mm f rom PCL 2r21 = tra ck rad ius in mm f rom PCL 1

r22 = tra ck rad ius in mm f rom PCL 2

When determining cos t i t should bere me mbe re d t ha t the v a lue sho u ld b e co n-s ide re d inde pe nde n t l y o f whe the r thecastor runs on o r in a tra ck. Therefo re in theeq ua tion a posit ive value is a lw a ys used forthe ra dii.

r 1 1 i r 1 1 ie–– - –– e + e––- –– eq r11 r12 t q r21 r22 t

cos t = –––––––––––––––––––––––––––––r 1 1 i r 1 1 i

e–– + ––e + e–– + ––eq r11 r12 t q r21 r22 t

To ca lcula t e th e semi ax is a a nd b an d t he compression para met er the m etho d d escr ibed insection 2.4 can be a pplied.

2.6 Cylindrical plastic castor lining

2.6.1 Calculation

Castor l inings can o nly be calcula te d a ccord ing t o t he eq ua tions in sections 2.2 to 2 .5 if specif icra t i o s be tw e e n the ha lf co n ta c t a re a l e ng th a , the w he e l w id th B a nd the he ig h t o f t he l in ing hare fulfilled.

The ra t ios h /a ≥ 5 a nd B/a ≥ 10 must b e f ulfilled as a condition. As soo n a s these limiting va lues arenot met, the evolving contact a rea is reduced despite t he same load and oute r w heel dimensions.The result is tha t the compression of the conta ct a rea increases and becomes g reat er, the sma llerth e l ining th ickness. In spite o f t his, i t is possible t o d et ermine t he com pression ra t ios ap proxi-mately.

F

r11

r21

2 a

B

p ’

2 b

r12

r22





The ha lf conta ct a rea length a becomes

F E’1 . h2

+ E’2 . h 1a = 3 1,5 . re. –––. ––––––––––––––––––––– [mm]

B E’1 . E’2

For castor lining s tha t run on a f la t t rackr e = r1. For castor l inings that run on orin a curved tra ck, the replacement rad iusr e is de te rmined a s de scribe d in section2.3.

The compression pa ramet er the n be comes

9 1 r F i2

E’1 . E’2p ’ = 3 ––– . ––– . e – e . –––– –––––––––––––– [MPa ]32 r

e

q B t E’1. h

2+ E’

2. h

1

whe reF = w heel lo a d in N re = replacement rad ius in mmE1 = ca lcula t ion module o f w heel mater ia l in MPa h 1 = casto r lining th ickness in mmE2 = ca lcula t ion module o f t rack mater ia l in MPa h 2 = tra ck th ickness in mm

B = w heel w idth in mmThe ca lcula t ion mo dul i o f the ma ter ia ls must be d e termined t aking a ccount o f the t ran sversa lcontra ction coeff icients.

E1 (1 - v1)2 E2 (1 - v1)

2

E’1 = –––––––. –––––––––– und E’2 = –––––––. –––––––––– [MPa ]1 - v2

1 1 - 2v1 1 - v22 1 - 2v2

whe reE1= mod ulus of e lasticity of the ca sto r mat erial in MPav1 = tra nsversa l cont raction coeff icient of the castor ma terial from Tab le 1E2 = mod ulus of e lasticity of t he tra ck ma terial in MPav2 = tra nsversa l cont raction coeff icient of the tra ck ma terial from Tab le 1

2.6.2 Design and assembly information

The shape o f th e plast ic castor l inings and th e met a l lic core is g enera l ly depen den t o n the t ypeo f l o a d tha t the ca s to r w i l l besubjected to . For cas tors wi th alo w lo a d w he re no a xia l she a r i sexpected a nd w here the d iamet eris < 400mm , it is possible t o ch oo sea core shape w ith n o side support .The ope ra t ing tem pera t ures ma yno t e xceed 40° C. If i t is expecte dtha t a x i a l f o rce s ma y a f f e c t thecastor , tha t the l in ing wi l l besubjected to high pressures ortha t o pe ra t ing t e mpe ra ture s w illexceed 40 °C for short or longperiods, the l inings must be se-cure d a g a inst s lid ing do w n by as ide co lla r on t he core or w ith af lan g e. The sam e a pplies for cas-tor diameters ≥ 400mm.

h1

F

2a

p’

r11

B

B a r e s n a p - b a c k s i z e

A x i a l p l a y

40 60 80 100

Opera t ing tempera ture

°C

Aufschrumpfuntermaß in Abhängigkeit zur Betriebstemperatur

0,25

0,45

0,65

0,85

%

0,25

0,45

0,65

0,85

%

0,05 0,05

Diagram 1: Bare snap-back size and a xial play in relationto opera t ing tempera ture

Principa l curvat ure level1 2




No specia l deman ds a re placed on themeta l core in the a rea of support for thel in ing in reg ard t o surfa ce qua l ity an ddimensional stabi l i ty . A cleanly ma-chined surface and a diamete r toleran ce

of d ± 0.05mm are adeq ua te . Grooves inthe axia l direction (e.g . knurls withgroo ves para l le l to t he a x is and b rokentips) are permissible. Approxima te ly 1.0to 1.5% of d ha s proven to b e a suita bleheight fo r the plastic lining .The lining is g enera lly fixed to th e me ta lcore by hea t ing i t and then shr inking iton to the co ld core . The l in ing ca n b ehea ted e i ther wi th c i rcula t ing hot a i r(a pprox. 120 to 140°C) or in a w a ter b at h(ap pro x. 90 to 100° C). The lining is

hea t ed to a n extent t ha t it can be eas ilydra w n o n t o the co ld co re w ith a g a p be tw e e n the co re a nd the lin ing a ll the w a y a ro und . Th isprocess should b e carr ied out q uickly so t ha t the l in ing d oes not become co ld bef ore i t s it sproperly on t he core. Rap id or uneven cooling should be a voided a t a ll costs, as othe rw ise stressesw i ll form in the l in ing . The b are snap-ba ck s ize f or ma nufa ctur ing the l in ing d epend s on th eo pe ra t ing t e mpe ra ture a nd t he d i a me te r o f the me t a l co re . D ia g ra m 1 sho w s the pro po rt io na lba re size in relat ion to t he diam ete r of the me ta l core for casto rs w ith a diam ete r of > 250mm. Forcasto rs w ith a securing collar/f lang e a sl igh t a xia l play must be considered to ab sorb the chang esin widt h resulting from t herma l expansion. The propo rtiona l axial play in relat ion to t he w idth o fthe lining can also be seen in Diag ram 1.

2.7 Maximum permissible compression parameters

Diag rams 2 to 5 show the l imit load s of castor ma teria ls fo r various temperat ures an d in rela t ionto th e rolling speed. The results for compression pa rame ters ga ined from the calculations ha ve tobe com pa red w ith th ese limits and ma y not exceed the ma ximum va lues. The curves in relation t othe rolling speed reflect the load limits in cont inuous use. In intermitte nt o perat ion, higher valuesmay b e permitte d. Unallow ab le high load s must b e a voided w hen th e castor is sta t ionary, as thesecould cause irreversible def orma tion (flat ten ing) of t he conta ct area .

L o

a d l i m i t p ’ m a x

0 1 2

20

10

30

43 5

40

50

60

70

80

20°C

50°C

75°C

100°C

m/s

90

Loa d limit for ba ll bearing solid castors made f rom PA 6 G

Rolling speed

MP a

L o a d l i m i t p ’ m a x

0 1 2

20

10

30

43 5

40

50

60

70

80

m/s

90

Load limit for ball bearing solid castors made from POM

Rolling speed

MPa

20°C

50°C

75°C

100°C

Dia g ra m 2 Dia g ra m 3

h

ø D

ø d

a




3. Estimating the elastic deformationof the castor body

Often t he function o f castors and w heels is depende nt o n the d eforma tion of t he running surface(flat te ning) wh ile th e w heel or ca stor is stat iona ry. This is de te rmined immedia te ly a ft er the loa dha s taken e f f ect w ith t he mo dulus o f e las t ic ity o f the ma ter ia l . How ever, because o f t he v isco-

elast ic behaviour of the plast ic, the t ime-rela t ed defo rmation b ehaviour must be determined w ithth e pa rt-specif ic creep mo dulus. The creep mo dulus is dete rmined b y carrying ou t creep expe-riment s w ith casto rs an d can b e seen in Diag rams 6 an d 7. On the ba sis of t he values det erminedin experiments, the t ime-rela t ed f la t tening can only be estimat ed w ith the fol low ing eq uat ions. Iti s v ir tua l ly impossible to m ake an e xact ca lcula t ion due to the o f t en unknow n opera t ing pa ra-met ers an d th e special properties of t he plastic. But the values ob ta ined from th e eq ua tions allow the f la t te ning to be det ermined approximat ely enough to assess the f unctioning ef f iciency.The f ollow ing is used t o e stimat e t he cylindrica l ca stor/cylindrical tra ck

1,5 . w . FoA = –––––––––––––– [m m]

Ee. a

a nd t he cylindrical ca stor/fla t t rackF r r 2 . r11 i i

oA = --––––––––––––– . e2 . ln e–––––– e+ 0,386e [mm]p . Ee

. B q q a t t

whe re


20

20

40

60

40

80

100

60 80 100°C

Loa d limit for PA 6 G castors wit h stat ic load ing

MP a

Ambient temperature vu


20

20

40

60

40

80

100

60 80 100°C

Load limit for POM castors with static loading

MP a

Ambient temperature vu

Diag ram 4

Diag ram 5



F = w h e el lo a d in NW = Hertz correction value f rom Tab le 2Ee = mod ulus of elasticity or creep mo dulus in MPaa = semi axis o f the contact a rea longi tudina l to t he running direct ionB = w h e el w i d t h in mm

r11 = castor rad ius in mm f rom PCL 1

As in ca stor syste ms w ith curvat ure ra dii qu ite con side rab le shea r stresses occur in t he PCL 2, it isno t po ssible to a na lytically estimat e t he syste ms w ith curva ture ra dii in t he PCL 2. These can o nlybe det ermined num erically w ith a three-dimensiona l FE mod el.

75


C r e e p m o d u l u s

Loa d t ime

10-4

10-3

10-2

10-1

10-0

101

102

103

h

Creep mod ulus of PA 6 G a t 20 °C

500

1000

1500

2000

2500

3000

MP a

C r e e p m o d u

l u s

Loa d t ime

10-4

10-3

10-2

10-1

10-0

101

102

103

Creep modu lus of POM a t 20 °C

500

1000

1500

2000

2500

3000

MP a

h

Diag ram 6

Diag ram 7



Plastic sheaves



P l a s t i c s h e a v e s

Plastic sheaves

1. Use of PA 6 G as a sheave material

Ste el w ire ropes are import a nt a nd h ighly stressed m achine element s in conveying t echno logy. Inma ny cases, la rge plan ts depen ds on th eir functioning not only for ef f iciency but a lso safe ty . As

opposed to other ma chine elements, they must b e replaced bef ore they are completely dama ged .

The surfa ce pressure tha t o ccurs a t the po int o f cont act b e tw een t he sheave an d t he rope i sdecisive fo r the service life a nd loa da bility of ro pes tha t run o ver shea ves. Shea ve mat erials with alow mod ulus of elasticity lea d t o low surfa ce pressures and con seq uent ly to a longe r service life ofthe rope. For th is reason, th ermoplastics are used t o ma nufa cture shea ves.

The plasticvs need to off er the fo llow ing prope rties:

• Rop e con serving e lasticity• Adeq uat e compression fa t igue strength• High w ea r resista nce

• Adeq uat e toug hness, a lso a t low t emperatures• Resistance to lubricants• High resista nce to w eat hering ef fects

Experience ha s show n t ha t cas t po lyamide (PA 6 G) fu lf i ls these requirements more tha n a de-q ua te ly. Oth er pla stics such as PE-UHMW or PVC as sho ck-resista nt mo dif ica tio ns are o nly used inspecia l cases due to their low deg ree of loa da bility a nd low er w ear resista nce. Because o f t his, w ew ill only dea l w ith PA 6 G a s a shea ve mat erial in the f ollow ing.

1.1 Advantages of sheaves made from PA 6 G

1.1.1 Low rope wearRopes tha t run o ver shea ves ma de f rom met a l lic ma ter ia ls a re subject to h igh s t ress due to thesurface pressure tha t o ccurs be t w een t he rope a nd t he g roove . When t he rope ro l ls over thesheave, only the ou ter strand s lie on the g roove. The result o f t his is w ea r in th e fo rm of individua lstrand s brea king or, more serious, rope b reaka ge .

Shea ves ma de from PA 6 G prevent t his due to their elast ic beha viour. The pressure be tw een therope a nd t he rol ler in the comb inat ion steel rope/polyam ide rol ler is a round 1:10 compa red t osteel rope /steel roller. This ca n b e a tt ribut ed to th e visco-elastic beha viour o f p olyam ide. It is no tjust t he o uter s t rands tha t l ie in the g roove , but a lmost t he w hole projected s t rand w idth . Thisreduces surface pressure betw een t he rope and the roller and considerab ly extend s the l ife o f t herope.

1.1.2 Weight reduction

Polyam ides a re a round seven t imes ligh ter tha n stee l . Because o f t he w eight a dvant ag e , a con-siderable w eight reduct ion can be achieved b y using po lyamide sheaves w ith a s imi la r loa dbea ring capa city . A mob ile crane w ith up t o 18 polyam ide sheaves can save approx. 1,000kg a ndthus reduce the a xle loa d. The l igh ter sheave w eight a lso ha s a posit ive ef f ect on t he crane b oo man d considera bly ea ses the ha ndling an d a ssembly of t he sheaves.




1.1.3 Damping

The g oo d d am ping properties of PA 6 G reduce vibration t ha t m eta l lic shea ves tran sfer from therope via t he sheave to the sha ft a nd b ea ring s. This conserves the ro pe, sha ft a nd b ea ring s an d a lsoreduces running noise.

1.2 Lubricating the rope

The use of viscous and a dh esive rope lubrica nt s can cause th e rope t o stick to th e shea ve groo ve.In combina t ion wi th a dusty env ironment or d i r t par t ic les tha t a re in troduced to the sheavesystem, th is forms an a bras ive paste tha t can cause increased w ear o n the rope a nd t he sheave .Therefo re w e recommend tha t t he rope is lubricat ed w ith a low viscous corrosion pro tection o i l,w hich keeps the ro pe a nd t he sheave relat ively clea n.

1.3 Wear on sheaves made from PA 6 G

Essent ially, w ea r is caused o n po lyamide shea ves th roug h excess mechan ica l stre ss or w hee l slip,

w hereby t he shea ve groo ve is the mo st stressed p oint. The shea ve groo ve is subjected to pulsat ingstresses as the rope rolls over it a nd it b ecomes w arm a t hig h speeds.

Basically, w ea r on idler shea ves or sheaves tha t run o ver a t au t rop e is less than on driven shea ves.If strand ed rope s are used, the individua l stra nds ca n press into t he ba se of t he g roove in high lystressed applicat ions. For highly stressed, non-sl ipping sheaves in combination with an openstrand ed rope, the circumference of the groo ve base must no t b e an integ ral multiple of the w irestran d. Thus, l ike the combing tee t h o f a cog w heel , it i s prevented tha t t he same po ints o f t heg roove ba se are constant ly in cont act w ith a ro pe summit or valley. When closed ro pes are used incombina t ion w ith lubr icants , p its can form, w hich a re proba bly caused in the same w ay a s p i tsform w ith gea r w heels. As a rule, under norma l environmenta l condit ions and w hen t he l imit loa dvalues are not exceeded, one can expect g roove base w ear of ≤ 0.1µm/km .

2. Construction Design information

2.1 Sheave groove profile

The rad ius of the sheave g roove should be a pprox. 5 – 10% larger t ha n ha lf the d iamet er of t herope. This ensures tha t rope t olerances are ad eq ua tely con sidered a nd t ha t t he rope sits w ell inthe g roove.The shea ve gro ove d ept h h is given in DIN 15061 part 1 for stee l shea ves as at least h min = da2.We recommend a sheave groo ve depth of h ≥ 1.5d fo r polyamide sheaves.The V a ng le b is depen den t o n the la tera l f leet a ng le (ma x. permissible f leet a ng le in the gro ovedirection = 4.0°).

The fo llow ing g roove a ng les in comb inat ionw ith the f lee t a ngle have s tood the test :

Fle e t a ng le 0° - 2. 5° c b = 45°Fleet a ng le >2.5° - 4.0° c b = 52°

A groo ve angle of < 45° should be a voided.DIN 15061 pa rt 1 recomm end s the dimen sion s inTa ble 1 as guiding values for shea ve gro ove pro files.

As a guiding value for the diameter of the ropegroo ve base of rope disks mad e from castpolyamide, w e recommend :

D1 = 22 · d 1 [mm]

Groove angle b

Rounded

Rope ø d 1

mm

h

Groove rad ius rD1




Ø d1 r1 h m Ø d1 r1 h m Ø d1 r1 h m

3 1,6 8 2 21 11 35 7 39 21 60 11

4 2,2 10 2 22 12 35 7 40 21 60 11

5 2,7 12,5 2 23 12,5 35 7 41 23 60 11

6 3,2 12,5 3 24 13 37,5 8 42 23 65 11

7 3,7 15 4 25 13,5 40 8 43 23 65 11

8 4,2 15 4 26 14 40 8 44 24 65 12,5

9 4,8 17,5 4,5 27 15 40 8 45 24 65 12,5

10 5,3 17,5 4,5 28 15 40 8 46 25 67,5 12,5

11 6,0 20 5 29 16 45 8 47 25 70 12,5

12 6,5 20 5 30 16 45 8 48 26 70 12,5

13 7,0 22,5 5 31 17 45 8 49 26 72,5 12,5

14 7,5 25 6 32 17 45 8 50 27 72,5 12,5

15 8,0 25 6 33 18 50 10 52 28 75 12,5

16 8,5 27,5 6 34 19 50 10 54 29 77,5 12,5

17 9,0 30 6 35 19 55 10 56 30 80 12,5

18 9,5 30 6 36 19 55 10 58 31 82,5 12,5

19 10,0 32,5 7 37 20 55 11 60 32 85 12,5

20 10,5 35 7 38 20 55 11 – – – –

2.2 Bearings

Due to the g oo d sliding properties of PA 6 G, wh en shea ves a re not subjected t o und ue stress, fric-

t ion b ea ring s can be used. Decisive is the pv l imiting value. If high deg rees of w ea r are e xpectedon t he bea r ing w ith a n in tact sheave groove , the use o f a replaceab le bea r ing b ush can preventthe shea ve ha ving t o be replaced premat urely.

For highly stressed shea ves, w hose ma ximum loa d values are ab ove th ose for a f rict ion b ea ring ,w e recom mend th e insta llat ion of a nt i-friction be aring s. These can b e mou nte d by pressing th eminto a bea ring sea t prod uced according to the d imensions in Diag rams 1 a nd 2. If a xia l loa ds areexpected on t he a nti-frict ion b ea ring s, w e recommen d t hat the b earing is secured a ga inst f a l lingout by securing eleme nt s commo nly used in ma chine en g ineering, such a s circl ips accord ing t oDIN 472.

The fo llow ing d iag ram show s several possible shea ve designs.

1 2 3 4 5

Design w ith bea ring seat for ant ifriction bea rings Design w ith friction bea rings

Tab le 1: Guiding va lues for rope gro ove prof iles in mm a ccording to DIN 15061 Part 1




When calculat ing a nd d imensioning th e be arings, especially friction b ea ring s, at ten tion should b epaid t hat the b earing load for idler sheaves corresponds to the rope tension, but for f ixed sheavesth e an gle of conta ct forms a fo rce eq ua l to tw ice the ca ble tension at 180°. Section 3 »Calculating

sheaves«provides mo re informa tion on this subject.

0,0

0,1

1,0

0,9

0,8

0,7

0,6

0,5

0,4

0,3

0,2

0 10 30 50 100 150 200 225175125754020

0,007

0,006

0,005

0,004

0,003

0,002

0,001

0 60 100 160 200 250180140804020 120

Interna l diamet er of bearing (mm)

Outer diameter of t he ant ifriction bea ring (mm)

O p e r a t i n g b e a r i n g p l a y i n

%

B o r e s e t t i n g s i z e p e r m m o u t e r d i a m e t e r

Diagram 1: Recommende d bo re sett ing size for a ntifriction bea ring seat s

Diagram 2: Recommende d opera ting be aring play for friction bea ring s




3. Calculating rope pulleys sheavesFor th e calcula t ion o f sheaves, dist inctions must be m ad e reg arding the load case, the rope usedand the type o f opera t ion .

A distinction is ma de b etw een

• Point load ing on t he sheave • Circumfe rential loa ding o n th e shea ve(t he shea ve runs o n a ta ut ro pe) (ro pe encircles t he shea ve)

• The t ype o f ro pe • The t ype of o perat ionO pe n w ire ro p e (st ra n d e d ro p e) Lo o se sh e a ve (e .g . sh ea ve o n a ca b le w a y )Clo sed w ire ro pe Fixed shea ve (e .g . d ef lect io n shea ves)

These criteria lead t o d ifferent calculat ion procedures and fo rce considera tions for t he individua lloa d cases, rope types and types of operat ion.

3.1 Calculating the bearing compression

If t he rol ler bea ring is to be executed a s a f rict ion bea ring , the pv va lues in the be aring m ust becalcula te d a nd com pa red w ith th e permissible values fo r PA 6 G. The f rict ion be aring should beconsidered in the same w ay a s a press fit bea ring bush. In ot her w ords, the calculation is the sam eas for d ynamical ly loa ded frict ion b ea ring s. The expected b ea ring loa d is depen dent on t he t ypeof operat ion of the shea ve. For idler shea ves, the rope ten sion Fs can be used as the b ear ing loa dto calcula t e t he pv value of the rope tension.

Thus the a verag e surfa ce pressure for rad ial bea rings in idler shea ves is

FSp = ––––––– [MPa ]

d W. L

whe reFS = ro pe te nsio n in Nd W = sh a ft d ia m et e r in mmL = bea ring w id th in mm

and the average sliding speed is

d W. p .n

v = –––––––––– [m/s]60000

whe red W = sh a ft d ia m et e r in mmn = sp ee d in m in -1




Agg rega ted pvdurat ion for idler sheaves w ith dyna mic load ing become s

r FS i r d W

. p . n ipvdurat ion = u––––––––u . u––––––––––– u [MPa . m/s]

q d W. L t q 60000 t

In intermitten t opera tion it is possible t o correct pvdura t ion by t he pro cess de scribe d in th e section3.2 of th e cha pt er o n »Frict ion b ea ring s«.

For f ixed rol lers, the bea ring loa d is depen dent on t he an gle of cont act t ha t th e rope forms withth e shea ve. If t he shea ve is com plete ly encircled (180°), the ro pe t ension is do ub led in the calcu-la t ions. For a n a ng le o f conta ct a < 180° , a result ing force Fre s must be calcula t ed w ith the help ofthe a ngle and t he cable tension.

This is calculate d from the triang ular relationship and is

Fre s

= FS

2 - 2 . cos a [N]

whe reFS = cable ten sion in Na = ang le o f contact

For shea ves ma de from PA 6 G, the de te rmined p v va lues ma y not exceed 0.13 Mpa · m/s in d ryrunning a pplicat ions or 0 .5 Mpa · m/s with lubrica tion . If t he ca lcula t ed values exceed t hesema ximum values, an ant ifriction bea ring w ould be a dvisab le.

3.2 Calculating the compression between the rope and the sheave groove

The ma in criterion fo r the load bea ring capacity of shea ves is the compression bet w een t he ropea nd t he sheave. To calcula te t he compression, the Hertz ’ equa tions tha t ha ve been mo dif ied forth is case are used. The results of the calcula t ion s must b e compa red w ith th e permissible valuesfo r PA 6 G show n in Dia gra ms 3 an d 4. They must be considered in comb inat ion w ith th e speed o fthe rope and may no t exceed t hese values.

3.2.1 Point contact of closed wire ropes

If closed w ire ropes w ith a sma ll f leet an gle a re used (a < 10°), such as is th e case w ith cab lew a ys,th is causes con cent rat ed loa ding . The a rea o f pressure is elliptical.

Unde r these conditions the com pression pa rame ter p’ fo r shea ves ma de f rom PA 6 G is calculat ed

f rom the equa t ion

a

FS

Fres

FS

a

Fre s

FSFS

FS FS

2FS

180°




63,5 r 1 ip’ = –––––– . 3 eS ––e

2

. F [MPa ]y . h q R t

whe rey = correct ion va lue

h = Hcorrect ion va lueS 1

R = tot a l of t he principle curvatures in mm -1

F = shea ve lo ad in N

The sum of t he pr inciple curva t ures o f the bo dies tha t a re in conta ct w i th one a not her i scalculated f rom

1 2 1 1 2S ––– = ––– - ––– - ––– + ––– [mm –1]

R d r r D

From t he sum of t he principle curvat ures, th e correction a ng le c ca n be use d to d e te rmine the

correction values y a nd h according to t he fol low ing f ormula :

2 1 1 2–– + –– - –– - ––d r r D

cos c = –––––––––––––––1

S ––R

whe red = ro pe d ia me te r in mm r = rope curvat ure rad ius (ge nerally neg lig ible a s it is very large comp ared to ot her rad ii)r = g ro o ve ra d ius in mmD = g ro o ve ba se d ia me te r

The correct ion va lues y a n d h can be fo und in Ta ble 1. If c lies be t w een the t ab le va lues, thecorrection values must be inte rpolate d.

3.2.2 Point contact of open wire ropes

It can b e a ssumed f or sheaves ma de f rom PA 6 G tha t b ecause o f th e e las t ic ity o f the shea ve inco mbina t io n w ith a n o pe n st r a nde d ro pe , tha t no t o ne s ing le w ire f ro m the st r a nd lie s in thegroo ve but ra ther severa l w ires and tha t t hese par t icipa t e in the t ran smission o f pow er. There-fore, the e ntire stran d is rega rded a s a sing le w ire and i t is assumed t ha t a l l loa ded stran ds trans-mit the same pow er. In th e calcula t ion, a correcting f actor is introduced tha t t akes account of thepo w er tra nsmission of severa l stra nd s (ma ximum 40%).With this considerat ion the compression pa rame ter p‘ becom es

Xp’ = p ’e

. 3––– [MPa ]Z

and the compression pa rameter p‘e e fo r one sing le wirein comb ination w ith a PA 6 G shea ve is

r d 1 d 1 i2 F

p’e = 42 . 3 e1 - ––––+ ––––e. ––– [MPa ]q 2r D t d 2

1

whe re

Table 1: Correction values y and h for different values of c

c 90° 80° 70° 60° 50° 40° 30° 20° 10° 0°

y 1,0 1,128 1,284 1,486 1,754 2,136 2,731 3,778 6,612 ∞

h 1,0 0,893 0,802 0,717 0,641 0,567 0,493 0,408 0,319 0

Sheave loa d F

Shea ve loa d F




X = co rre ct io n f a ct o r in re la t io n t o p’e,fro m Ta ble 2

Z = numb er o f o ut er st ra nd sd 1 = st ra n d d ia m e t er in m mr = g ro ove ra dius in mm

D = g ro o ve ba se dia me te r in mmF = shea ve lo ad in N

3.2.3 Peripheral load with open wire ropes

In re g a rd to the po w e r t r a nsmissio n b e tw e e n the ro pe a nd the she a v e , the sa me a pp lie s a s toconcentra te d loa ding as described in i tem 3 .2.2. The o nly d if ference i s tha t the load on a com-pletely encircled pulley is not a point loa d b ut a uniform loa d.

Hence, the compression para met er p’ becomes

Xp’ = p ’e

. ––– [MPa ]

Zand the compression pa rameter p’e fo r a sing le w ire incombina tion w ith a PA 6 G shea ve is

(2r - d 1) . FSp’ = 55 . ––––––––––––– [MPa ]

2r . d 1. D

X = co rre ct io n f a c to r in rela t i o n to p ’efro m Ta ble 2

Z = n um b er o f o ut e r st ra n d sd 1 = st r a nd d ia me te r in mmr = g ro o ve ra d iu s in mm

D = g r oo ve b a se d ia m e t er in m mFS = ca b le t e nsio n in N

When d ete rmining t he correction f acto r, it should be con sidered t ha t w hen X > Z, Z = X must beinser ted in the ra dican d o f th e correct ion f ac to r so th a t the ra dican d i s 1 . If th e va lue o f p ’e isbet w een t he values given in the t ab le, the value fo r X must be interpolat ed a ccording ly.

Strand

d d1

Idler

FS FS

FS FS

Fixed sheave

Surface pressure p’e Correction factorin MPa X

≤ 50 Z

150 6

300 4

≥ 450 2,5

Table 2: Correction factor X




3.3 Maximum permissible surface pressures

The results f rom the ca lcula t ions must be compared w i th th e ma ximum permissible loa d para -met ers from Diag rams 3 and 4. It is not permissible to exceed the se values.

20°C

50°C

75°C

100°C

0

80

40

120

140

160

200

240

280

0 1 2 3 4 5 6m/s

Diagram 3: Loa d limit in relat ion to t he rope speed a nd a mbient t emperat ure for sheaves mad e from PA 6 G und erperipheral loa ding

M a x . p ’ i n M

P a

Diagram 4:Load l imit paramet er p‘max in rela t ion to the rope speed a nd a mbient tempera t ure for sheaves made f rom PA 6 G underconcentra ted loading.

20°C

50°C

0 0,5 1 2 3m/s2,51,5

40

80

20

100

60

120

0



Plastic gear wheels



P l a s t i c g e a r w h e

e l s

Plastic gear wheels

1. Use of plastics as a gear material

Althoug h thermo plastic g ears are unsuitab le for applicat ions in high performa nce gea rs an d fo rtran smitt ing high pow er, they ha ve opened up a broa d f ield o f a pplicat ion. The specif ic mate ria l

propert ies a l low use under condi t ions where even high qua l i ty meta l l ic mater ia ls f a i l . Forinsta nce, plastic ge ars must b e used if th e fo llow ing a re the key req uirement s:

• Maintenance-free• High w ea r resista nce w hen used in a d ry-running a pplication• Low no ise• Vibration d a mping• Corrosion resista nce• Low mass moment of inert ia throug h low w eight• Cost-effe ctive m an ufa cture

For a pla stic to be a ble to sat isfy the se req uiremen ts, it is a bsolutely vital tha t t he right m a terial is

chosen and t ha t th e design is carried o ut in a ma terial-relat ed ma nner.

1.1 Materials

Only a f ew th ermopla stics a re significan t fo r the ma nufa cture of g ea rs. The plastics a re describedin deta il in the previous cha pters, so here w e w ill only describe t hem in rega rd to to ot h fo rming .

• PA 6Universal g ear mat eria l fo r machine eng ineering ; i t is w ear resista nt and impact ab sorbing e venwhen used in rough condi t ions , less sui table for smal l gear wheels wi th h igh dimensiona lrequirements.

• PA 66Is more w ea r res ista nt t ha n PA 6 apa r t f rom w hen i t i s used w i th very smoo th ma t ing com-pon ent s, mo re dimension ally sta ble th a n PA 6 as it a bsorbs less mo isture, a lso less suita ble fo rsmall ge ar w heels w ith high dimensiona l requirement s.

• PA 6 GEssent ially like PA 6 and PA 66, ho w ever, it is especia lly w ea r resistan t due to its hig h d eg ree o fcrystallinity.

• Calaumid® 612 / 612 – Fe (PA 6/12 G )Toug h mo dified po lyam ide, suitab le for use in area s with impact-like loa d pe aks, we ar resista nce

compa rab le to PA 6 G.

• Calaumid® 1200 / 1200 – Fe (PA 12 G )Toug h-ha rd polyamide w ith rela t ively low tend ency to a bsorb w at er, hence, bett er dimensiona lstab ility tha n ot her polyam ides, especially suita ble fo r use in area s w ith impact-like loa d pe aks,excellent w ea r resistance.

• Oilamid®

Self-lubricating properties due to oil in t he p lastic, hence, excellent fo r dry running a pplication san d especia lly w ea r resista nt.

• POM – CBecause of its low moisture ab sorbing te nde ncy it is especially suitab le for small ge ars w ith high

dimensiona l sta bi li ty dema nds, not so loa da ble in dry running a pplicat ions due t o i ts hardness,how ever, if perma nent ly lubricate d, POM–C ge ars are more loa da ble tha n polyamide on es.

87




e l s

• PE – UHMWBecause of i ts low sta bi lity, it can only be used f or g ears that are no t subjected to high loa ds, goodda mping pro perties and chem ical resista nce, hence ma inly suitab le for use in a pplicat ion s w ithmechan ical vibra tion an d in chemically a g gressive e nvironmen ts.

1.2 Counterparts

Hardened s tee l i s the most sui table counterpar t regarding wear and ut i l i sa t ion o f the loadcarrying capa city , a s it ensures very go od dissipa t ion o f f r ic t ion hea t . In rega rd t o surface pro-perties, the same applies as w ith frict ion be arings: the harder t he steel the less wea r on t he w heela nd pinions. As a g uiding va lue, w e recomm end a ma ximum roug hness dept h of Rt = 8 to 10 µmbo th in lubricat ed op erat ion and in dry running ap plications.For g ea rs th a t a re no t subject t o h ea vy loa ds, it is possible to ma te plast ic/plastic. The surfa ceroug hnesses are insignifica nt f or w ea r.When choo sing a m at eria l, it should b e rememb ered t ha t t he driving pinions are a lwa ys subjectedto a higher level of w ea r. Conseq uent ly, the more w ea r resistant ma terial should a lwa ys be chosen

fo r the pinions (r pinion: steel, w hee l: plastic or pinion : PA, w hee l: POM).

1.3 Lubrication

The sta te ment s ma de in th e chapt er on »Friction be aring s«reg ard ing d ry running an d t he use oflubricant s a lso a pply here. Basical ly i t shou ld be n ot ed tha t insta l la t ion lubricat ion considera blyimproves the serv ice l i fe and the running- in behav iour . Mater ia ls tha t a re modi f ied wi th alubrica nt , such as Oilamid, ha ve much lon g er service lives tha n a l l ot her plast ics, even w itho utlubrication. Continuous lubricat ion w ith oil leads to b ett er heat dissipation a nd conseq uent ly to along er life and h igher levels of t ransmitted po w er.When t he compo nent i s lubr ica ted w i th g rease , the c ircumferent ia l speed should no t e xceed 5m/sec, as otherw ise the re is a d an ge r tha t t he g rease w ill be cast of f . Due to po lyam ide’s ten den cyto ab sorb mo isture , w a t er lubr ica-t ion i s no t recommended for po-lyamide components.

1.4 Noise development

Plastics in general have goodda mping prop ert ies. This con si-derably reduces noise on plast icg ea rs compa red to met al ones. Thediag ram opposite show s the soundintensi ty curves o f gear matesste el/ste el (a) a nd ste el/pla stic (b). Itshows maximum dif ferences of 9dB. Hen ce, steel/stee l is up to th reetime s as loud a s ste el/plast ic.

1.5 Manufacture

Plastic ge ars are ma nufa ctured w ith the sam e ma chining process as meta l gea rs (usually shaping

by the g enera t ing method and automa t ic hobbing).As the cutt ing fo rces a re very low, the pro file can be ma nufa ctured in one cycle w ith high fo rw ardfeed rat es, w hich in turn reduces ma nufa cturing costs.When ma nufa cturing w ith high forw ard f eed ra t es, corrugat ed surfa ces can be prod uced. At f irstthe se g ive an unfa vourable impression . How ever, in dry running appl ica t ions the f a ces o f the

dB

80

70

60

500 1000 2000 2900U/min

a

b

Stee l CK 45

Polyamide 6 G




e l s

tee th a re quickly smoothed a f ter a short running- in per iod . In lubr ica ted appl ica t ions , thecorrugat ed f orm acts as a lubricat ion po cket w here the lubricant can collect – to the a dvanta ge ofthe g ea r. In ot her w ords, this corrug at ion is no red uction in qua lity.Basica l ly w hen m achining plast ic ge ars , depending on t he mo dule , qua l it ies o f 9 to 10 can beachieved. Rega rding t he to o t h qua li ty tha t can be a chieved, it should be no ted t ha t the ro l ling

to ot h flanks of plastic g ea rs ea sily fit one a not her. Therefo re, great er tolerances are a llow ed t ha nw ould b e th e case w ith met a l gea rs. This especially applies to pow er tra nsmitt ing pinions. For th egra de t ha t is exclusively rela t ed t o t a ng ent ia l compo site error Fi" a nd t a ng e n t i a l t o o th-to -to o therror f i" th is means tha t up to tw o g rades more a re permit t ed tha n for simi la r gea rs mad e f rommeta l . The to o t h play is increa sed b y one to t w o g rade s compared t o s tee l to compensa te f ortemperat ure and moisture ef fects.

2. Design information

The fo llow ing desig n info rmat ion is intend ed t o a ssist wh en dimensioning n ew ge a r compo nent s.Exist ing da ta should be used for ge ar design s tha t a re in use and w hich have been t r ied a ndtested.

2.1 Width of the tooth face

For plast ic ge ars there is ba sical ly no prob lem in extend ing t heir widt h to th e same size a s thediamet er. Determining the sma llest w idth is depen den t upo n th e a xial stab ility of th e g ea r. No t estresults are avai lab le in rega rd to the connection b etw een the life of the component and the w idthof the to oth fa ce or rega rding a d eterminat ion of the optimum width of to oth fa ce.Practica l experience has, how ever, show n tha t t he w idt h of the t oot h fa ce should b e a t least six to

eight t imes the mo dule.For t he ma ting compo nent s ste el/plastic it is bet ter t o d esign the plastic g ea r slig ht ly sma ller th anthe s tee l p in ion to make sure tha t t he plast ic gea r is loa ded across the ent i re w idth o f the t oo t hfa ce. A similar situa tion a rises w ith th e ma ting compo nen ts plastic/plastic, w here t he d imension s ofth e ge ar on w hich the h igher w ea r is expected should be slight ly na rrow er. This prevents w ea r onthe ed ge s of t he teet h, wh ich could af fect the running beha viour.

2.2 Module, angle of pressure and number of teeth

The load bea r ing capaci ty o f p las t ic gea rs can be d i rect ly a f fected by the choice o f mo dule andan gle o f pressure. If , w hile ma intaining t he sam e peripheral force, the mod ule/an gle o f pressure isincreased, the roo t-streng th o f t he te eth increases. How ever, compa red to steel ge ars, the actua lincrease is less, as the ef fective contact ra t io factor decreases and i t is no longer possible forseveral teet h to eng ag e simulta neously. A higher conta ct ra t io fa ctor, how ever, can b e bet ter fo rthe loa d b earing capa city tha n increasing the root-streng th o f a n individua l toot h. We can d erivethe f ollow ing connection fro m this (ap plies mainly to slow running or impact load ed g ea rs):

• Preferab ly a sma ll mod ule for to ugh elastic the rmoplastics (increase in the cont a ct ratio f a ctor, rseveral teeth engaged simultaneously)

• Preferab ly a larg e mod ule fo r hard t hermoplastics (increase in the root -strengt h of the t eeth, a sa higher cont act ra t io f actor is not possible due to the inferior defo rmation beha viour)

In the case o f gea rs w i th a h igh per iphera l speed, a t tent ion must be pa id tha t the mo vement i snot a f f ected by the ef fective cont act ra t io fa ctor.

The a ng le of pressure fo r involute t eet h is de f ined a t 20° . Neverthe less, i t can o cca sion a llybe necessary to chan ge t he an gle o f pressure (e .g . to d ecrease the numb er o f tee t h or reduce




e l s

running noise). Ang les of pressure < 20° lead t o t hinner and hence less loa da ble teet h w ith steeptoo th prof iles but low running noise.Angles o f pressure > 20° produce sharper, th icker tee th w ith a grea ter root -st rengt h a nd f la t terprofiles.In rega rd to t he number o f tee t h , it should be noted for h igher per iphera l speeds tha t the ra t io

bet w een the numb er o f tee t h ma y not be an in teg er mult ip le . If th is i s the case , the same t ee thalw ays enga ge, w hich encourag es w ear.

2.3 Helical gearing

Experience ha s show n t ha t h e l ica l p las t ic gea rs run q uie ter w i th a sma l l he l ix ang le tha n spurto ot hed types . How ever, the expected increase in the load bea r ing ab i lity i s sma l ler tha n i s thecase wi th s tee l gea rs. Altho ugh t he lengt h o f t he f a ce cont act l ine increases an d t he load i sdistributed amo ng several teet h, the load is uneven a nd t he tee th a re deformed. This nega tes thead vanta ge of he lica l gea ring t o a certa in deg ree.As w ith meta l ge ars, hel ica l to ot hed plast ic g ea rs are calcula ted via a spur to ot hed spare w heel .b ≈ 10° – 20° is regarded as being a fa vourab le helix ang le.

2.4 Profile correction

Profile corrections a re g enera lly necessa ry w hen

• a gea r pair has to b e ad apt ed t o suit a specif ied axle ba se(positive or negative profile correction)

• the number of teeth is not reached a nd t his causes undercut(po sitive pro file correction)

In the a ppl ica t ion , a t ten t ion should be pa id tha t in the case o f neg a t ive pro f i le correct ion t heunde rcut i s no t to o g rea t . This w ould resul t in a grea t ly minimised roo t-s t rength o f the t ee th ,w hich could reduce the life a nd loa d b earing capacity of the g ear.Vice versa, in the case of positive prof ile correction, t he t hicker too th root could cause a loss in t hedefo rmation capab ility a nd a subsequent reduction in the conta ct ra t io fa ctor.

2.5 Flank clearance and crest clearance

Because o f t he h igh th ermal expan sion f ac to rs o f p las t ics w hen dimensioning g ea rs, a t t ent ionmust b e pa id t o t he ma ter ia l-re la t ed f i t t ing o f the f l ank and crest c learan ces so t ha t a minimumflank clea rance is g uara ntee d. When plast ic ge ars are used, i t ha s proven practica l to ma inta in aminimum fla nk clearan ce of ≈ 0.04 · mo du lus.The bu ilt-in flan k clea ran ce is thus

Se = Seo + 2l . sin a (ka. kF) [mm]

whe reSeo = minimum f lank clearan ce in mml = to t a l d ist a nce co nsist ing o f p la st ic be twe e n the two ro t a t i o na l a xe s in mma = ang le of pressureka = coef f icient o f elonga tionkF = correction fa ctor for moisture a bsorption (to b e used fo r polyamides, can b e foun d in the

cha pt er o n »Frict ion be a ring s«)

For t he inb uilt crest clea ran ce, a me a sure of 0 .3 · mod ule ha s proven to be practica l . This ta kes

account o f t empera ture f luctua t ions o f up to ± 20° C and a lso ma kes ad equa te considera t ion fora ny ina ccuracies in the t oo the d g ea rs.




e l s

2.6 Power transmission

The fea the r key and g roove type o f conne ct ion t ha t i sge nera l ly used in machine eng ineer ing i s a l so used forplast ic g ea rs. For a conne ction such a s this, the f lank of

the key groove must be e xamined t o ensure tha t i t doesno t e xceed th e pe rmissible surfa ce pressure. The surfacepressure is

Md. 103

pF =i . rm

. h . b [MPa]

whe reMd = transmitt ed to rque in Nmi = n um be r o f g ro ove f la nksrm = r a d ius f ro m the ce n t re o f the sha f t t o t he

centre of the b earing f lank in mmh = h e ig h t of t he b ea rin g fla n k in mmb = w id t h o f th e b e a rin g fla n k in mm

The va lue produ ced fro m t he calcula t ion isco mpa re d w ith D i a g ra m 1 a nd ma y no t e xce e dth e ma ximum p ermissible va lues.

However , i t should be noted tha t th is va lueconta ins no saf ety f actor f or shock-type load s orsa fe ty reserves . Depending on the load , werecommend a sa f ety fa ctor of 1 .5 to 4 .

Because of t he no tch sensitivity of plastics w hen

key groo ves are being ma nufa ctured, a t t ention should be paid tha t the ed ges are designed w ith arad ius. How ever, this is ge nerally not possible be cause the usual cutting to ols an d f ea the r keys aresharp ed ged . When la rger to rques a re be ing t ransmit t ed t h is can a lso cause defo rmat ion in thehub.

I f the ca lcula t ion o f the f l ank pressureshould produce h igh pressure va lues tha ta re no t permissible , or if hub def ormat ionis fea red, t here a re several possibi li t ies ofpow er tran smission a vaila ble.

One p ossibility is th e no n-po sitive conn ec-

t io n o f t he w he e l bo dy w ith a st e e l in se r t .This is screw ed to th e w hee l bo dy. Thediagram opposi te shows one possibledesig n solution.

For f ixing the steel insert we recommendhexagon socket screws according to DIN912, property class 8 .8 or better in thefo llow ing dimensions.

rm

b

h

PA 6 G /POM30

20

10

00 20 40 60 80 100

MP a

Ambient temperature

Diag ram 1: Guiding value for permissible

surface pressure

Tip Number Screwdiameter of screws size

up t o 100 mm 3 M 6

up t o 200 mm 4 M 8

a bo ve 200 mm 6 M 8 /M 10




e l s

For g ea rs w ith relat ively thin w a lls, it is a dvis-ab le to u se hexag on socket screw s w ith a low hea d a ccord ing t o DIN 6912, prope rty class 8.8or bet ter.

One a l terna t ive to t he use o f a screw ed s tee lf i t t ing is to design th e g ea rs in Cala umid 612Fe o r Cala um id 1200 Fe. The me ta llic corewhich i s connected to the plas t ic bo th in afo rm-fit an d no n-positive ma nner ena bles th esha f t-hub connection to be calcula t ed a nd d i-mensioned l ike a meta l l ic component asusual . The fo rm-fi t an d no n-posit ive connec-tion be tw een t he plastic casing a nd t he met allic core is crea ted w ith a knurl.

3. Calculating thermoplastic gears wheels

The reasons for the premat ure breakdow n of thermoplastic gea rs are g eneral ly the same d ama gea spects an d p rinciples tha t o ccur in meta llic g ea rs. This is w hy th e calcula tion of plastic ge ars do esnot di f fer in principle from the know n m etho ds. The o nly di f ference is tha t the ma teria l-specif icproperties of plastics are included in th e calculations in the f orm o f correction fa ctors.

3.1 Torque Md, peripheral force FU and peripheral speed v

The t o rq ue is The periphera l fo rce is The periphera l speedis calculated a s

P Md d 0 . p . nMd = 9550 . –– [Nm] FU = 2 . 103 . ––– [N] v = –––––––––– [m /s]n d

060 . 103

w here w here w hereP = pow er in kW Md = t o rq ue in Nm d 0 = reference diamet er in mmn = speed in min -1 d 0 = re ference diameter n = speed in min -1

in mm

3.2 Tooth body temperature cZ and tooth flank temperature cFin continuous operation

As wi th a l l design s made f rom thermoplas t ic mat er ia ls, tempe ra ture a lso plays a ma jor ro le for

gea rs in rega rd to t he load bea ring capa city of t he component. A dist inction is made bet w een thetoot h bod y tempera ture cZ and the to o th f lank tempera ture cF.

The to o t h bo dy tempe ra ture i s responsible for the permissible to o t h root loa ding a nd t oo thdefo rmation, w hereas the too th f lank temperat ure is used t o roug hly estimate the level of w ear.

How ever, it is very dif f icult t o d etermine these tw o temperat ures accurately, as on a rota t ing g earw heel the hea t tra nsmission coeff icient can on ly be estimat ed roug hly. Conseq uent ly, any a rith-met ica l de termina t ion o f the t empera t ures i s l iab le to ha ve a certa in amount o f e rror. In pa r t i -cular, w hen t he t oot h f lank tempera ture is being calcula t ed, q uite of t en high values are producedw hich, in some cases, are even a bo ve the melt ing t emperat ures of the plast ics. How ever, in prac-tice no melting of the to ot h prof i le ha s been ob served. Nevertheless, the values can be reg arde da s characte ristic and com pa rison tem perat ure values.

It can b e assumed t ha t th e excessive calcula ted values w ould gu ara nte e a d esign w hich is on t hesafe side in any case.

Calaumid

Steel

Knur DIN 82 – RKE 2,0




e l s

For the the rmal ca lcula t ion o f the g ea rs, the f r ic t ion hea t , the hea t d issipa ted f rom the g ea rw heel in the g ear room a nd the he at tha t is dissipat ed from t he gea r room t o the o utside must beconsidered.

Under these condit ions, w e ge t t he fol low ing:

i + 1 r k2. 17100 k3

ic1,2 = cU + P . m. 136 . –––––––––––– . e ––––––––––––––––– + 7,33 . ––– e [°C]

z1,2

+ 5i q b . z1,2

. (v . m) 34 A t

whe re

Inde x 1 fo r the pinionIndex 2 for the w heelcU= a mbie n t t e mpera ture in °C b = w id th o f the to o th f a ce in mmP = pow er in kW v = periphera l speed in m/secµ = coef f icient o f f r ict ion m = module in mmz = teeth A = surf a ce o f the g ea r ca sing in m 2

i = t r a nsmissio n ra t i o z1/z2 w ith k2 = mat eria l-rela t ed fa ctorz1 = number of teeth in pinion k3 = gea r-rela t ed fa ctor in m 2 K/W

For fa ctor k2 the fo llow ing must be included d epending on t he temperat ure to be calcula t ed:

Calcula t ion of f lank temperat ure: Calcula t ion of root temperat ure:

k2 = 7 fo r ma ting compon ent s stee l/plastic k2 = 1.0 for ma ting compon ent s stee l/plastick2 = 10 fo r ma ting compo nen ts plastic/plastic k2 = 2.4 fo r mat ing comp on ent s plastic/plastick2 = 0 in the case of oil lubrication k2 = 0 in t he case of oil lubricationk2 = 0 a t v ^ 1 m/sec k2 = 0 a t v ≤ 1 m/se c

For fa ctor k3 and the coeff icient o f f rict ion µ, the f ol low ing must b e included independen t o f t hetemperat ure to be calcula t ed:

k3 = 0 for completely open g ear m 2 K/Wk3 = 0.043 to 0.129 for pa rtially open g ea r in m2 K/Wk3 = 0.172 for closed g ea r in m2 K/W

µ = 0.04 fo r g ea rs w ith perma nent lubricat ion µ = 0.4 PA/PAµ = 0.07 fo r g ea rs w ith oil mist lubrica tion µ = 0.25 PA/POMµ = 0.09 fo r g ea rs w ith a ssembly lubrication µ = 0.18 POM/Sta hlµ = 0.2 PA/ste el µ = 0.2 POM/POM

3.2.1 Tooth body temperaturecZ and tooth flank temperaturecF

in intermittent operation

Ana log ous to frict ion bea ring s, because of the low er amo unt o f hea t caused by frict ion, g ea rs inintermitt ent opera tion a re increasing ly load ab le the low er th e d uty cycle. The rela t ive d uty cycleED is considered in the e q ua tion in section 3.2 by introd ucing a correction fa ctor f .

The re la t ive dut y cycle is de f ined a s the ra t io be t w een t he loa d d ura t ion t and the overa l l cycletimeTas a percentag e.

tED = –– . 100 [%]T

whe ret = to ta l o f a l l load t imes w ith in the cycle t ime Tin minT = cycle t ime in min




e l s

For t hermo plastic gea rs, th e o verall cycle time isdef ined a s T= 75 min. The t ot a l of a l l individua lload t imes occurring within this 75 min formsthe load dura t ion t .

With the va lue tha t ha s been ca lcula ted in th ismanner i t i s now possible to de termine thecorrect ion f ac to r f f rom Diag ram 2 . At t ent ionsho u ld be pa id tha t e a ch lo a d d ura t i o n w h ichexceed s 75 min (reg a rdless of w het her t his isonly once) is evaluat ed a s a continuous loa d.

Taking a ccount of the correction fa ctor, the to oth f lank temperature and too th b ody t emperatureis

i + 1 r k2. 17100 k3

ic1,2 = cU + P . f . m . 136 . –––––––––––– . e ––––––––––––––––– + 7,33 . ––– e [°C]

z1,2 + 5i q b . z1,2. (v . m) 3

4 A t

The va lues given in section 3.2 can b e used f or t he f a cto rs k2, k3 an d t he coeff icient of friction µ.

3.3 Calculating the root strength of teeth

If t he t oo t h root st ress j F exceed s the permissible stress j Fper under load ing , i t m ust be assumedtha t t he te e th w ill break. For th is reason the t oo t h root st ress must b e ca lcula t ed a nd compa redw ith the permissible values. If t he pinion a nd ge a r are constructed f rom plast ic, the calcula t ionsmust b e carried o ut separately for each of th em.

The t oo th ro ot stress is

FUj F = –––––– . KB. YF

. Yb. Ye [MPa]

b . m

whe reF

U= peripheral force in N

b = g e a r w id th in mm (w he re the w id th o f the pin io n a nd g e a r d if f e r: use the sma lle r w id th + mas a ca lcula t ion value for the w ider gear)

m = mo d ule in mmKB = operat ing factor f or di f ferent t ypes of drive operation, f rom Tab le 2YF = too t h shape f a ctor f rom Diag ram 3Yb = he l ix f ac tor to ta ke account o f the increase in loa d b ear ing capa city in he l ica l gea r ing , a s

this is the case w ith plastic ge ars, this value is to be set as 1.0Ye = contact ra t io fa ctor from Tab le 1, w here Ye = 1/ea und ea = ea z1 + ea z2

1,0

20 40 60 80 100

0,8

0,6

0,4

0,2

Diagram 2: Correction factor for ED

C o r r e c t i o n f a c t o r f

Relative duty cycle (%)




e l s

z 14 15 16 17 18 19 20 21 22 23 24

eaz 0,731 0,740 0,749 0,757 0,765 0,771 0,778 0,784 0,790 0,796 0,801

z 25 26 27 28 29 30 31 32 33 34 35

eaz 0,805 0,810 0,815 0,819 0,822 0,827 0,830 0,833 0,837 0,840 0,843z 36 37 38 39 40 41 42 43 44 45 46

eaz 0,846 0,849 0,851 0,854 0,857 0,859 0,861 0,863 0,866 0,868 0,870

z 47 48 49 50 51 52 53 54 55 56 57

eaz 0,872 0,873 0,875 0,877 0,879 0,880 0,882 0,883 0,885 0,887 0,888

z 58 59 60 61 62 63 64 65 66 67 68

eaz 0,889 0,891 0,892 0,893 0,895 0,896 0,897 0,898 0,899 0,900 0,901

z 69 70 71 72 73 74 75 76 77 78 79

eaz 0,903 0,903 0,904 0,906 0,906 0,907 0,909 0,909 0,910 0,911 0,912

z 80 81 82 83 84 85 86 87 88 89 90

eaz 0,913 0,913 0,914 0,915 0,916 0,917 0,917 0,918 0,919 0,919 0,920

z 91 92 93 94 95 96 97 98 99 100 101

eaz 0,920 0,921 0,922 0,922 0,923 0,924 0,924 0,925 0,925 0,926 0,927

2,0

2,2

2,4

2,6

2,8

YF

3,0

3,2

3,4

3,6

x = 0 , 0

- 0 , 0

5 - 0 , 1

- 0 , 2

- 0 , 3

- 0 , 4

- 0 , 5

- 0 , 6

0 ,0

5

0 ,1

0 , 2

0 ,3

0 ,4

0 ,5

0 ,6

0 ,7

0 ,8

15 16 18 19 20 25 30 40 50 60 80 100 200 40017

35 45 70 90 150 300Z

x = Prof ile correction

Mode of operation Mode of operation of the driven machineof the driving machine Even Moderate Average Strong

impact impact impact

Even 1,0 1,25 1,5 1,75

Mo dera t e impa ct 1,1 1,35 1,6 1,85

Avera g e impa ct 1,25 1,5 1,75 2,0

St ro ng impa ct 1,5 1,75 2,0 2,25

Tab le 1: Partial tra nsverse cont act ra tio fo r gea rs w ithout profile correction

Tab le 2: Operat ing f acto r KB

Diag ram 3: Toot h fo rmation f actor YF as a function of t he number of teeth




e l s

In the case of prof ile corrected to oth ed g ears the fa ctor Ye must be a djusted accordingly.The f ollow ing a pplies:

z1r z2

i z2ea = ––––––. (tanaE1 - ta naA1) and tanaA1 = t a natw . e1 + ––– e- ––– ta naA2

2 . p q z1 t z1

The va lue ta naE1 is depe nde nt on the The value ta naA2 is dependent on theco rrect io n va lue co rrect io n va lue

d K1 d K1D1 = –––– D2 = –––d G2 d G 2

w here w hered K1 = outside diameter of pinion d K2 = outside d iameter o f l a rge w heeld G2 = b a se d ia met er o f la rg e w heel d G1 = ba se diameter of pinion

The values for t a naE1 a n d t a naA2 can b e ta ken from Dia g ram 5. The ef fective pressure a ng les at w

a n d t a n at w are ca lcula t ed f rom t he pro f i le correct ion x1, 2 a n d t h e n u m b e r o f t e e t h z 1, 2 w h e r eInde x 1 stan ds for t he pinion a nd Inde x 2 fo r the large g ea r. The ef fective pressure a ng les fo r spur

gea rs are show n in Diag ram 4.

3.4 Calculating tooth profile strength

Excessive pressure o n t he t oo th prof ile can ca use pitting or excessive w ea r. The w ea r is part icularlyobv ious in the root a nd crest o f the too th , w hich chang es the t oo t h format ion a nd consequent lyleads to une ven transmission of mo tion.

In orde r to prevent prema ture fa ilure due t o excessive w ea r or pitt ing, the t oo th f lank pressure j Hmust be det ermined. The pressure occurring on the to ot h flan k is

FU. (z1 + z2)

j H = –––––––––––––– . KB. Ze

. ZH. ZM [MPa]

b . d 0. z2

whe reFU = peripheral fo rce in N d 0 = ref e re nce d ia me te r in mmz1 = number of teeth in pinion KB = o pe ra t ing f a c to r f o r d if f e re n t

z2 = number of teeth in large gea r types of drive operation, f romb = g e a r w id th in mm (w he re the w id th o f Ta b le 2

the pinion and gea r di f fer: use the Ze = co n t a ct ra t io f a ct o rthe smaller w idth + m as a ca lcula t ion ZH = zo ne f act orvalue for the w ider gea r) ZM = m a t eria l f a ct o r

35

0 0,02 0,04 0,06 0,08

30

25

20

15

Diagra m 4: Effective pressure ang le atw , t a natw

atw

(x1 + x2 )/(z1 + z2 )

t a nat w

10

0,10

0,7

0,6

0,5

0,4

0,3

0,2

t a natw atw ,

1,0 1,1 1,2 1,3 1,4

Diagram 5: Correction diag ram fo r transverse contact ra tio

D1, D 2

t a n a A 2 , t a n a E 1

1,0

0,8

0,6

0,4

0,2

0




e l s

The conta ct ra t io o f severa l tee t h a c ts l ike a w idening o f the to o t h . This appa rent w idening i sta ken account of w ith the conta ct ra t io fa ctor Ze and eq uat ed fo r spur and helica l gea rs.

The conta ct ratio fa ctor becomes

4 - (eaz1 + eaz2)Ze = ––––––––––––––––

3

whereeaz1 = par t ia l t ransverse contact ra t io o f p in ion

fro m Ta b le 1eaz2 = p a r t ia l t r a n sve r se c o n t a ct r a t i o o f l a r g e w h e e l

fro m Ta b le 1

The t o o t h f o rma t io n f a c to r ZH t a ke s a cco un t o f theto ot h f lan k disto rt ion. In t he case o f n on-prof i le correc-te d spur t e e th w ith a n a ng le o f p re ssure o f a = 2 0° t he

z o ne f a cto r ca n be a ppro x ima t e d w ith ZH = 1.76. Fo rprof i le corrected spur tee th ZH ca n b e t a ke n f ro m thediagra m opposite .Fo r a ng le s o f p re ssure o the r tha n 20° the f o llo w ingapplies:

1 1ZH = ––––––– . –––––––

co sa t a nat w

wherea = normal ang le of pressuret a n at w = ef fective pressure ang le from Diag ram 4

The elasticity of the p lastic a nd conseq uent ly the e ffective cont act surface of t he t oo th prof ile areconsidered w ith t he ma teria l fa ctor ZM.

It can be said w ith sufficient accuracy tha t

E1. E2ZM = 0,38 . E’ a nd E’ = ––––––––

E1 + E

whereE1 = dyna mic mod ulus of e lasticity of t he pinionE2 = dynamic modulus of elast ici ty of the gea r

The dif ferent mo duli of di f ferent mat eria ls for the pinion a nd g ear ha ve been ta ken into account.

For t he m at ing compo nent s p las t ic/stee l t he correspond ing f a c tor fo r ZM ca n be t a ke n f ro mDiag ram 8.

For the mat ing components of g ears made from th e same plast ic the f ol low ing applies:

1Z M(K/K) = ––––. ZM(K/St )M 2

If t he g ear a nd pin ion a re mad e f rom d if ferent p last ics, the f a c tor ZM (K/St) for t he sof te r pla sticshou ld be used.

The t oo th flank te mpera ture is det ermined w ith th e help of the fo rmula in sections 3.2 or 3.2.1.

Diagram 6: Zone factor ZH

with prof ile correction a nd a = 20°

Z H

(x1 + x2 )/(z1 + z2 )

2,0

1,9

1,8

1,7

1,6

1,5

1,4

1,3

1,2

1,10 0,02 0,04 0,06 0,08 0,1




e l s

105

106

107

108

70

60

50

40

30

20

10

0

20 °C

60 °C

80 °C

100 °C

Toot h tempe rature

Diagram 9: Root strength o f teeth j Fmax für POM

Load alternations

R o o t s t r e s s j F m a x

MP a

105

106

107

108

109

60

50

40

30

20

10

0

60 °C

120 °C

Toot h tempera ture

20 °C

40 °C

80 °C

100 °C

Diagram 10: Root strength of t eeth j Fmax fo r PA 6 G

Load alternations

R o o t s t r e s s j F m a x

MP a

Flank tempera ture (°C)

20

40

60

80

100

120

140

Diagram 11: Contact surface pressure j Hmax ,PA 6 G, dry running

C o n t a c t s u r f a c e p r e s s u r e j H m a x

105 106 107 108 109

70

60

50

40

30

20

10

0

MP a

Load alternations


40

80

100

120

Diagra m 14: Cont act surface pressure j Hmax ,POM, dry running


140

120

100

80

60

40

20

0105 106 107 108 109

20

Load alternations

MP a

Load alternations


MP a

105 106 107 108 109

140

120

100

80

60

40

20

0

Diagram 13: Contact surface pressure j Hmax

,PA 6 G, oil lubrication

20

40

60

80

120

140

100


Diagra m 12 : Cont act surface pressure j Hmax , PA 6 G, g rease lubrication



MP a

140

120

100

80

60

40

20

20

40

60

80

100

120

140

Load alternations

105 106 107 108 1090



Plastic spindle nuts



P l a s t i c s p i n d l e n u t s

102

1. Plastic as a material for spindle nuts

Spindle nuts , in combina t ion w i th a t hread ed spindle , t ransform a t urning mot ion in to a linearmot ion . Good sta bi lity o f th e nut ma ter ia l , a la rg e thread bea r ing a rea an d h igh surface qua lity

a re ad vant ag es for pow er tran smission. A tra pezo idal screw threa d d esign according t o DIN 103 isad vanta geo us and pra ctica l .Loa ding o f the t hread f l anks i s the same a s on a sl id ing e lement w hich mea ns tha t in reg ard t ochoosing a suita ble mat er ia l for t he spindle nut , th e ma in considera t ions a re slid ing an d w ea rproperties. The stab ility of the chosen ma terial is decisive f or saf e pow er t ransmission.It should be no ted tha t g lass fibre reinfo rced plastics are unsuitab le for the ma nufa cture of spindlenut s. Compared to ot her the rmoplastics, the y exhibit inferior sliding a nd w ea r values. In a dd ition,the glass fibres can cause increa sed w ea r in t he ma ting componen t. The relatively high mo dulus ofe las t ic i ty o f these mater ia ls a l so h inders de format ion o f the thread during s t resspea ks, so t ha t t he loa d can distribute evenly over all the t hrea ds. This results in te ars in t he t hreadan d a much shorter service life compa red to plastics that are n ot reinfo rced.

1.1 Materials

For the m a nufa cture of spindle nuts, ca st po lyam ides w ith an d w ithout sliding ad ditives, as w ell asPOM, PETand PETw ith sliding ad ditives have proven t heir wo rth.In regard to service l i fe , l ike a l l other sl iding applicat ions, the use of materia ls with buil t- inlubrica tion (such a s Oilamid a nd PET-GL) is a n a dva nt a g e. Compa red t o o th er plastics, the y exhibitless w ea r an d t hus achieve a longe r service life.

1.2 Lubrication

As with a ll ot her slide a pplications, lubricat ion is not a bsolutely necessa ry, but am ong ot her thing si t do es considera bly prolong the service l ife o f t he compo nent s. It a lso count eracts the d an ger o fstick-slip occurring.An init ia l insta l la t ion lubrication is pract ica l , as recommen de d f or frict ion b ea ring s an d slidingpa ds, w ith a subseque nt empirica l lubrica tion . This especia l ly a pplies to high ly stressed spind lenuts wh ere a t t ention ha s to be pa id that the frict ion heat is dissipat ed.How ever, gra phite should n ot be used as a lubricant in combinat ion w ith polyamide spindle nuts,a s wit h t his comb inat ion stick-slip becom es more likely.

2. Manufacture and designThe th read s of spindle nuts can be m achined o n suita ble machine to ols. We recom mend tha t t heybe prod uced on a l a t he w i th the use o f a l a th e threa d chise l . In th is w ay , it can be en sured tha tthere is enoug h play on t he f lanks of t he thread to b alance out the ef fects of hea t expansion a ndmoisture absorption.General ly the spindle nut an d h ousing are connected via a fea ther key. The load bea ring capacityof plastic nuts in t his case is orient ed to the ad missible compression in the f ea the r key g roove.To f ul ly uti lise th e load bea ring capacity o f t he plast ic threa d, a form-fi t connection bet w een t heout er stee l housing an d t he plastic nut is requ ired.

Plastic spindle nuts




3. Calculating the load bearing capacity

3.1 Surface pressure in the key groove

For a fea ther key connect ion , the s ide o f t he key groove must b e checked to ensure tha t i t do es

no t exceed t he pe rmissible surfa ce pressure.The surfa ce pre ssure is

Md. 103

PF = –––––––––––––– [MP a ]i . rm

. h . b

whe reMd = transmitted torq ue in Nmi = n um be r o f g ro o ve fla nksrm = radius from the middle of the shaf t to

the middle of t he bea ring f lank in mmh = h eig h t o f t he b ea r in g f la n k in mmb = w id t h of t he b ea rin g f la n k in m m

The va lue f rom t he ca lcula t ion is compa red w ith Diag ram 1 and ma y not exceed the m aximumvalue.

3.2 Surface pressure on the thread flank

If w e assume t ha t a ll threa d flan ks bea r the load eq ua lly, the surface pressure on t he flan ks is

Fp = –––––––––––––––––––––––– [MP a ]

r l i 2

z . H . ed 2. p . –– e + l2

q P t

whe reF = ax ia l load o f the spindle in NP = le ad in mmd 2 = f lank diamet er in mml = le ng t h o f nu t in mmH = depth f or ISO metric trapezo ida l screw

threa d in mm a ccording to Tab le 1z = numb er of screw f l ight s

(in case o f multiple-flight s)

In t he ca se of sta tic loa ding fo r spindle nut s mad e fro m PA, POM or PET, at 20° C appro x. 12 MPaan d a t 80° C ap prox. 8 MPa can b e permitted as the ma ximum compression.

103

PA 6 G /POM

30

20

10

0

MPa

0 20 40 60 80 100

Ambient temperature

Diagram 1: Guiding values for permissiblesurface pressure

S u r f a c e p r e s s u r e

P

30°

d d 2 = D 2

d 3

H




104

Tab le 1: ISO metric trapez oida l screw t hrea d a ccording to DIN 103

Threa d Threa d Threa ddiameter P H d2 diameter P H d2 diameter P H d2

d = 0,5 . P = d - H d = 0,5 . P = d - H = 0,5 . P = d - H

8 1,5 0,75 7,25 36 6 3 33 75 10 5 70

10 2 1 9 40 7 3,5 36,5 80 10 5 75

12 3 1,5 10,5 44 7 3,5 40,5 85 12 6 79

16 4 2 14 48 8 4 44 90 12 6 84

20 4 2 18 52 8 4 48 95 12 6 89

24 5 2,5 21,5 60 9 4,5 55,5 100 12 6 94

28 5 2,5 25,5 65 10 5 60 110 12 6 104

32 6 3 29 70 10 5 65 120 14 7 113

3.3 Sliding friction on the thread flank

As the t hread f l anks can be considered , a s a sl id ing e lement , th e pv va lue can a lso b e used a s ag uiding value for sliding friction loa ds fo r spindle nuts.For t he t hread flank th is is

n . (d2. p)2 + s2

pv = p . –––––––––––––––––– [MPa . m/s]60000

whe ren = numb er o f st ro ke s in 1/m in –1

d 2 = f la nk d ia meter in mm

s = st ro ke leng t h in mm

As with friction b ea ring s, the q uestion reg ard ing t he pe rmissible sliding friction loa d is a prob lemcaused by the hea t th a t occurs due t o f r ict ion . If i t can be ensured tha t t he plas t ic nuts ha vesuff icient t ime to cool do w n in intermittent o peration, higher values can be permitted tha n in thecase of cont inuous opera tion.

How ever, the det ermined values may n ot exceed the ma ximum va lues given in Tab le 2.

Tab le 2: pv – limiting values fo r spind le nut s

P A 6 G

O i l a m i d

P O M – C

P E T

P E T – G L

P A 6 G

O i l a m i d

P O M – C

P E T

P E T – G L

Continuous operat ion Intermitten t operat ion

Dry running 0,15 0,23 0,15 0,15 0,25 0,23 0,34 0,23 0,23 0,37

Continuous lubrica t ion 0,30 0,30 0,30 0,30 0,50 0,45 0,45 0,45 0,45 0,50



Tolerances



T o l e r

a n c e s

Tolerances

1. Material-related tolerances for machined plasticconstruction parts

Plastics are o ft en integ rat ed int o existing a ssemb lies to replace convent iona l mat erials. As a rule,however , the product ion drawing i s only a l tered in respect to the new mater ia l . Of ten theto le ra nce s tha t ha ve be e n spe cif i ed f o r the s te e l co mpo ne n t a re no t a da p te d t o su it t he ne wma terial. But even in the case of ne w designs w here plastic is planned as a ma terial, the t olerancefields tha t a re norma l for stee l are still used.How ever, the special fea tures of plastics exten sively preclude th e choice of the na rrow produ ctionto leran ces requ ired f or steel parts.

The d ecisive fa ctor is not th e po ssibi li ty of ma nuf a cturing t he p a rts, since this is virtua l ly noproblem w ith t he use of mo dern CNC ma chine to ols, but ra t her the perma nent compliance withth e t olera nces aft er the ma nuf a cturing pro cess. This a pplies especially to dimen sions in a class ofto lerances w ith very na rrow f ields (< 0.1mm). These can cha ng e immed iat ely a f t er the p a rt ista ken from t he ma chine t ab le d ue t o t he visco-elast ic beha viour o f t he plast ics. In pa rt icular, the

higher level of t herma l expansion, volume cha ng es due t o th e ab sorption of mo isture a s w ell asform and dimensiona l chan ges caused b y the re laxa t ion o f product ion-re la t ed residua l st ressesa re just some o f t he po ssible causes.

Anoth er problem is the f a ct tha t t here is no g enera l sta nda rd for ma chined plas t ic componen ts .The lack o f a common ba sis for ma ter ia l-re la t ed t o lerance for pa r ts such as th is o f t en lead s todisag reement b e tw een t he custo mer and the supplier in reg ard t o t he c lassi f ica t ion o f re jectsa nd/or de fects in delivery. Choo sing a to lerance f ield tha t is suitab le for t he respective ma teria lcan a void d isputes and a lso en sure tha t t he plast ic compo nents function and operat e sa fely as in-te nde d .

The fo l low ing sections of t his chapt er are ba sed o n our ma ny years of experience w ith di f ferent

plast ics an d a re intende d t o a ssist d esign eng ineers in def ining t olerances. The a im is to creat e astand ard ba sis and to avoid un necessary costs cau sed by rejects due to off -spec to leran ces.

The to leran ce f ields tha t w e recommen d can b e a chieved w ith conventiona l production met hod sand w ithout any a ddi t iona l expendi ture . In g enera l, the funct ioning a nd o pera t ing sa fe t y o f t hecomponents w ere not limited because of t he increased tolerance. Narrow er tolerances than thosesta t ed he re are possible to a certa in extent , but w ould necessi ta t e unjusti f iab ly high processingexpenditure, and t he ma teria ls would a lso req uire intermediate treat ment (annea ling) during theprod uction p rocess. If com po nen t pa rts requ ire t olera nce fields of < 0.1mm or ISO series IT9 fitsa nd sma ller, w e w ill be h ap py to a dvise you in the choice o f a technical ly/econo mical ly practica la nd susta inable tolerance field.

2. Plastic-related tolerances

2.1 General tolerances

The g enera l to lerances for unt oleran ced d imension s ca n b e chosen a ccording to DIN ISO 2768 T1,t o lera nce cla ss »m«.In this stand ard , the to leran ces are de fined a s fo llow s:



T o l e r

a n c e s

Ta ble 1: Limiting dime nsions in m m f or line ar me a sures (DIN ISO 2768 T1)

Nominal size range in mmTolerance 0,5 above 3 above 6class up to 3 up to 6

f (fine)

m (med ium) ± 0,2 ± 0,5 ± 1,0

g (roug h)

v (very ro ug h) ± 0,4 ± 1,0 ± 2,0

Nominal size range in mm

Tolerance 0,5 above 3 above 6 above 30 above 120 above 400 above 1000 above 2000class up to 3 up to 6 up to 30 up to 120 up to 400 up to 1000 up to 2000 up to 4000

f (f ine) ± 0,05 ± 0,05 ± 0,1 ± 0,15 ± 0,2 ± 0,3 ± 0,5 -

m (med ium) ± 0,1 ± 0,1 ± 0,2 ± 0,3 ± 0,5 ± 0,8 ± 1,2 ± 2,0

g (ro ug h) ± 0,15 ± 0,2 ± 0,5 ± 0,8 ± 1,2 ± 2,0 ± 3,0 ± 4,0

v (very ro ug h) - ± 0,5 ± 1,0 ± 1,5 ± 2,5 ± 4,0 ± 6,0 ± 8,0

Tab le 2: Limiting dimen sions in m m f or ra dius of curvat ure a nd heig ht of bevel (DIN ISO 2768 T1)

Ta ble 3: Limiting dime nsions in de g rees fo r an g le me asure men ts (DIN ISO 2768 T1)

Nominal size range of the shorter leg in mm

Tolerance up to 10 above 10 above 50 above 120 above 400class up to 50 up to 120 up to 400

f (fine)± 1° ± 30’ ± 20’ ± 10’ ± 5’

m (medium)

g (ro ug h) ± 1° 30’ ± 1° ± 30’ ± 15’ ± 10’

v (very ro ug h) ± 3° ± 2° ± 1° ± 30’ ± 20’

In special cases, fo r lon g itud ina l dimen sion s it is po ssible to cho ose t he t olera nce class »f«.However, it is important tha t permanent compl iance w ith the to lerance in rega rd to componentgeo metry is checked in a greement w ith the manuf acturer.

2.2 Shape and positionThe g ene ral to lerances fo r unt olera nced dimen sion s ca n b e selected a ccord ing t o DIN ISO 2768 T2,t o lera nce cla ss »K«.In t his sta nda rd the tolerances are d ef ined a s follows:

Ta ble 4: Ge ne ral t olera nces fo r straig ht ness an d eve nn ess (DIN ISO 2768 T2)


Tolerance above 10 above 30 above 100 above 300 above 1000class up to 10 up to 30 up to 100 up to 300 up to 1000 up to 3000

H 0,02 0,05 0,1 0,2 0,3 0,4

K 0,05 0,1 0,2 0,4 0,6 0,8L 0,1 0,2 0,4 0,8 1,2 1,6



T o l e r

a n c e s

Dimension category Plastics Comments

A POM, PET, PTFE+ g la ss, PTFE+ bronze, Thermo pla st ics w it h o r

PTFE+ coa l,PC,PVC-U, PVDF, PP-H, or w ith ou t reinf orcem en t/

PEEK, PEI, PSU, HGW (la mina te d fillers

f a bric) (w ith lo w mo isture

absorption)

B PE-HD, PE-HMW, PE-UHMW, PTFE, So f t t hermo pla st ics a nd

PA 6, PA 6 G , PA 66, PA 12 po lya mides w ith

moisture a bsorption

Tab le 5: Gen era l to lera nces fo r recta ng ula rity (DIN ISO 2768 T2)


Tolerance above 100 above 300 above 1000class up to 100 up to 300 up to 1000 up to 3000

H 0,2 0,3 0,4 0,5

K 0,4 0,6 0,8 1,0

L 0,6 1,0 1,5 2,0


Tolerance above 100 above 300 above 1000class up to 100 up to 300 up to 1000 up to 3000

H 0,5

K 0,6 0,8 1,0

L 0,6 1,0 1,5 2,0

Tab le 6: Ge ne ra l to lera nces fo r symme try (DIN ISO 2768 T2)

The g ene ral t olera nce f or run -ou t a nd concent ricity fo r cla ss »K«is 0.2mm.

In special cases fo r shap e a nd po sitio n it is possible t o cho ose t olera nce class »H«. The g en era lto leran ce fo r run-ou t a nd concent ricity fo r cla ss »H«is 0.1mm.How ever, it is importa nt t ha t perma nent complian ce w ith the to leran ce in rega rd to compo nentgeo metry is checked in a greement w ith the manuf acturer.

2.3 Fits

As described a bo ve, it is not possible t o a pply the ISO to lera nce system tha t is usua lly app lied tosteel compo nent s. According ly, th e t oleran ce series IT 01 – 9 shou ld no t be used. In a dd it ion, todet ermine t he correct t olerance series, the processing met hod an d t he t ype of plast ic being usedmust be considered .

2.3.1 Dimensional categories

The d ifferent plastics can b e classified into t w o ca teg ories according t o t heir dimensional stab ility.The se a re sho w n in Ta ble 7.

Tab le 7: Dimension cat eg ories for p lastics



T o l e r

a n c e s

2.3.2 Classification of tolerance series for milled parts

Classification fo r milled pa rts w ith t olerances

Dimensio n A IT10 - 12

ca t eg o ry: B IT11 - 13

Ta ble 8: ISO ba sic to lera nces in µm accord ing to DIN ISO 286

Nominal size ISO tolerance series (IT)rangein mm 6 7 8 9 10 11 12 13 14 15 16

Fro m up to 1-3 6 10 14 25 40 60 100 140 250 400 600

Abo ve up t o 3-6 8 12 18 30 48 75 120 180 300 480 750

Abo ve up t o 6-10 9 15 22 36 58 90 150 220 360 580 900

Abo ve up t o 10-18 11 18 27 43 70 110 180 270 430 700 1100

Abo ve up t o 18-30 13 21 33 52 84 130 210 330 520 840 1300

Abo ve up t o 30-50 16 25 39 62 100 160 250 390 620 1000 1600

Abo ve up t o 50-80 19 30 46 74 120 190 300 460 740 1200 1900

Abo ve up t o 80-120 22 35 54 87 140 220 350 540 870 1400 2200

Abo ve up t o 120-180 25 40 63 100 160 250 400 630 1000 1600 2500

Abo ve up t o 180-250 29 46 72 115 185 290 460 720 1150 1850 2900

Abo ve up t o 250-315 32 52 81 130 210 320 520 810 1300 2100 3200

Abo ve up t o 315-400 36 57 89 140 230 360 570 890 1400 2300 3600

Abo ve up t o 400-500 40 63 97 155 250 400 630 970 1550 2500 4000

2.3.3 Classification of tolerance series for turned parts

Classification f or turned pa rts w ith to lera nces

Dimensio n A IT10 - 11

ca t eg o ry: B IT11 - 12

Ta ble 8: ISO ba sic to lera nces in µm accord ing to DIN ISO 286

Nominal size ISO tolerance series (IT)rangein mm 6 7 8 9 10 11 12 13 14 15 16

Fro m up to 1-3 6 10 14 25 40 60 100 140 250 400 600

Abo ve up t o 3-6 8 12 18 30 48 75 120 180 300 480 750

Abo ve up t o 6-10 9 15 22 36 58 90 150 220 360 580 900

Abo ve up t o 10-18 11 18 27 43 70 110 180 270 430 700 1100

Abo ve up t o 18-30 13 21 33 52 84 130 210 330 520 840 1300

Abo ve up t o 30-50 16 25 39 62 100 160 250 390 620 1000 1600

Abo ve up t o 50-80 19 30 46 74 120 190 300 460 740 1200 1900

Abo ve up t o 80-120 22 35 54 87 140 220 350 540 870 1400 2200

Abo ve up t o 120-180 25 40 63 100 160 250 400 630 1000 1600 2500

Abo ve up t o 180-250 29 46 72 115 185 290 460 720 1150 1850 2900

Abo ve up t o 250-315 32 52 81 130 210 320 520 810 1300 2100 3200Abo ve up t o 315-400 36 57 89 140 230 360 570 890 1400 2300 3600

Abo ve up t o 400-500 40 63 97 155 250 400 630 970 1550 2500 4000



T o l e r

a n c e s

2.4 Surface quality

The d eg ree o f sur face q ua l ity t ha t can be achieved depend s on th e processing metho d. Tab le 9show s the surface qua lit ies tha t can b e a chieved w itho ut a ny ad dit ional expenditure for the indi-vidu a l pro cesses.

Tab le 9: Achievable surfa ce q ua lities for va rious machining processes

Fo rm o f m a ch in in g M a x. a ch ie va b le Ave ra g e r ou g h ne ss Ave ra g e d d e pt h o fdeg ree of ro ug hness va lue Ra (µm) ro ug hness Rz(µm)

Milling N7 1,6 8

Turning N7 1,6 8

Pla ning N8 3,2 12,5

Sa w ing N8 3,2 16

It is possible to a chieve bet ter surface q ua lit ies tha n t hose show n in Tab le 9 in conjunction w ith

highe r production e xpenditure. How ever, the pro duction po ssibilities must be d iscussed w ith th emanufacturer o f the component par t in regard to the respect ive plas t ic and the processingme tho d .

2.5 Tolerances for press fits

2.5.1 Oversize for bushes

To ensure th at friction bea ring bushes sit prope rly in thebea r ing bore , the inser t ion o f a n oversized compo nentha s proved to b e g oo d met hod . The oversize fo rplast ic bushes is very la rg e compa red t o m eta l bea r ingbu shes. How ever, due t o t he visco-elast ic be ha viour o fth e plast ics, this is especia l ly impo rta nt b ecause of th ee f f e c t s o f he a t , a s o the rw ise the b e a r ing b ush w o u ldbecome loo se in th e b ore . If t he m aximum service t em-pera t ure is 50 °C , it i s possible to do w itho ut a n a dd i t i-ona l securing device fo r the b ea ring bush if the o versizesf rom Diag ram 1 a re compl ied w i th . In the case o f tem-pera tures ab ove 50 °C, w e recommen d tha t th e bush bese cure d w i th a de v ice co mmo nly use d in ma ch ine e n-

g ineering (e.g. a reta ining ring according t o DIN 472, seea lso th e cha pt er o n »Friction be a rings«section 2.5).

It should a lso b e considered t hat w hen t he bea ringbush is being inserted , its oversize lea ds to it beingcompressed. Conseq uent ly t he oversize must b econsidered as an excess to the o pera t ing bea r ingp l a y , a nd the in te rna l d i a me te r o f the be a r ingmust be d imensioned accordingly . Diagram 2show s the required b ear ing play in re la t ion to thein terna l d iamet er o f t he be ar ing . To prevent t hebea ring from sticking a t temperat ures ab ove 50° C,

i t i s necessary to correct th e b ear ing play by th efa ctors sho w n in th e cha pte r on »Frictionbe a rings«section 2.3.

0,007

0,006

0,005

0,004

0,003

0,002

0,001

20 40 60 80 100 120 140 160 1800

Outer diameter of the fric tion bea ring in mm

P r e s s - f i t o v e r s i z e p e r m m o u t e r d i a m e t e r i n m m

Diag ram 1:Press-fit o versize fo r friction bea rings

0 10 30 50 100 150 200

0,1

1,0

0,9

0,8

0,7

0,6

0,5

0,4

0,3

0,2

0

Internal diameter of bearing in mm

O p e r a t i n g b e a r i n g p l a y i n %

Diagram 2: Operating b earing play



T o l e r

a n c e s

In rega rd to d imensioning t h in w a l ledbearing bushes, rings and similarco mpo ne n ts, it mus t be no te d tha t themeasuring forces tha t a re appl ied andthe de f o rma t io n tha t th i s ca use s ca n

result in incorrect measurements.Hence , the to lerances for the outerdiameter and wa l l th ickness shown inFigure1 are recomm end ed.

2.5.2 Press-fit undersize for antifriction bearings

Anti f r ic t ion bea r ing s can be inserted d i rect ly in to the undersized bea r ing sea t f or ma ximumoperating temperat ures of up to 50° C. If low stress and low operating temperat ures are expected,

no a dd it iona l security is required fo r the bea ring , but t his is, how ever, recommen ded fo r high erstresses a nd o pera ting t empe rat ures. Ag a in this is beca use of t he visco-elast ic be ha viour of th eplast ics w hich can result in a red uction in the comp ression fo rce a nd b ea ring migra tion . Thebear ing can a lso be securedwi th dev ices commonly usedin machine eng ineering (e.g . re-ta in ing r ing according to DIN472). If t he b ea ring is to be usedin a reas w here h igh t empera tu-res or loa ds are e xpected , it is al-so possible to place a steel slee-ve in the b ea ring bo re. This steel

sleeve is f ixed in the bearingbore wi th addi t iona l securingelements , and the bear ing i spressed in t o t his ring.

Diagram 3 shows the requiredtem perat ure-rela t ed und ersizesfor f ix ing the bear ing in thebea ring sea t b y compression.

For bea ring sea ts into w hich an -t i f rict ion bea r ings a re inser ted f or opera t ion a t normal tempera ture a nd loa d condi t ions, w e re-commend the fo llow ing press-fit und ersizes an d t olerances:

Bearing seat diameter up t o 50 mm c – 0.15 /– 0.25 mmBearing seat diame ter a bo ve 50 up to 120 mm c – 0.25 /– 0.35 mm

Bearing seat diameter a bove 120 mm c – 0.40 /– 0.50 mm

In o ur many years o f experience , bear ing sea t s manufa ctured a ccording t o t he a bove exhibi t noexcessive de crea se in com pression fo rce a nd a re ab le to keep t he a ntifriction b ea ring s in positionsafe ly a nd securely.

How ever, if th is recomm enda tion is ta ken, it should be n ot ed t ha t in the ca se of extremely sma llra t ios be tw een the bea r ing sea t d iameter and the o uter d iameter it i s possible tha t the b ear ingsloosen de spite compliance w ith o ur recommenda tions. This can be a t t ribut ed t o t he fa ct tha t t he

stresses caused b y insert ion can result in elong a tion o f t he residua l mat eria l . As a result o f t his,the b ear ing sea t d iamet er becomes la rg er and the compression f orce neede d t o f ix the bea r ingcan no long er be ma inta ined. This beh a viour is exacerba ted by high t empe rat ures a nd/or flexingtha t o ccurs dur ing o pe ra t io n . Th i s ca n be ne g a te d to a ce rt a in e x te n t by t he se cur ingmea sures de scribe d ab ove.

70 0-0,2

2 , 5

- 0 , 1 0

- 0 , 1 5

Ø 4 5

( Ø 4 0 )

+ 0 , 2 5

+ 0 , 1 5

Figure 1 : Example o f to lerance for abea ring bush

0,1

0,7

0,6

0,5

0,4

0,3

0,2

0,020 40 60 80 100 120

O p e r a

t i n g t e m

p e r a t

u r e 5 0

° C

O p e r a t i ng t e

m p e r a t u r e 2

0 ° C

Antifriction bearing diameter in (mm)

B o r e s e t t i n g s i z e i n m m

Diag ram 3: Bore sett ing sizes for bea ring seat s



T o l e r

a n c e s

3. General information

The b asic to lerances an d d imensions sta ted ab ove can o nly be susta inably mainta ined unde rno rma l climat ic con dition s (23° C/50% rel. humidity). If th e e nviron men ta l cond itions diff er, t heymust be considered b y apply ing the respect ive correct ion f a c tors. These can b e f ound for t hespecific ca ses in th e pre viou s cha pt ers.

3.1 Dimensional and volume changes under the influence of temperature

In g eneral i t can be sa id t ha t elong at ion caused b y tempera ture is approx. 0.1% per 10 K tempe -rature chang e. In a ddit ion, in the case of polyamides, due t o t he a bsorption o f moisture a chan gein volume o f 0.15 – 0.20% per 1% w a te r ab sorbed must b e considered .

Considering t he m at eria l-specif ic coef f icient of elonga tion, the expected elonga tion a nd volumechanges due to f luctua ting temperat ures can b e calcula t ed approximat ely.

Hence, the expected elong at ion is

Dl = I . a . (u1 – u2) [mm]

whe reDI = e xp ect e d elo n g a t io nl = o rig in al le ng t h in mma = ma terial-specific coefficient of elong at ionu1 = insta lla t ion t emperature in °Cu2 = opera t ing t empera ture in ° C

The expected chang e in vo lume is ca lcula t ed – w i th the a ssumption t ha t t he e long a t ion is no thindered in a ny direction – from:

DV = V . b . (u2 – u1) [mm 3]

a nd

b = 3 . a

whe reDV = expected chang e in volumeV = o rig in a l vo lu me in m m3

a = ma terial-specific coefficient of elong at ionb = ma terial-specific coef ficient of volume expan sion

u1 = insta lla t ion t emperature in °Cu2 = opera t ing t empera ture in ° C

The m a te ria l-specific coe fficient s of elong a tion can b e fo und in Ta ble 10.



T o l e r

a n c e s

Material Abbreviation Coefficient of elongationa 10-5 . K-1

Po lya mide 6 ca st PA 6 G 7

Po lya mide 6 ca st CC PA 6 G-CC 8

Oila mid PA 6 G + Öl 7

Ca la umid 612 PA 6/12 G 8

Ca la umid 1200 PA 12 G 10

Po lya mide 6 PA 6 9

Po lya mide 6 + 30% g la ss f ib re PA 6 GF30 3



Po lya cet a l POM -C 10

Po lya cet a l GF-f illed POM -C-GF30 2,5

Po lyet hylene t erepht ha la te PET 7

Po lyet hylene t erepht ha la te + lubrica nt a d d it ive PET-GL 8

Po lyt et ra f luo ro et hylene PTFE 19

Po lyt et ra f luo ro et hylene + 25% g la ss f ib re PTFE -GF25 13

Po lyt et ra f luo ro et hylene + 25% co a l PTFE -K25 11

Po lyt et ra f luo ro et hylene + 40% bro nze PTFE -B40 10

Po lyet hylene 500 PE-HMW 18

Po lyet hylene 1000 PE-UHMW 18

Po lyet heret herket o ne PEEK 4

Po lyet heret herket o ne mo d if ied PEEK-GL 3

Po lysulpho ne PSU 6

Po lyet her imid e PEI 6

Tab le 10: Linear coe fficients of e long at ion o f various plastics

3.2 Geometric shapes

The g eome tr ic re la t ionships o f a w orkpiece can cause chang es in d imensions and sha pe a f t erthe ma chining process. Therefore , e i ther the g eomet r ic sha pe ha s to b e chang ed o r the recom-mend ed to leran ce series for w orkpieces w ith extreme g eome tric sha pe a nd w all thickness rela t i-onships, e.g. e xtreme o ne-sided ma chining, e xtremely thin w a lls, extreme w a ll thickness differen-ces, must b e a da pted according ly. If t here is an y uncerta inty in rega rd to the def init ion o f shape,

dimension o r position t olerances, w e w ould be plea sed t o a ssist.

3.3 Measuring technology

It is very di f f icult t o m ea sure narrow to lerances in plast ic w orkpieces, especia l ly in t hin-w alledpa rts. The pressure exerted o n th e w orkpiece by the mea suring instrumen t can def orm t he plasticpar t , or the low coef f icient o f f r ict ion o f p last ics can disto r t the s ta r t ing to rque o f micromet erg a ug es. This inevita bly lea ds to incorrect mea sured values. Theref ore i t is recomme nd ed t ha tconta ctless measuring system s are used.



Machining guidelines



M a c h

i n i n g g u i d e

l i n e s

Machining guidelines

1. Machining of thermoplastics

With th e increa sing variety o f en g ineering plast ics an dthe resul t ing appl ica t ions , design eng ineers now ha ve

ma ny new horizons tha t w ere previously unth inkab lew ith conventiona l mat eria ls. In ma ny cases, in ad dit ionto ma ter ia l limita t ions , the only o th er limit t o d esignpossibi l it ies are t he restrict ions imposed b y the ma nu-fa cturing process. Part icularly i f larg e volume pa rts arereq uired f rom cast polyam ides an d po lya ceta l (POM) orpolyet hylene tereph th a la t e (PET), ma nuf a cturingprocesses such as injection m oulding cann ot be used .This a pplies eq ua lly to co mplex parts th a t req uirema chining from a ll sides w ith narrow to leran ces.

In th is a rea , machining has proven to be the best

met hod . Highly precise part s an d large comp one nts canbe ma nuf a ctured especia l ly econ om ica l ly in sma ll a ndmedium ba tches by machining.

For the ma nufa cture o f h igh q ua l i ty prod ucts, cer ta inspecif ic fea t ures o f p last ics must be considered w henmachines and t ools are b eing chosen and used.

1.1 Machining equipment/tools

No special ma chines or pro cesses are required fo r ma chining. The ma chines th at are norma lly used

in the w oo dw orking an d m eta l industries w ith HSS tools (high perfo rmance superspeed steel) orha rd met al to ols can b e used. The o nly thing to consider is that w hen a circular saw is used to cutplastic, ha rd met allic sa w blad es must b e used.

The g roup of g lass fibre reinf orced plastics is a specia l ca se. While it is po ssible to ma chine th emw ith ha rd met al t oo ls, it is very difficult to achieve economic results due t o t he short service life ofth e to ols. In th is case it is a dvisab le to use diam on d t ipped t oo ls, w hich a re much more expensivetha n conventiona l to ols but ha ve a much long er service life.

1.2 Machining and clamping the workpiece

Plas t ics have low er therma l cond uctance propert ies than meta ls, a s w el l a s a low er mod ulusof e las t ic ity . If no t ha ndled properly, the w orkpiece can become extremely w arm a nd t hermalexpansion can occur . High c lamping pressures and blunt too ls cause deformat ion duringmachining. Dimensiona l and shape devia t ions outside the tolerance range are t he consequence.

Sa tisfa ctory results a re o nly achieva ble if several ma terial-specific guidelines are considered w henmachining plastics.

In d eta il, the se guidelines are:• The highest possible cutt ing speed should be chosen.• Optimum chip removal must b e ensured so tha t t he chips are no t d raw n in by the t ool .• The t oo ls th a t a re used must be very sha rp. Blunt t oo ls can cau se extrem e hea t, w hich results in

defo rmation and thermal expansion.• The c lamping pressures must n ot be too h igh a s th is wo uld result in d e forma t ion o f t he w ork-

piece and the clamping to ol w ould leave marks in the w orkpiece.• Be ca use o f t he l o w de g re e o f s t i ff ne ss, the w o rkp ie ce must b e a de q ua te l y suppo r te d o n the

ma chine t a ble an d should lie a s flat as possible.

Fig. 1: Complex compon ent mad e from POM

115



• Per fect , h igh-qua l i ty surfaces can only be obta ined when the machines opera te wi th lowvibration.

If t hese gu idelines are complied w ith, i t is possible t o o bt a in na rrow, plast ic-oriented to lera ncesw ith a high level of reproducibility w ithout difficulty.

1.3 Cooling during machining

As a rule it is no t a bsolute ly necessa ry to coo l th e w orkpiece during m a chining. If coo ling is to bea pplied it is recommend ed t ha t compressed a ir is used. This ha s th e ad vant a ge t ha t in ad dition tothe co o l ing e f f e ct , the ch ips a re re mo ve d f ro m t he w o rking a re a a nd ca nno t be d ra w n in to thew orkpiece or to ol.

Conventiona l drilling emu lsions can a lso b e used fo r coo ling an d a re especially recom mend ed f ordeep b ores and cutt ing threa ds. In a dd it ion, i t is possible to achieve higher ra t es of fo rwa rd feeda nd conseq uent ly, short er running times.

How ever, if using d rilling emulsion s, at ten tion should be pa id tha t t hese are completely remo veda ft er ma chining. This prevents o ily compo nent s cau sing prob lems in subseq uent processes such a sbo nding o r pa in t ing , especia lly in the case o f po lyamides whe re the w a t er in the emulsion cancause chang es in th e components throug h a bsorption.

2. Parameters for the individual machining processes

2.1 Sawing

Plas t ics can be saw n w i th a b and saw or a c i rcula r saw. The choice depen ds on the sha pe o f t hesemi-f in ished product . The use o f a ba nd saw is par t icula r ly recommend ed w hen a “ supportgroo ve” (prism) is used t o cut rods and tube s and a lso ha s the a dvant ag e tha t the b uilt up hea t isdissipat ed via t he long saw blade. How ever, the teet h of t he blade must be set ad eq uat ely so th atthe blade cannot jam.

Circula r saw s, on th e o t her han d, a re mainly used f or cut t ing sheets and b locks w ith s t ra ightedg es. Here , a t tent ion should be pa id th a t the fee d ra t e is ad eq ua t e so th a t chips a re removed,tha t the sa w b l a de do e s no t j a m a nd tha t the p l a st i c do e s no t o v e rhe a t a t the po in t w he re it i sbeing cut. Tab le 1 conta ins guiding values fo r the cutting g eom etry of t he saw blad es.

PA, PE, POM, PET, PVDF, PVC

Ba nd sa w Circula r sa w

a = Clea ra nce a ng le (° ) 30 - 40 10 - 15

g = Ef fect ive cut t ing a ng le (° ) 0 - 8 0 - 10

v = Cut t ing speed m/min 200 - 1000 1000 - 3500

t = Number o f t eet h 3 - 5 per inch 24 - 80

t

α

γ

Tab le 1: Too l geo met ry for saw blad es

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M a c h

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2.2 Milling

Mil ling o n convent iona l machining centres i s unproblema t ic. With a h igh cut t ing speed a ndmedium fee d ra t e i t i s possible to achieve h igh levels o f m achining performa nce w i th go odsurfa ce qua lity an d a ccuracy. In rega rd to t he cutte r geo met ry, w e recomm end t he values given in

Ta ble 2.

2.3 Turning on a lathe

Since most plastics prod uce unbro ken chips, it is importa nt t o en sure th a t t he chips a re removed ,as they w ould o therw ise ca tch and revolve wi th the pa r t be ing turned on t he la the . In ad di t ion ,because of th e low deg ree of st if fness of plast ics, there is a g reat d ang er of longer pa rts sag ging,a nd i t is th us ad visable t o use a stea dy rest . The va lues g iven in Ta ble 3 apply to th e cutt ergeometry .

2.4 Drilling

Dril l ho les can b e ma de w ith a conventiona l HSS dri ll . If d eep h oles are being dri lled, i t must beensured t ha t th e chips are removed, as oth erw ise the plast ic on t he w alls of t he hole w ill hea t tothe point o f me lting an d t he d rill w ill “ clog ” . This especially applies to dee p ho les.For d ril led holes in thin-w alled w orkpieces, i t is advisab le to choose a high dri ll ing speed a nd, i fa pplicable, a neut ral (0°) effective cutting an g le. This prevents th e d rill from sticking in t he w ork-piece a nd h inders the a ssocia t ed s t r ipping o f th e hole or the w orkpiece be ing draw n up by the

drill.

Tab le 4 conta ins the recomm end ed values for cutt ing edg e ge ome try.

PA, PE PTFE POM, PET

PVDF, PVC

a = Clea ra nce a ng le (° ) 5 - 15 10 - 15 5 - 10

g = Effe ctive cutting a ngle (°) 0 - 15 15 - 20 0 - 10

v = Cut t ing speed m/min up t o 1000 up to 600 up t o 1000

s2 = Fo rw a rd feed/to o th up t o 0,5 up t o 0,5 up t o 0,5

Ang le o f t w ist in ° 0 - 40 0 - 40 0 - 40

α

γ

PA, PE PTFE POM,PETPVDF, PVC


g = Ef f ect ive cut t ing a ng le (° ) 0 - 10 15 - 20 0 - 5

x = Set t ing a ng le (° ) 0 - 45 0 - 45 0 - 45

v = Cut t ing speed m/min 200 - 500 100 - 300 200 - 500

s = Fo rw a rd f eed mm/rev. 0,05 - 0,5 0,05 - 0,3 0,05 - 0,5

a = Ra te o f cut mm up t o 15 up t o 15 up t o 15

The po int rad ius should be a t lea st 0.5mm

α

γ

χ

a

Tab le 2: Too l ge ome try f or m illing cutte rs

Tab le 3: Too l ge ome try f or la th e chisels



M a c h

i n i n g g u i d e

l i n e s

2.5 Drilling large diameters in sections of round rodWhen d rilling, high t empe rat ures build up o n t he cutt ing ed g es, especia lly w ith highly crysta llinema teria ls such as PA 6 G, w hich canno t b e ad eq uat ely dissipate d be cause of the g oo d insula t ionprope rties of t he plast ics. The hea t causes an interna l expan sion in the m a te ria l , w hich in turncauses com pressive stress in the inside o f t he ro d section. This stress ca n b e so h igh t ha t t he ro dtea rs a nd splits.

This can be a voided to a g reat extent if the ma terial is machined correctly.

It is a dvisa ble to pre-dri ll the ho le and complet e i t w ith a rig ht side t oo l . The pre-dril led h olesshould not exceed 35 mm in diam ete r.

Dril led ho les in long sections of rod must only be ma de f rom on e side, a s otherw ise a n unf avou-rab le s t ress re la t ionship i s crea t ed w hen t he d r il led h oles meet in the midd le o f t he b lank rod ,w hich can lead t o th e rod section cracking.

In extrem e cases it m a y be n ecessary t o h ea t t he b lank to a pprox. 120 – 150° C and pre-dri ll it inthis condit ion. The hole can t hen be completed w hen the rod ha s cooled do w n an d w hen a n eventemperat ure has set in througho ut the b lank.

If t hese ma chining g uidelines a re compl ied w i th , it i s q ui te possible t o m an ufa cture complexproducts f rom eng ineering plas t ics using ma chining processes even w hen the h ighest dema ndsa re placed o n q uality, accuracy and functiona lity.

γ 1

α

ϕ

PA, PE PTFE POM,PETPVDF, PVC


g1 = Ef f ect ive cut t ing a ng le (° ) 3 - 5 3 - 5 3 - 5

J = Po int a ng le (° ) 60 - 90 130 60 - 90

v = Cut t ing speed m/min 50 - 100 100 - 300 50 - 100

s = Fo rw a rd f eed mm/rev. 0,1 - 0,5 0,1 - 0,3 0,1 - 0,3

The a ng le of t w ist o f t he d rill sho uld be a t lea st 12 - 16°

Tab le 4: Too l ge om et ry fo r drills



M e c h

a n i c a l v a l u e s



M e c h


Parameter Condition Footnote

Impa ct re sista nce D IN 53 453 Mea sured w ith an impact pe ndulum t esting ma chine 0.1 DIN 51 222 1

Creep st ress DIN 53 444 St ress t ha t lea ds t o 1% o vera ll expa nsio n a f t er 1,000 h 2

Co eff icien t o f slid ing f rict io n Ha rd en ed a nd gro und a ga in st st eel, P = 0.05 MPa ,

V = 0.6 m/s, t = 60° in vicinit y o f running a rea 3

Linea r co eff icient o f e lo ng a t io n Fo r tempera t ure ra ng e f ro m + 23° C up t o + 60° C 4

Tempera t ure ra ng e Experience va lues, determined o n f inished

parts wi thout load in wa rmed a ir, dependent on t he type

a nd f o rm o f hea t ,

sho rt -term = ma x. 1 h, lo ng -t erm = mo nths 5

Dielect ric st reng th DIN 53 483 a t 106 Hz 6

Co lo urs POM-C na t ura l = w hit e

PET-na tura l = w hite

PVDF-na tura l = w hite to ivory (tra nslucent )

PE-nat ural = w hite

PP-H nat ural = w hite (translucent)

PP-H grey ≈ RAL 7032

PVC-grey ≈ RAL 7011

PEEK-natural ≈ RAL 7032

PSU-nat ural = honey yellow (translucent)

PEI-na tura l = a mber (t ra nslucent ) 7

Unit s a nd a bb revia t io ns o .B. = w it ho ut b rea ka g e

1 MPa = 1 N/mm 2

1 g /cm 3 = 1,000kg /m3

1 kV/mm = 1MV/m no ne

Information and conditions concerning the table“Mechanical values”

The informa tion in the l ist is intend ed t o provide an o verview of t he prope rties of o ur productsand to a l low a q uick comparison of mat eria ls. They represent our present sta nda rd of know ledg ean d do not c la im to b e comple te . Because o f t he h igh level o f d epend ence on env ironment a lin f luences an d processing met hod s, the va lues g iven here should o nly be rega rded as sta nda rdvalues. In no w ay d o t hey represent a lega l ly binding assurance in rega rd to the properties of ourprod ucts nor to t heir suita bi l ity fo r specif ic a pplicat ions. All th e values sta ted here w ere de te r-mined from a verag e values result ing from ma ny individua l mea surement s an d refer to a tem pe-rat ure o f 23°C a nd 50% RH.For speci f ic appl ica t ions , we recomme nd tha t t he suita bi li ty o f t he ma ter ia ls be f i rst t es ted b ypractical experiments.

The cond it ions under w hich th e individua l values w ere de termined , and an y specia l fea tures inrega rd to these values, are conta ined in t he fo llow ing l ist w ith the respective foot not es:



Physical MaterialGuiding Values

D e n s i t y

D I N 5 3 4 7 9

Y i e l d s t r e s s

D I N 5 3 4 5 5

E l o n g a t i o n a t b r e a k

D I N 5 3 4 5 5

M o d u l u s o f e l a s t i c i t y r e s u l t i n g

f r o m t e n s i l e t e s t D I N 5 3 4 5 7

M o d u l u s o f e l a s t i c i t y r e s u l t i n g

f r o m b e n d i n g t e s t D I N 5 3 4 5 7

F l e x u r a l s t r e n g t h

D I N 5 3 4 5 2

I m p a c t s t r e n g t h

D I N 5 3 4 5 3

N o t c h e d - b a r i m p a c t s t r e n g t h

D I N 5 3 4 5 3

B a l l i n d e n t a t i o n h a r d n e s s H 3 5 8 / 3 0

D I N 5 3 4 5 6

C r e e p r a t e s t r e s s a t 1 %

e l o n g a t i o n D I N 5 3 4 4 4 2 )

No . Ma teria l Abbrev. Co lours Test specimen(st a nda rd) cond it io n

1 Polya mide 6 Ca st PA 6 Gna t ura l/b la ck/ dry

b lue humid

2 Po lya mide 6 Ca st + Mo S2 PA 6 G + MoS2 blackdr y

humid

3 Po lya mid 6 Ca st -CC PA 6 G-CC na t ura l/b la ck dry

4Polyamide 6 Cast

PA 6 G-WS bla ckdr y

Hea t st a b ilised humid

5 Oila mid ® PA 6 G + Ölyello w /b la ck/ dry

na t ura l humid

6 Ca la umid ® 612PA 6 /12 G

na tura ldr y

(impa ct resist a nt ) humid

7 Ca la umid ® 1200 PA 12 G na t ura ldr y

humid

8 Po lya mide 6 PA 6 na t ura l/b la ckdr y

humid

9 Polya mide 66 PA 66 na t ura l/b la ckdr y

humid

10 Po lya mide 6 + Gla ss f ib re PA 6 + GF 30 b la ckdr y

humid

11 Po lya mid 66 + Gla ss f ib re PA 66 + GF 30 b la ckdr y

humid

12 Po lya mide 12 PA 12 na t ura l d ry

13Polyaceta l

POM - C na tura l7)/bla ck dryCopolymer

14Polyaceta l

POM - C GF 30 b la ck dryCopolymer + Glass fibre

15Polyethylen-

PET na tura l7) dr yterephtala t

16Polyethylenterephtala t/

PET-GL lig htg rey drylubricant additive

17Polytetra f luoro-

PTFE w hite dryethylen

18Po lyt et ra f luo ro - PTFE + 25%

g rey dryet hylen /Gla ss f ib re Gla ss f ibre


bla ck dryet hylen /Ca rbon Ca rbo n


bro w n dryet hylen /Bra ss Bra ss

21Polyvinyl-

PVDF na tura l7) dr ydifluorid

22 Po lyet hylene 300 PE - HDna tura l7)

dr yblack

23 Po lyet hylene 500 PE - HMWna tura l7)

dr ybla ck/gre en

24 Po lyet hylene 1000 PE - UHMWna tura l7)

dr ybla ck/gre en

25 Polypro pylene PP - H na t ura l7)/g re y7) dr y

26 Po lyvinylchloride PVC - Ugrey7)/bl a ck/

dr yred/w hite

27 Polyca rbo na t e PC t ra nspa rent d ry

28Polyether-

PEEKna tura l7)

dr yket o ne b la ck

29Polyetherketone

PEEK - GL b la ck dry(modified)

30 Po lysulfo ne PSU na tura l7) dr y

31 Po lyether a mide PEI na tura l7) dr y

1 2 3 4 5 6 7 8 9 10 r j zS ezR Et EB3 j bB a cU a cN HK j 1/1000

g /cm3

MPa % MPa MPa MPa kJ/m2

kJ/m2

MPa MPa

1,1580 40 3.100 3.400 140

o. B. 1 4 160

1 760 100 1.800 2.000 60 1 15 125

1,1585 40 3.100 3.300 130

o. B. 1 5 150

1 760 100 1.800 2.000 50 1 15 115

1,15 71 1 40 2.800 2.700 97 o. B. - 125 -

1,1590 30 2.500 3.000 120

o. B. 1 4 170

1 760 80 2.000 2.300 40 1 12 130

1,1480 50 2.500 2.800 135

o. B. 1 5 140

1 755 120 1.500 1.800 55 1 15 100

1,1280 55 2.500 2.800 135

o. B. 1 12 140

1 1555 120 1.500 1.800 55 o . B. 100

1,0360 55 2.200 2.400 90

o. B. 1 15-

1 1150 120 1.800 - - 100

1,1470 50 2.700 2.500 130

o. B. 1 3 160

1 845 180 1.800 1.400 40 o . B. 70

1,1485 30 3.000 2.900 135

o. B. 1 3 170

1 865 150 1.900 1.200 60 1 15 100

1,40180 4 9.000 8.300 240

556 220

35120 7 6.400 4.800 40 15 150

1,29 160 5 11.000 - - 50 6 240 40

1,02 50 1 200 1.800 1.500 60 o. B. 1 15 100 1 4

1,41 65 40 3.000 2.900 115 o. B. 1 10 150 13

1,59 125 3 9.300 9.000 150 30 5 210 40

1,38 80 40 3.000 2.600 125 o. B. 1 4 140 13

1,43 75 5 2.200 - - 30 2 - -

2,18 25 380 750 540 6 o. B. 16 30 1,5

2,23 15 280 1.500 1.320 4 o. B. 12 31 -

2,12 15 180 - 1.275 9 - 8 38 -

3,74 14 140 1.400 1.375 8 - 11 39 -

1,78 56 22 2.000 2.000 75 o. B. 1 15 120 3

0,95 22 300 800 800 32 o. B. 12 40 3

0,95 28 300 850 850 40 o. B. 50 45 3

0,94 22 350 800 800 27 o. B. o . B. 40 -

0,91 32 70 1.400 1.400 45 o. B. 7 70 4

1,42 58 15 3.000 - 82 o. B. 4 130 -

1,20 60 80 2.300 2.200 95 o. B. 1 25 100 40

1,32 95 45 3.600 4.100 160 o. B. 7 230 -

1,48 118 3 8.100 10.000 210 25 2,5 270 -

1,24 75 1 50 2.500 2.700 106 o. B. 4 150 22

1,27 105 1 50 3.100 3.300 145 o. B. - 165 -

All listed values were ob ta ined as averag e values from a multitu de of individual mea sures, and a re related t o a t empera ture of 23 °C and 50% RF.

Mechanical values

As of 9/2004



Slidingfrictioncoefficient

a g a i n i s t s t e e l 3 )

S l i d i n g w e a r a g a i n s t

s t e e l ( d r y r u n n i n g ) 3 )

M e l t i n g t e m p e r a t u r e

D I N 5 3 7 3 6

T h e r m a l c o n d u c t i v i t y

D I N 5 2 6 1 2

S p e c i f i c t h e r m a l c a p a c i t y

C o e f f i c i e n t o f l i n e a r

e x p a n s i o n 4 )

O p e r a t i n g t e m p e r a t u r e r a n g e ,

l o n g - t e r m 5 )

O p e r a t i n g t e m p e r a t u r e r a n g e ,

s h o r t - t e r m 5 )

F i r e b e h a v i o u r a f t e r U L

D i e l e c t r i c c o n s t a n t 6 )

D I N 5 3 4 8 3

D i e l e c t r i c l o s s f a c t o r 6 )

D I N 5 3 4 8 3

S p e c i f i c v o l u m e r e s i s t a n c e

D I N 5 3 4 8 2

S u r f a c e r e s i s t a n c e

D I N 5 3 4 8 2

D i e l e c t r i c s t r e n g t h

D I N 5 3 4 8 1

C r e e p c u r r e n t r e s i s t a n c e

D I N 5 3 4 8 0

M o i s t u r e a b s o r p t i o n i n n a t u r a l

r u b b e r u n t i l s a t u r a t e d D I N 5 3 7 1 5

W a t e r a b s o r p t i o n u n t i l

s a t u r a t e d D I N 5 3 4 9 5

11 12 13 14 15m V Tm l c

- mm/km ° C W/(K·m) J/(g ·K)

,360,10 + 220 0,23 1,7,42

,320,10 + 220 0,23 1,7

,37

,36- + 220 0,23 1,7,42

,360,10 + 220 0,23 1,7

,42

,180,05 + 220 0,23 1,7,23

,360,12 + 220 0,23 1,7

,42

,40 - + 190 0,23 1,7

,380,23 + 218 0,23 1,7

,42

,350,10 + 265 0,23 1,7

,42

,46- + 220 0,25 1,5

,52

,45 - + 255 0,30 1,5

,320,80 + 178 0,30 2,09

,38

,32 8,90 + 168 0,31 1,45

,50 - + 168 0,40 1,21

,25 0,35 + 255 0,24 1,1

,20 0,10 + 255 0,23 -

,08 21,0 + 327 0,23 1

,14 1,30 + 327 0,41 -

,12 1,0 + 327 0,70 -

,14 0,50 + 327 0,70 -

,30 - + 178 0,19 0,96

,29 7,4 + 128 0,38 1,86

,29 1,0 + 133 0,38 1,88

,29 0,45 + 133 0,38 1,84

,35 11,0 + 162 0,22 1,7

,60 56,0 - 0,159 1,05

,55 22,0 + 230 0,21 1,17

,34 - + 340 0,25 1,06

,11 - + 340 0,24 -

,40 - - 0,26 1

- - - 0,22 -

16 17 18 19 20 21 22 23 24 25 26 27 28a - - - eR t a n d rD Ro Ed - w (H2O) WS -

10-5

·K-1

° C ° C - - - Ω· cm Ω kV/mm - % %

7 - 8- 40

+ 170 HB 3,7 0,031015 1013 50 KA 3c

2,2 6,5hard, pressure and abrasion resistant

+ 105 1012 1012 20 KA 3b can be produced in largest dimensions

7 - 8- 40

+ 160 HB 3,7 0,031015 1013 50 KA 3c

2,2 6,5as PA 6 G, except

+ 105 1012 1012 20 KA 3b increased cristallinity

8 - 9- 40

+ 150 HB 3,7 0,031015 1013 50 KA 3c

2,5 7,5 higher impact strength than PA 6 G+ 90 1012 1012 20 KA 3b

7 - 8- 40

+ 180 HB 3,7 0,031015 1013 50 KA 3c

2,2 7as PA 6 G, except heat

+ 105 1012 1012 20 KA 3b ageing resistant

7 - 8- 40

+ 160 HB 3,7 0,031015 1013 50 KA 3c

1,8 5,5 highest abrasion resistance,

+ 105 1012 1012 20 KA 3b low sliding friction

7 - 8- 40

+ 160 HB 3,7 0,031015 1013 50 KA 3c

2,2 7as PA 6G, except set for

+ 105 1012 1012 20 KA 3b high impact strength

10 - 11- 60

+ 150 HB 3,7 0,031015 1013 50 KA 3c

0,9 1,4low water absorption, very good

+ 110 1012 1012 20 KA 3b long-term rupture strength

8 - 9-30

+ 140 HB3,7 0,031 1015 1013 50 KA 3c

3,0 10,0tough, good

+ 100 7 0,3 1012 1010 20 KA 3b vibration damping

9 - 10- 30

+ 150 HB3,2 0,025 1015 1012 50 KA 3b

2,5 9,0high abrasion resistance

+ 100 5,0 0,2 1012 1010 20 CTI 600 (similar to PA 6 G)

2 - 3- 30

+ 180 HB3,7 0,021 1015 1014 60 KA 3c

2,1 6,3high strength, low

+ 120 7,0 0,2 1013 1012 30 KA 3a thermal expansion

2 - 3- 30

+ 180 HB 3,7 0,02 1014 1013 60 CTI 475 1,7 5,5high strength, low

+ 120 thermal expansion

11 - 12- 70

+ 140 HB3,1 0,03

2 x 1015 1013 30KA 3b

0,8 1,5tough, hydrolysis resistance

+ 70 3,6 0,06 CTI 600 negligible moisture absorption

9 - 10- 30

+ 140 HB 3,9 0,003 1015 1013 70KA 3c

0,2 0,8high strength,impact resistance

+ 100 KC1 600 low creep behaviour

3 - 4- 30

+ 140 HB 4,8 0,005 1015 1013 65KA 3c

0,17 0,6high strength,

+ 110 KC1 600 low thermal expansion

7 - 8- 20

+ 160 HB 3,6 0,008 1016 1014 60 KC 350 0,25 0,5tough, hard, negligible cold flow,

+ 100 dimensionally stable

7 - 8- 20

+ 160 HB 3,6 0,008 1016 1014 - - 0,2 0,4as PET, plus highest

+ 110 wear resistance

18 - 20- 200

+ 280 V - 0 2,1 0,0005 1018 1017 40KA 3c

!0,01 !0,01high chemical resistance,

+ 260 KB1 600 low strength

12 - 13- 200

+ 280 V - 0 2,85 0,0028 1016 1016 13 - !0,01 !0,01as PTFE,except

+ 260 higher strength

10 - 11- 200

+ 280 V - 0 - - 103 103 2,8 - !0,01 !0,01as PTFE,except

+ 260 lower wear due to sliding friction

9 - 10- 200

+ 280 V - 0 - - 108 108 - - !0,01 !0,01higher strength than PTFE,

+ 260 but chemically less resistant

13- 40

+ 160 V - 0 8,0 0,165 5 x 1014 1013 25 CTI 600 !0,04 !0,04resistant to UV-, b- and

+ 140 g-Radiation, resistant to abrasion

18- 50

+ 80 HB 2,4 0,004 1 1016 1014 47 KA 3c !0,01 !0,01high chemical resistance

+ 50 low density, high abrasion

18- 100

+ 80 HB 2,9 0,0002 1 1016 1014 44KA 3c

!0,01 !0,01as PE-HD,but far more

+ 50 KC1 600 abrasion resistant

18- 260

+ 80 HB 3,0 0,0004 1 1016 1014 44KA 3c

!0,01 !0,01as PE-HMW,but more abrasion

+ 50 KC1 600 resistant at low friction values

160

+ 100 HB 2,25 0,00033 1 1016 1014 52 KA 3c !0,01 !0,01as PE-HD,but higher

+ 80 thermal strength

80

+ 70 V - 0 3,3 0,025 1016 1013 39 KA 3b !0,01 !0,01good chemical resistance

+ 50 hard and brittle

6 - 7- 40

+ 140 V - 2 3,0 0,006 1017 1015 32 KA 1 0,20 0,36transparent,impact resistance,

+ 110 low cold flow

4 - 5-40

+ 310 V - 0 3,2 0,002 1016 1016 24 CTI 150 0,20 0,45high temperature resistance,hydrolisis

+ 250 dimensionally stable

3-40

+ 310 V - 0 - - 105 - 24,5 - 0,14 0,3as PEEK, except higher pv-values

+ 250 better sliding properties

5 - 6- 40

+ 180 V - 0 3,0 0,002 1017 1017 30KA 1

0,40 0,80can be sterilised in steam

+ 160 CTI 150 hydrolisis resistant,radiation resistant

5 - 6-40

+ 200 V - 0 3,0 0,003 1018 1017 33 CTI 175 0,75 1,35high strength and rigidity

+ 170 high thermal resistance

Specific prope rties

Thermal values Electrical values Miscellaneous data

All ca lcula tions, designs and technical specif ica tions are me rely for informa tion a nd a dvice. Legally binding a ssurances of pro perties and/or results cannot be t aken f rom t his informa tion. We recom-mend carrying out practica l tests to establish the suitabili ty of a product for a given application. Subject to errors and changes!



M e c h


PA 6 G

PA 12 G

Oilamid

PA 6

PA 66PA 12

POM - C

PET

PET - GL

PE - HMW

PE - UHMW

PTFE

PEEK

Steel St. 37

Stainless steel 1.4301

Stainless steel 1.4571

Brass

PA 6 G

PA 12 G

Oilamid

PA 6

PA 66

PA 12

POM - C

PET

PET - GL

PE - HMW

PE - UHMW

PTFE

PEEK

Comparison of material costs (volume prices)

E-modulus from tensile test in MPa (short-term value)

Permissible yield stress in MPa (short-term value)

0 500 1000 1500 2000 2500 3000 3500 4000

PA 6 G

PA 12 G

Oilamid

PA 6

PA 66

PA 12

POM - C

PET

PET - GL

PE - HMW

PE - UHMW

PTFE

PEEK0 10 20 30 40 50 60 70 80 90 100

3600

750

850

800

2200

3000

3000

1800

3000

2700

2500

2200

3100

95

25

22

28

75

80

65

50

85

70

80

60

80



M e c h


Flexural strength in MPa (short-term value)

PA 6 G

PA 12 G

Oilamid

PA 6PA 66

PA 12

POM - C

PET

PET - GL

PE - HMW

PE - UHMW

PTFE

PEEK0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170

Long term service temperature in °C (in air w ithou t sta tic stress)

PA 6 G

PA 12 G

Oilamid

PA 6

PA 66

PA 12

POM - C

PET

PET - GL

PE - HMW

PE - UHMW

PTFE

PEEK0 25 50 75 100 125 150 175 200 225 250 275

Coefficient of sliding friction against steel(harden ed a nd g round , P = 0,05 MPa, v = 0,6 m/s, t = 60 ° C (in the vicinity of th e running surface)

PA 6 G

PA 12 G

Oilamid

PA 6

PA 66

PA 12

POM - CPET

PET - GL

PE - HMW

PE - UHMW

PTFE

PEEK0 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40 0,45

160

6

27

40

115

125

115

60

135

130

140

90

140

0,34

0,08

0,29

0,29

0,2

0,25

0,32

0,32

0,35

0,38

0,18

0,4

0,36

250

260

80

80

110

100

100

70

100

100

105

110

105



M e c h


Coefficient of linear expansion

PA 6 G

PA 12 G

Oilamid

PA 6PA 66

PA 12

POM - C

PET

PET - GL

PE - HMW

PE - UHMW

PTFE

PEEK0 1 2 3 4 5 6 7 8 9 10 11 12 13 18 19

(10-5 · K-1)

pv guiding values in MPa · m/s (dry running w ith inte gra te d lubrication v = 0,1 m/s)

PA 6 G

PA 12 G

Oilamid

PA 6

PA 66

PA 12

POM - CPET

PET - GL

PE - HMW

PE - UHMW

PTFE

PEEK0 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40

Water absorption until saturated in %

PA 6 G

PA 12 G

Oilamid

PA 6

PA 66

PA 12

POM - C

PET

PET - GL

PE - HMW

PE - UHMW

PTFE

PEEK0 1 2 3 4 5 6 7 8 9 10 11

19

18

18

4

8

7

10

10

9

7

10

7

12

0,34

0,05

0,08

0,08

0,25

0,15

0,15

0,08

0,13

0,11

0,23

0,13

0,45

<0,01

<0,01

<0,01

0,4

0,5

0,8

1,5

9

10

7

6,5

1,4

0,10



C h e m

i c a l r e s i s t a n c e

Information on how to use the list“Chemical resistance”

The info rma tion reg a rding chem ica l resistan ce in the f ol low ing l ist rela te s to experimen ts inw hich th e samples were subjected to the respective med ia free o f externa l stress an d loa ding. Thisis suppleme nt ed by o ur practica l experience a nd , in mo st cases, ma ny yea rs of using plast ics incontact w ith t hese media . Due to the variety of med ia , th is list is just a n excerpt of the d at a t hat isa v a i la b le to us. If t he l ist d o e s no t co n ta in the me d ium tha t y o u use , w e w o u ld be ha ppy toprovide info rmat ion on t he resista nce of o ur plastics on req uest.

When using t he list, plea se remember t ha t f a ctors such as:

• devia t ing deg rees of purity of the m edium• devia t ing concentra t ion of the med ium

• temperat ures di f ferent to t hose sta ted• f luctua ting temperat ures• mechanical stress• pa rt g eom etries, especially tho se th a t lead to thin w alls or extreme differences in w all thickness• stresses that are creat ed b y machining• mixtures tha t a re made up of d if ferent med ia• combinat ions of the ab ove factors

can ha ve an eff ect on t he chemical resista nce.

Neverthe less, in spite o f b eing ra t ed a s a compo nen t w ith »limited resistan ce«, a p last iccomponent can st ill be superior to a me ta l part a nd can a lso b e more practica l f rom a n economic

aspect.

In t he ca se of o xidising ma terials such as nitric acid a nd pola r org an ic solvents, despite a chemica lresistan ce ag ainst th e med ium, in ma ny the rmoplastics the re is st il l a d a ng er of stress cracking .Therefore fo r the ma nufa cture of pa rts tha t come into cont act w ith such media , a process shouldbe cho sen tha t creat es as little mecha nical stress as possible in th e w orkpiece. An a lterna tive is todecrease the stress by an nea ling t he semi-finished pro ducts befo re and d uring t he ma nufa cturingprocess.

Genera l ly i t is not possible to forecast t he level of resista nce ag ainst mixtures of di f ferent media ,even if the plastic is resistant to the individual compon ent s of t he mixture.Therefo re in such a ca se w e recomm end t ha t t he ma teria l is sto red a nd a ge d w ith t he respective

mixed medium unde r the expected env ironmenta l cond i t ions . It i s a l so importa nt to remembertha t w here par ts a re to be subjected to tw o or more media t here could be an a ddi t iona l tempe-rature loa d in the area o f immediat e contact due t o th e evolving reaction heat .

In spite of th e ra t ing »resistan t«, in certa in ca ses th e surfaces of plast ics can b ecome ma tt e o rdisco loured, and t ransparent p las t ics can become opa que w hen they come in to conta ct w ith t hemed ia. How ever, the resista nce remains intact even a ft er these surface chang es.

The in forma t ion conta ined in the l ists correspond s to our present sta nda rd o f know ledge a ndshould be regarded as s tandard va lues . I f in doubt , or in the case o f speci f ic appl ica t ions ,w e recommend tha t the mat eria l be ag ed unde r the expected en vironmenta l condit ions to t est i tsresistance.



Chemical resistance

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

1 Acet a l a ldehyd e 40 20 + + + + + + + + + + + + + + +

2 Acet a mid e 50 20 + + + + + + + + + + + + / / +

3 Acet one UV RT + + + + + + + + + + + + o o +

4 Acrylnit rile UV RT + + + + + + + + + + / / / / +

5 Alkyl a lko ho l UV RT o o o o o o o o o o / / + + +

6 Aluminium chlo ride 10 RT + + + + + + + + + + o o + + +

7 Fo rmic a cid 2 RT o o o o o o o o o o + + + + +

8 Fo rmic a cid UV RT L L L L o L L L L o - - o o +

9 Ammo nia 10 RT + + + + + + + + + + + + - - +

10 Ammo nium hydroxide 30 RT + + + + + + + + + + - - - - +

11 Ammo niumnit ra t e UV RT + + + + + + + + + + + + + + +

12 Aniline UV RT - - - - o - - - - o o o + + +

13 Ano ne 100 20 + + + + + + + + + + + / / / +

14 Ant imo nt richlo ride 10 RT - - - - - - - - - - / / / / +

15 Benza ldehyd e UV RT o o o o o o o o o o + + + + +

16 Pet ro l, no rma l HÜ 40 + + + + + + + + + + + + + + +

17 Pet ro l, super HÜ 40 + + + + + + + + + + + + / / +

18 Benzene UV RT + + + + + + + + + + o o + + +

19 Benzene a cid UV RT - - - - + - - - - + o o + + +

20 Benzyl a lco ho l UV RT o o o o o o o o o o + + + + +

21 Blea ching lye (12,5% AC) HÜ RT - - - - o - - - - o - - + + +

22 Bora x WL RT + + + + + + + + + + + + + + +

23 Boric a cid 10 RT + + + + + + + + + + + + + + +

24 Hyd rob ro mic a cid 10 RT - - - - - - - - - - - o o - +

25 Hyd rob ro mic a cid 50 RT - - - - - - - - - - - - - - +

26 But a no l UV RT + + + + + + + + + + + + + + +

27 But yl a ce ta t e UV RT + + + + + + + + + + + + + + +

/ / / - + + + + - - + + - +

/ / / - + + + + / / + + / +

/ / / - + + + + - - + + - -

/ / / + + + + + / / + + - /

/ / / / + + + + - + + + o /

/ / / + + + + + + + + + + +

/ / / + + + + + + / + + / +

/ / / + + + + + + - o o - /

/ / / + + + + + + / o o - -

/ / / - + + + + / - + + + -

/ / / + + + + + + + + + - -

/ / / + + + + o - - + + - /

/ / / + + + + / / / + + - /

/ / / + + + + + + / + + / /

/ / / o + + + + - - + + - -

+ + + + + + + o + o + + o -

+ + + + o o o o - o + + o -

/ / / + o o o o - - + + - -

/ / / + + + + + + - + + / /

/ / / + + + + + / - + + o -

/ / / + + + + + + - + + - +

/ / / + + + + / / + + + / /

/ / / + + + + + + + + + + +

/ / / + + + + + + / + + + /

/ / / + + + + + + / o o / /

/ / / + + + + + + + + + o +

/ / / + + + + / / - + + - o

C o n c e n t r a t i o n %

T e m p e r a t u r e ° C

P o l y a m i d e 6 C a s t

P A 6 G

P o l y a m i d e 6 C a s t , h e a t s t a b i l i s e d

P A 6 G

- W S

P o l y a m i d e 6 C a s t / M O S

P A 6 G

+ M o S 2

C a l a u m i d ®

6 1 2

P A 6 / 1 2 G

C a l a u m i d ®

1 2 0 0

P A 1 2

G

O i l a m i d ®

P A 6 G

+ Ö l

P o l y a m i d e 6

P A 6

P o l y a m i d e 6 / G l a s s f i b r e

P A 6 +

G F 3 0

P o l y a m i d e 6 6

P A 6 6


P A 1 2

P o l y a c e t a l C o p o l y m e r

P O M -

C

P o l y a c e t a l C o p o l y m e r / G l a s s f i b r e

P O M -

C - G F 3 0

P o l y e t h y l e n e t e r e p h t a l a t

P E T

P o l y e t h y l e n e t e r e p h t a l a t e / l u b r i c a n t a d d . P E T - G

L

P o l y t e t r a f l u o r o e t h y l e n

P T F E

P o l y t e t r a f l u o r o e t h y l e n / G l a s s f i b r e

P T F E +

G F 2 5 % G

l a s s f i b r e

P o l y t e t r a f l u o r o e t h y l e n / C a r b o n

P T F E +

2 5 % C

a r b o n

P o l y t e t r a f l u o r o e t h y l e n / B r a s s

P T F E +

4 0 % B

r a s s

P o l y v i n y l d i f l u o r i d

P V D F

P o l y e t h y l e n e 3 0 0

P E - H D


P E - H M W

P o l y e t h y l e n e 1 0 0 0

P E - U H M W

P o l y p r o p y l e n e

P P - H

P o l y v i n y l c h l o r i d e

P V C - U

P o l y c a r b o n a t e

P C

P o l y e t h e r k e t o n e

P E E K

P o l y e t h e r k e t o n e m o d i f i e d

P E E K - G L

P o l y s u l f o n e

P S U

P o l y e t h e r a m i d e

P E I

UV = u nd ilu te d

WL = a q u e o u s so lu t io n

G L = sa t u ra t e d so lu t io n

HÜ = co m m e rcia l q u a l it y

RT = r o om t em pe ra t ure

+ = resist a nt

o = lim it ed re sist a nt

- = no t resist a nt

L = so lub le

/ = n ot te st ed

As of 9/2004



Chemical resistance

29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

+ o + + + + + + + + + / / /

+ o + + / / + + + + + / / /

/ / + + + + + + + + + / / /

- L + + L - o o o o + / / /

/ / + + / / + + + + + / / /

- L + + L - o o o o + / / /

+ o + + + + + + + + + / / /

/ o + + / + o o o o + / / /

/ o + + o + + + + + + / / /

- o + + o + + + + + + / / /

/ L + + - + + + + + o / / /

o + + + - / / o o o o / / /

- L + + - - o o o o + / / /

/ / + + / - o - - - + / / /

+ - + + + + + + + + + / / /

+ - + + + + + + + + + / / /

/ / + + / + + + + + o / / /

+ + + + + + + + + + + / / /

+ + + + + + + + + + + / / /

+ + + + o + + + + + + / / /

- - + + - o + + + + + / / /

- - + + - - o o o o o / / /

+ o + + - - o o o o + / / /

o - L L - + + + + + + / / /

- - + + + + + + + + + / / /

+ o + + - + + + + + + / / /

+ + + + - + + + + + / / / /


P E I


P S U

P o l y e t h e r k e t o n e / m o d i f i e d

P E E K -

G L

P o l y e t h e r k e t o n e

P E E K


P C


P V C - U


P P - H

P o l y e t h y l e n e 1 0 0 0

P E - U H M W


P E - H M W


P E - H D

P o l y v i n y l d i f l u o r i d e

P V D F

P o l y t e t r a f l u o r o e t h y l e n e / B r a s s

P T F E +

4 0 % B

r a s s

P o l y t e t r a f l u o r o e t h y l e n e / C a r b o n

P T F E +

2 5 % C

a r b o n

P o l y t e t r a f l u o r o e t h y l e n e / G l a s s f i b r e

P T F E +

G F 2 5 % G

l a s s f i b r e

P o l y t e t r a f l u o r o e t h y l e n e

P T F E


L

P o l y e t h y l e n e t e r e p h t a l a t

P E T


P O M -

C - G F 3 0

P o l y a c e t a l - C o p o l y m e r

P O M -

C


P A 1 2


P A 6 6


P A 6 +

G F 3 0

P o l y a m i d 6

P A 6

O i l a m i d ®

P A 6 G

+ Ö l

C a l a u m i d ®

1 2 0 0

P A 1 2 G

C a l a u m i d ®

6 1 2

P A 6 / 1 2 G


P A 6 G

+ M o S 2


P A 6 G

- W S


P A 6 G



L = so lub le

/ = n ot te st ed


+ = resist a n t



UV = u nd ilu te d



HÜ = co m me rcia l q u a lit y

As of 9/2004

+ + + o o + + + + + + + + + + RT 5 Ca lcium chlo ride 28

+ + + - - - L L L - - - - - - RT 20 ‘’ ‘’ in a lcoho l 29

+ o o - - - - - - - - - - - - RT GL Ca lcium hypo chlo ride 30

+ + + o + + + + + + + + + + + RT UV Chlorb enzene 31

+ - - - - - - - - - - - - - - RT UV Chlo roa cet ic a cid 32

+ - - - - o o o o o o o o o o RT UV Chloro f o rm 33

+ + + o o o o o o o o o o o o RT 1 Chromic a cid 34

+ + + - - - - - - - - - - - - RT 50 Chromic a cid 35

+ + + + + + + + + + + + + + + RT UV Cyclo hexa ne 36

+ + + + + + + + + + + + + + + RT UV Cyclo hexa no l 37

+ - - + + + + + + + + + + + + RT UV Cyclo hexa no ne 38

+ + + + + + + + + + + + + + + RT UV Dib ut yl pht a la te 39

+ - - + + + + + + + + + + + + RT UV Dichlo re t ha ne 40

+ L L L L + + + + + + + + + + RT UV Dichlo re thylene 41

+ / / o o - - - - - - - - - - RT GL Iron(II)ch lo rid 42

+ / / o o - - - - - - - - - - RT GL Iron(III)ch lo rid 43

+ + + + + + - - - - + - - - - RT HÜ Vineg a r 44

+ + + + + + + + + + + + + + + RT 5 Acet ic a cid 45

+ + + o o + o o o o + o o o o RT 10 Acet ic a cid 46

+ + + - - o - - - - o - - - - 50 10 Acet ic a cid 47

+ - - - - - - - - - - - - - - RT 95 Acet ic a cid 48

+ - - - - - - - - - - - - - - 50 95 Acet ic a cid 49

+ + + + + + + + + + + + + + + RT UV Et hylet her 50

+ - - - - L L L L L L L L L L RT WL Hydro f luo ric a cid 51

+ + + + + o o o o o o o o o o RT UV Forma ldehyde 52

+ + + + + + + + + + + + + + + RT UV G lycerine 53

+ + + + + + + + + + + + + + + RT HÜ Fuel 54



Chemical resistance

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

55 Hept a no l UV RT + + + + + + + + + + + + + + +

56 Hexa ne UV RT + + + + + + + + + + + + + + +

57 Iso propa no l UV RT + + + + + + + + + + + + o o +

58 Po ta sh lye 10 RT + + + + + + + + + + + + - - +

59 Po ta sh lye 10 80 + + + + + + + + + + + + - - +

60 Po ta sh lye 50 RT o o o o + o o o o + + + - - +

61 Keto ne (a lipha t ic) UV RT o o o o o o o o o o + + - - +

62 Met ha no l 50 RT + + + + + + + + + + + o o + +

63 Met ha no l UV RT + + + + + + + + + + + o o + +

64 Met hylene chlo rid UV RT - - - - o - - - - o - - - - +

65 Minera l o il HÜ RT + + + + + + + + + + + + + + +

66 So d ium hypochlo rid e 10 RT - - - - - - - - - - - - o o +

67 So d ium lye 10 RT + + + + + + + + + + + + o o +

68 So d ium lye 10 80 - - - - - - - - - - + + - - +

69 So d ium lye 50 RT o o o o o o o o o o + + - - +

70 So d ium lye 50 80 - - - - - - - - - - + + - - +

71 Nit ro benzene UV RT - - - - - - - - - - o o o o +

72 Nit ro to luene UV RT o o o o o o o o o o o o + + +

73 Oxa lic a cid 10 RT o o o o o o o o o o - - + + +

74 Pheno l 90 RT L L L L L L L L L L - - - - +

75 Pheno l UV 40 L L L L L L L L L L - - - - +



78 Phosphoric a cid 10 RT - - - - - - - - - - + + + + +

79 Phosphoric a cid 25 RT - - - - - - - - - - o o + + +

80 Phosphoric a cid 85 RT L L L L L L L L L L - - + + +

81 Propa no l UV RT + + + + + + + + + + + + + + +

/ / / + + + + o + + + + o +

/ / / + + + + + + - + + o +

/ / / + + + + + + - + + o /

/ / / + + + + + + - + + o +

/ / / o - - - + - - + + o -

/ / / + + + + + + - + + o -

/ / / / + + + / / / + + / /

/ / / + + + + + + - + + o +

/ / / + + + + + + - + + o +

/ / / + o o o o L - + + L L

+ + + + + + + + + + + + + +

/ / / + + + + o + + + + + /

/ / / o + + + + + o + + + o

/ / / o o o o + o - + + + -

/ / / o + + + + + - + + + -

/ / / o o o o + o - + + + -

/ / / + + + + + - L + + - -

/ / / / + + + + - - + + / /

/ / / + + + + + + + + + + +

/ / / + + + + + o L + + - -

/ / / + + + + + - L + + - -

/ / / o - - - - - L + + - -

/ / / o - - - - - L + + - -

/ / / + + + + + + + + + + +

/ / / + + + + + + + + + + +

/ / / + + + + + + + + + o -

/ / / + + + + + + + + + + +

C o n z e n t r a t i o n %



P A 6 G


P A 6 G

- W S


P A 6 G

+ M o S 2

C a l a u m i d ®

6 1 2

P A 6 / 1 2 G

C a l a u m i d ®

1 2 0 0

P A 1 2 G

O i l a m i d ®

P A 6 G

+ Ö l

P o l y a m i d e 6

P A 6


P A 6 - G F 3 0


P A 6 6


P A 1 2

P o l y a c e t a l C o p o l y m e r

P O M -

C


P O M -

C - G F 3 0

P o l y e t h y l e n t e r e p h t a l a t e

P E T


L


P T F E


P T F E +

G F 2 5 % G

l a s s f i b r e


P T F E +

2 5 % C

a r b o n


P T F E +

4 0 % B

r a s s

P o l y v i n y l i d i f l u o r i d e

P V D F


P E - H D


P E - H M

W

P o l y e t h y l e n e 1 0 0 0

P E - U H

M W


P P - H


P V C - U


P C

P o l y e e t h e r k e t o n e

P E E K

P o l y e t h e r k e t o n e / m o d i f i e d

P E E K -

G L


P S U


P E I

UV = u nd ilut ed



H Ü = co m m e rcia l q u a l it y


+ = resist a nt



L = so lub le

/ = n ot te st ed

As of 9/2004



Chemical resistance

29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

+ + + - - - - - - - - - - - - RT 10 Nit ric a cid 82

+ - - - - - - - - - - - - - - RT 80 Nit ric a cid 83

+ - - - - L L L L L L L L L L RT 50 Nit ric a cid 84

+ - - - - L L L L L L L L L L RT 80 Nit ric a cid 85

+ o o - - - - - - - - - - - - RT 10 Hydrochlo ric a cid 86

+ o o - - - - - - - - - - - - RT 20 Hydrochlo ric a cid 87

+ - - - - L L L L L L L L L L RT 30 Hydrochlo ric a cid 88

+ o o - - - - - - - - - - - - RT 40 Sulphuric a cid 89

+ o o - - - - - - - - - - - - 60 40 Sulphuric a cid 90

+ - - - - L L L L L L L L L L RT 96 Sulphuric a cid 91

+ - - - - L L L L L L L L L L 60 96 Sulphuric a cid 92

+ + + o o + + + + + + + + + + RT UV Ca rbo n te t ra chlo ride 93

+ + + + + + + + + + + + + + + RT UV Tolua l 94

+ o o o o o o o o o o o o o o RT UV Trichlo re thylene 95

+ + + + + + + + + + + + + + + RT 10 Hyd rog en peroxide 96

+ + + + + o - - - - o - - - - RT 20 Hyd rog en peroxide 97

+ + + o o - - - - - - - - - - RT 30 Hyd rog en peroxide 98

+ + + - - - - - - - - - - - - 60 30 Hyd rog en peroxide 99

+ + + + + + + + + + + + + + + RT UV Xylene 100

+ + + + + + o o o o + o o o o RT 10 Cit ric a cid 101

+ + + - - o o o o o o o o o o 5 0 10 Cit ric a cid 102

+ + + + - + + + + + + / / /

/ / + + - - - - - - + / / /

/ + o o - - - - - - + / / /

/ + o o - - - - - - o / / /

+ + + + + + + + + + + / / /

+ + + + + + + + + + + / / /

+ o + + o + + + + + + / / /

+ + o o + + + + + + + / / /

o o - - o o + + + + + / / /

- L L L - + o o o o + / / /

- L L L - o - - - - + / / /

+ + + + - - - - - - + / / /

- - + + - - o o o o + / / /

- L + + - - o o o o + / / /

+ + + + + + + + + + + / / /

+ + + + + + + + + + + / / /

+ + + + + + + + + + + / / /

/ / + + / o o o o o / / / /

o o + + - - o o o o + / / /

+ o + + + + + + + + + / / /

+ o + + / + + + + + + / / /


P E I


P S U

P o l y e e t h e r k e t o n e m o d i f i e d

P E E K -

G L

P o l y r e t h e r k e t o n e

P E E K


P C


P V C - U


P P - H

P o l y e t h y l e n e 1 0 0 0

P E - U H

M W


P E - H M

W


P E - H D

P o l y v i n y l i d i f l u o r i d

P V D F


P T F E +

4 0 % B

r a s s


P T F E +

2 5 % C

a r b o n


P T F E +

G F 2 5 % G

l a s s f i b r e


P T F E


L

P o l y e t h y l e n e t e r e p h t a l a t e

P E T

P o l y a c e t a l - C o p o l y m e r / G l a s s f i b r e

P O M -

C - G F 3 0

P o l y a c e t a l - C o p o l y m e r e

P O M -

C


P A 1 2


P A 6 6


P A 6 +

G F 3 0

P o l y a m i d e 6

P A 6

O i l a m i d ®

P A 6 G

+ Ö l

C a l a u m i d ®

1 2 0 0

P A 1 2 G

C a l a u m i d ®

6 1 2

P A 6 / 1 2 G


P A 6 G

+ M o S 2


P A 6 G

- W S


P A 6 G



L = so lub le

/ = n ot te st ed


+ = resist a n t



UV = u nd ilu te d



HÜ = co m me rcia l q u a lit y

As of 9/2004



Our machining capabilities:• CNC milling ma chines, w orkpiece capa city u p t o ma x. 2000 x 1000mm• 5-a xis CNC milling ma chines• CNC lat hes, chucking ca pa city up t o m a x. 1560 mm d iame te r an d 2000 mm long• Screw ma chine lat hes up to 100mm diame ter spindle sw ing• CNC auto ma tic lat hes up to 100mm diame ter spindle sw ing• Gear cutt ing machines for gea rs sta rt ing a t Module 0,5

• Profile milling (sha ping a nd molding)• Circular sa w s up to 170mm cutting thickness a nd 3100mm cutting lengt h• Fou r-side d pla ners up to 125mm th ickness a nd 225mm w idth• Thickness plane rs up t o 230mm t hickness an d 1000mm w idth



We process:• Po lya mide PA• Polyacetal POM• Polye thylene terephtha la te PET• Po lyet hylen e 1000 PE-UHMW• Po lyet hylen e 500 PE-HMW• Po lyet hylen e 300 PE-HD

• Polypropylene PP-H• Po lyvinyl chlorid e (ha rd) PVC-U• Polyvinylide ne fluoride PVDF• Polyte tra fluoro et hylene PTFE• Polyetheretherketone PEEK• Po lysulpho ne PSU• Po lyet her imid e PEI

Examples of parts:• Rope shea ves an d casto rs• Guide ro llers• Deflection shea ves• Friction be a ring s• Slider pad s• Guide ra ils

• Gear w heels• Sprocket w heels• Spind le nut s• Curved fee d ta bles• Feed t ab les• Feed screw s

• Curved gu ides• Met ering disks• Curved d isks• Threa de d joints• Seals• Inspection g lasses

• Va lve seat s• Eq uipment casings• Bobbins• Va cuum ra ils/pa ne ls• Stripper rails• Punch supports



I n f o r m a t i o n o n h

o w t o

u s e t h i s d o c u m e n

t a t i o n / B i b l i o g r a p h y

Information on how to use this documentation

All calculations, design s a nd t echnical det a ils are o nly intend ed a s informa tion a nd a dvice an d dono t replace te sts by th e users in reg a rd to th e suita bility of th e ma te ria ls fo r specific a pplicat ions.No leg al ly binding a ssuran ce of prop erties and /or results f rom t he calcula t ions can be ded uced

from t his do cument. The ma terial param ete rs sta ted here are no t binding m inimum values, rat herthey should be rega rded a s guiding va lues. If no t o therw ise sta ted , they were de t ermined w ithstan da rdised samples at room tem perat ure a nd 50% rela tive humidity. The user is respon sible forthe d ecision as to w hich ma ter ia l is used f or w hich a ppl ica t ion a nd f or the pa r ts ma nufa cturedf rom t he ma ter ia l . Hence , w e recomm end t ha t pract ica l tes ts a re ca rr ied o ut to de t ermine thesuita bility bef ore prod ucing a ny pa rts in series.

We expressly reserve the righ t t o m a ke chang es to this document . Errors excepte d.You can d ow nload the la t es t version cont a in ing a ll cha ng es and supplement s as a pdf f i le a twww.l icharz .de.

© Copyright b y Licha rz GmbH, German y

Bibliography

The fo llow ing litera ture w as used t o compile “ Desig ning w ith plastics” :

Eb eling , F.W. /Lüpke, G . Kunst st of f vera rb eit ung ; Vo gel Verla gSche lte r, W. /Schw a rz, O.

Biederb ick, K. Kunststo ff e; Vog el Verlag

Ca rlo w it z , B. Kunst sto f f t a b ellen ; Ha nser Verla g

Bög e, A. Da s Techniker Hand bu ch; View eg Verlag

Ehrenste in, Go tt fried W. Mit Kunststo ff en Konstruieren; Hanser Verlag

Strickle, E. /Erha rd G. Ma schinen elemen te a us th ermo plastischen Kunststo ff enGrundlag en und Verbindung selement e; VDI Verla g

Strickle, E. /Erha rd G. Ma schinen elemen te a us th ermo plastischen Kunststo ff enLa g er un d Ant riebselement e; VDI Verlag

Erha rd, G. Kon struieren mit Kunststo ff en; Han ser Verlag

Severin, D. Die Besond erheiten von Räd ern aus PolymerMaterialen;Specialist repo rt, B erlin Techn ica l Universit y

Severin, D. /Liu, X. Zum Ra d-Schiene -Syst em in de r Förd ert echn ik,

Specialist repo rt, B erlin Techn ica l Universit y

Severin, D. Tea ching ma te rial Nr. 701, Pressung en

Liu, X. Persona l info rma tion

Becker, R. Persona l info rma tion

VDI 2545 Za hnrä de r a us th ermo plastischen Kunststo ff en; VDI Verlag

DIN 15061 Pa rt 1 Gro o ve pro f iles f o r w ire ro pe shea ves; Beut h Verla g

DIN ISO 286 ISO coding syste m fo r to leran ces a nd fits; Beut h Verlag

DIN ISO 2768 Pa rt 1 Genera l t o lera nces; Beut h Verla g

DIN ISO 2768 Pa rt 2 Genera l t o lera nces f o r fea tures; Beut h Verla g



For further information, detailed catalogs are available:

• Info rmat ion on Licha rz machining capa bilities of compo nent pa rts• Brochure „ Ma te ria l Guiding Va lues /chemica l Resistan ce“

• Product information on semi-finished products of PA, POM und PET

• Delivery progra mme

Visit us on th e internet at www.licharz.de

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designing with engineering plastics

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