Production ofSelf lubricatingSintered BearingsAutolube®

Sintec was founded in 1987 andoperates in the powder metallurgysector.Our innovative technology, the highquality of our products, theproductive and commercialflexibility, are the basis to gain abigger domestic and internationalmarket share.In the last few years, we haveconsolidated our market position,becoming one of the leaders in theproduction of Self lubricatingSintered bearings.We are in open competition withthe other big European Companiesoperating in powder metallurgy.

Markets assistedItaly, UE and extra UEIndustrial SectorAutomotive, Household appliances,Hobbies,Electrical MotorsProduction capability100 millions of sintered bearingsper year

The Company

The constant technologicaldevelopment and themanufacturing control system arethe basis to assure high qualityproducts, required by automotiveand electrical markets.Sintec has developed an ownquality management systemcompliance with the standard UNIEN ISO 9001.

Our Quality

20 Forming Presses (4-40 Ton)6 Sizing Presses (35 Ton)3 Sintering Furnaces4 Impregnation lines2 Equipment for oil free surfaces2 Burr removing machines

Sintec in equipped to meet allcustomer requirements throughstatistical control of all productionprocess and steps.- For internal, external diameter,concentricity and length- For density and quantity oflubricant- For the determination of powderdimensions and his distribution- Flowmeter- For radial strength- Shape Roundness MMQ10- Roughness

Plants and Equipments

Measurement Equipments

Autolube® Product

2

AUTOLUBE® bearing is a mechanicalprecision element that allows torealize tribological systemscharacterized by a good economicconvenience. It is the best solution forall the appliances in which apermanent lubrication is needed, inrotation or translation systems (smalland medium electrical motors, slides,tools, household appliances, etc.)It is realized in standard (Cylindrical,spherical, flanged ) or special formsfollowing Clients needs.

Limitations:limited economicity for small

quantitieslimited specific loads

Advantages:good economic convenienceself lubricating attitudeno maintenanceimproved noise characteristicsadaptation to the specific applicationform repeatability withhigh precisionsimple assembly

The characteristic function of selflubricating bearings AUTOLUBE® isbased on a symbiotic relation betweenthe porosity load carrying member(bearing) and the shaft in rotationmovement, supported by the lubricantabsorbed in the porosity of the bearingthat can be exactly controlled by theP/M manufacturing process.

With speed of rotation up than 0,25m/sec, hydrodynamic conditions arereached, it means that the shaft floatson the lubricant without metallicfriction.

This resulting tribosystem allowappliances function without otherfurther oil contribution.

The correct definition of thetribosystem requires a good projectingexperience. These technicalinformations have the goal to explainto our Customers the fundamentalconcepts of self lubricating bearing.For assistance, please contactSINTEC technical office.

The design of bearingsAutolube®

3

The design of self lubricating bearingmust guarantee stable hydrodynamiccondition that means a minimumfriction coefficient (µ min).

Between starting and stop period thesystem transits in a mixed frictionregime that required an optimumfriction coefficient between theelements involved in the system.(shaft and bearing).

The efficiency of the system can bemanaged using the Stribeck Curve orthe temperature-time diagram (T-t)

coef

ficie

nte

d’at

trito

f

numero di giri n

Att. misto Lubrificazione idrodinamicaAtt.

Rov

ente

coef

ficie

nte

d’at

trito

f

numero di giri n

Att. misto Lubrificazione idrodinamicaAtt.

Rov

ente

coef

ficie

nte

d’at

trito

f

numero di giri n

Att. misto Lubrificazione idrodinamicaAtt.

Rov

ente

0

25

50

75

100

125

0 1 2 3 4

4321

t (h)

T(°C)

0

25

50

75

100

125

0 1 2 3 4

4321

t (h)

T(°C)

Stribeck Curve

Temperature – Time Diagram

Curva 1

n: 2.800 giri/min

p: 0,75 N/mm2

Ø: 6 mm

Curva 2

n: 2.800 giri/min

p: 1,2 N/mm2

Ø: 6 mm

Curva 3

n: 2.800 giri/min

p: 2 N/mm2

Ø: 6 mm

Curva 4

n: 2.800 giri/min

p: 2,8 N/mm2

Ø: 6 mm

Curva 1

n: 2.800 giri/min

p: 0,75 N/mm2

Ø: 6 mm

Curva 2

n: 2.800 giri/min

p: 1,2 N/mm2

Ø: 6 mm

Curva 3

n: 2.800 giri/min

p: 2 N/mm2

Ø: 6 mm

Curva 4

n: 2.800 giri/min

p: 2,8 N/mm2

Ø: 6 mm

Conventional connection

4

Shaft – Bearing

p p

FF

ω

r

R

en1

Dd

R(D): bearing internal radiusr(d): shaft radiusF: load applied on the shaftp: hydrodynamic film pressureω: rotary speed and directione: system eccentricityn1: oil film thicknessn1+e: theoretical static clearance

Surface of grinded bearing

Tribosystem

5

Shaft – Sintered Bearing

Surface of sized sintered bearing

ω

Oil in theporosity

Loadsurface

Shaft

Bearing

p p

FF

ω

r

R

en1

Dd

R(D): bearing internal radiusr(d): shaft radiusF: load applied on the shaftp: hydrodynamic film pressureω: rotary speed and directione: system eccentricityn1: oil film thicknessn1+e: theoretical static clearance

ConnectionShaft – Sintered bearing

6

HYDRODYNAMIC condition: F=Σp

The shaft is supported by a oil filmwithout metallic contact.The hydrodynamic film is generated bythree effect:

specific pressure p due to Ftemperature increase (thermic

expansion)driving on the shaft surface

a) Stationary (ω=0)

p

R

r

b) Running (ω≠0)

P

R

n1 Fω

r

e

ω

p

F

R(D): bearing internal radiusr(d): shaft radiusF: load applied on the shaftp: hydrodynamic film pressureω: rotary speed and directione: system eccentricityn1: oil film thicknessn1+e: theoretical static clearance

The production process

FORMING AREA SINTERING SIZING AREA

IMPREGNATION QUALITY OFFICE7

Basepowder

LubricantMetal alloypowder

Mixing

Load Pressing Ejection

Sintering

800 – 1250°C

Deburring Sizing Impregnation Centrifuging

Packaging

Material Table for bearingAutolube®

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Lubricant Table for bearingsAutolube®

9

Diagramdensity – open porosity

10

Working area Oiled Density in g/cm3

Ope

n Po

rosi

ty in

%

HighDensityMaterial

LowViscosityLubricant

LowDensityMaterial

HighViscosityLubricant

Density for bearing Autolube®

BRONZE P-50.B-68 density 6,8 g/cm3

BRONZE + GRAPHITE P-51.B-66 density 6,6 g/cm3

IRON P-00.F-62 density 6,2 g/cm3

IRON COPPER P-10.F-62 density 6,2 g/cm3

Standard shapes for

Autolube® Bearings

11

Spherical Bearing

Guarantee the autoalignment of the hole.During the assemblydoes not sufferdimensional changes.

Dc

d

h Ds

Spherical Bearing

Guarantee the autoalignment of the hole.During the assemblydoes not sufferdimensional changes.

Dc

d

h Ds

Flanged Bearing

Same assemblingprocedures of cylindricalbearing. The Flange atone end serves as a stopgauge in assembly.

Df

d

h

D

Flanged Bearing

Same assemblingprocedures of cylindricalbearing. The Flange atone end serves as a stopgauge in assembly.

Df

d

h

D

Spherical Bearingwith Boss

The same of SphericalBearing plus the bossused as distance piecein intermediate spacing

d

Dc

hDs

hc

Spherical Bearingwith Boss

The same of SphericalBearing plus the bossused as distance piecein intermediate spacing

d

Dc

hDs

hc

Cylindrical Bearing

It is the simplestbearing, usually usedas distance piece.Assembled with thehelp of a fitting pin.

D

d

h

Recommended Tolerances forbearings Autolube®

12

Design of a self LubricatingSintered Bearing Autolube®

13

Design of a BearingData of a tribo-systems:d: shaft diameter ………5mmn: rotational speed……2.800 rpmF: max load applied ..…100 NStandard conditions:- Horizontal assembly- Temperature range -20°C ÷ +100°C

Formulas used:•F = p x A , A = F/p = 100/2,8 = 35,7mm2

where:p: specific pressure obtained fromload diagram (2,8N/mm2)A: support area

• A = d x b b = A/d = 35,7/5 =

= 7,17 mm

where:

b: bearing length

• b1=b+2 x chamfer = b + 2 x 0,3 =7,77 mm

From these calculations result alength of 8mm

Test of a BearingKnown geometrical characteristics of abearing, we want to calculate the maximumload applicable.Data:d: shaft diameter ………5mmn: rotational speed……1.400 rpmb1: Total length …….7mmChamfer 0,3 x 45°

Formulas used:•F = p x A

where:p: specific pressure obtained fromload diagram (5,5 N/mm2)A: support area

• A = d x (b1 – 2 x chamfer) =

5 x (7-2x0,3) = 32 mm2

Results

• F = p x A = 5,5 x 32 = 176 N

The bearing can support a maximumload of 176 N

Load Diagrams

14

0

1

2

3

4

5

6

7

8

250 500 750 1000 1500 2000 2500 3000 4000 5000

ø 2 ø 4 ø 6 ø 8 ø 12 ø 16 ø 20

0

1

2

3

4

5

6

4.000 5.000 10.000 15.000 20.000

ø 2 ø 4 ø 6 ø 8

N/m

m2

Rev/min

N/m

m2

Rev/min

Considerations aboutBearing clearance

15

In order to guarantee hydrodynamiclubrication, it is important to maintaina minimum clearance of the tribo-system.

The minimum diameter clearance,should not be lower then 1‰ of theshaft diameter value, to guaranteegrowth and stability of oil film.

The maximum clearance applicabledepends on working clearances thatnormally are IT4 for the shaft and IT6for bearings.

.

Excessive clearances can be cause ofnoise. Excessive noise can be avoidusing oils with higher density.

In assembling of Cylindrical andflanged bearings it is very important toverify bore clearance after the bearingis in place.

Shaft Diameter in mm

Dia

met

ral

Cle

aran

ce in

µ DIAGRAM OF MINIMUM DIAMETRALCLEARANCE

Assembly Guidelines

16

Flanged and Cylindrical bearings areassembled with the method of pressfitting. During press fitting theinterference between Housing andbearing, cause a restriction of theinternal diameter. This restrictiondepends by many factors, as theresistance of the materials and theirthickness.

This diagram gives an indication ofthe percentile of restriction in functionof the external diameter of thebearing and the thickness wall.

0

10

20

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35

1 mm1.5 mm3 mm

5 mm

External diameter (mm)

Res

tric

tion

of th

e in

tern

al d

iam

eter

in %

of

the

clea

ranc

e

The restriction is referred to the internaldiameter without a fitting pin. In order tomaintain the required assembledtolerance, the bearing should beassembled with the help of a fitting pin.

Thickness

Assembly guidelines

17

Example of assembling a cylindricalbearing.

Internal Diameter 5 (G7) (+4, +16)External Diameter 9 (r6) (+19, +28)Housing 9 (H7) (+15)Thickness 2 mm

From the diagram results a restriction %of 82% of the clearance.

So without a fitting pin the internaldiameter is: 4,981 ÷ 5,013

The required diameter is 5 (H7), so5,000 ÷ 5,012

To guarantee this condition the usageof a fitting pin is necessary, and itsmeasure should be 5,008

N.B: we suggest the usage offitting pin in hard metal withworking tolerance IT3. Maintainfitting pins clean and lubricated.

Ra

≤ 0,

5

0,001 Ø 5,008m3

R

Cylindrical and flanged bearings

Assembly guidelines

18

Spherical bearings, with or without boss, don’t suffer of diameter restriction,because they are not inserted in press fit. Consequently, the tolerances of thedelivered bearings correspond with those of the assembled

Spherical bearings

Internal diameter of bearing (mm)

Min

imum

def

lect

ing

torq

ue in

N/1

00m

m

Attention: too high deflecting torque does not permit the correct alignment ofthe bearings in the housing to the shaft. As guide line for the calculation ofthe maximum deflecting torque it is possible to double diagram values.

100 mm

F (N)

d

M = F x 100 mm (Nmm)

F = M/100 (N)

Shafts

One of most important components ofthe tribo-system is the shaft, that runsor slides inside the sintered component.Generally they are in steel, and it canbe hardened or unhardened dependingupon the application.

Most common used materials are:

• Quality steel 60 Kg/mm2

Nr. 1.0060

• Carbon steel C60Nr. 1.0503

• Case hardened steel 16MnCr5Nr. 1.7131

• Tool steel UNI 100Cr6Nr. 1.2067

For shaft in rustless materials wesuggest to use Iron sintered bearings.

ROUGHNESS: very low values ofroughness are not requested. Tomaintain the oil movement and lowprice the suggested values are:between Ra 0,1 and 0,25 (DIN ISO1302).

SHAPE ERRORS: shape errors shouldbe limited to the order of < IT2. Thetolerance on the diameter can be IT3 orIT4.

ANTIRUST PROTECTION: Shaft mustbe clean to avoid bearing lubricantpollution. The safe coating protectionshould be compatible with the oil insidethe bearing.

Thrust Washers

Thrust washers stop axial movement ofthe shaft-bearing connection. Theyworks on the front surface of sinteredbearing.

• in order to guarantee an optimalfunction, thrust washers must have aplane surface and their roughness mustbe minimized;

• the external diameter must be higherthen the surface diameter of thesintered bearing;

• the edges must be burr-free in order toprevent centrifuging of oil.;

• Material used are: steel, hard tissueand plastic;

• in some cases two thrust washers areassembled together in order to create arelative motion;

• In order to avoid noise, it can beassembled with elastic materials ( e.g.springs, wavy washers, rubber orsynthetic washers.

Other components ofthe tribo-system

19

General advices

20

Deoling and Reimpregnation

We don’t suggest to make similaroperations, anyway, please contact ourtechnical service before to make thesecritical procedures.

Storage

We advise against too long opening oforiginal boxes before the usage.Sintered bearings are very sensitiveand any operation that can produce oilloss has to be avoided.

Do not use boxes with absorbentmaterials and protect bearings fromdust.

Take a special care in handling sinteredbearings, the surface of the bore canbe easily damaged.

Further Machining

The running surface of sinteredbearings should not be machined. Thisoperation destroy the surface, closingthe porosity of the bearings.

Bearing Housing

The housing of cylindrical and flangedbearings must be precise in shapeand dimension. The bearing duringthe fitting process can assume thehousing shape. Excessive low valuesof housing roughness are notnecessary.

Housing for spherical bearingsdoesn’t need machining after diecasting.

In designing the housing for sphericalbearing, it is advantageous to providespaces for grease or oil-saturatedfelts for additional lubrication

Sintered Bearings Life

21

The life of a self lubricating sinteredbearing depends upon the type ofassembly and working conditions.

One of the most important suggests isto avoid the oil loss.

The life of bearing systems withoutspecial protection, as long as there isno loss of oil, is up to 1.500 hours.

For bearing systems with additionallubrication but without oilrecirculation, the life is up to 4.000hours.

For bearing systems with additionallubrication and oil recirculation, thelife is over 4.000 hours.

The choice of oil is very important, inthis choice are to be considered theoperating conditions such asrotational speed, temperatures, loadsclearance.

In many case is very important toprotects the bearing system fromexternal factors such as dust, wateretc.

Durata di vita < 1.500 h

Durata di vita > 4.000 h

Durata di vita fino a 4.000 h

Additional lubrication

Clearance Values

22

Internal Diameter

Clearance Values

21

External Diameter

23

Sintec s.r.l.Via Lainate, 145621042 Caronno Pertusella VAITALYTel. +39 02 99025065Fax +39 02 99026130E-mail: sintec@sintecsrl.comWeb Site: http://www.sintecsrl.com