role of drawing & combing

BZU TEXTILE ENGINEERS


D raw ing

Pure ly from comm erc ia l po in t o f v iew it is

o f ve ry little sign ific an ce and it u su a lly

con tr ibu tes le ss th an 5% to p rodu c tion co sts o f

th e ya rn . H ow eve r its in flu ence on q ua lity ,

e sp ec ia lly evenness , is a ll th e g rea te r fo r th is .

F u rthe r if th e d raw fram e is no t p rop e rly

ad jus ted , the re w ill a lso b e e ffec ts o n ya rn

s treng th and e lo nga tio n .


There are 2 main reasons for the considerable

influence of the drawframe on evenness.

1-Within the sequence of m/c in cotton spinning mill,

the drawframe is the definitive compensation point for

elimination errors. Inadequacies in the product leaving

the drawframe not only pass into the yarn, they are

actually reinforced by drafting effects following the

draw frame. The yarn is never better than the draw

frame sliver.


2-A defect arising at the draw frame can

exert an effect of significant proportions

on the overall process. High performance

draw frame currently produce over 200

KG of sliver per hour at each delivery.

Very large quantities of poor quality

sliver will be produced in the time that

elapses before discovery of the defect.


At drawing stage, material passes not only one m/c

but usually 2, arranged 1 after the other & combined

to form a group. Processing in 2 passages is

necessary completely to fulfill the requirements. The

2nd passage is often superfluous after combing m/c

because then it does not normally generate any

improvement in quality.

In old machinery 3 drawings were used, breaker,

intermediate & finisher. But now in latest m/c only 2

drawings, breaker & finisher are used & in D-35 only

one drawing is used.

Explanation:


Tasks of the draw frame:

• drafting

• equalizing

• parallelizing

• blending

• dust removal


Drafting:

The reduction of weight / yard of sliver

and increase in length is called drafting.

Or Attenuation of sliver without breaking

is called draft.

Break draft:

Draft b/w the 2nd and 3rd rollers is called

break draft.

Main draft:

Draft b/w the 2nd and front rollers is called

main draft.


Total draft:

Total draft = break draft * main draft


Types of draft:

1. actual draft:

It is the ratio b/w material feed and

material delivered.

Length/count delivered

Actual draft =

Length/count fed

Or

Weight fed / yard

Resultant Draft =

Weight delivered / yard


1. Mechanical draft:

It is the ratio b/w the surface

speed of delivery roller and surface speed of feed

roller.

Surface speed of delivery roller

Mechanical draft = Surface speed of feed roller


Drawing rolls:

Mainly a set of 3/3, 3/4, 4/3, 5/4 drafting

rollers is used in drafting action. And the top and

bottom rollers of each set are made of different

materials.

� Bottom roller is made of steel.

Top roller is also made of steel but covered with

leather for better grip of fiber strand.


Draft gear:

Draft constant

Draft gear =

Draft

Draft constant is calculated by putting the value of

changeable gear equal to 1, in draft equation.


E q u a l iz in g :

� O n e o f t h e m a in ta s k s o f d r a w f r a m e i s im p r o v in g

e v e n n e s s o v e r s h o r t , m e d iu m a n d e s p e c ia l l y , lo n g

te rm s .

� C a rd s l iv e r f e d h a s h ig h d e g r e e o f u n e v e n n e s s , a n d

th e s l i v e r f r o m c o m b e r c o n ta in s in f a m o u s p ie c in g s ;

th e s e m u s t b e o b s c u r e d .

� I t i s m i s ta k e to a s s u m e th a t s l iv e r e v e n n e s s ,

e s p e c ia l l y o v e r s h o r t l e n g th s , c a n b e s i g n i f ic a n t l y

im p r o v e d b y u s e o f s e v e r a l p a s s a g e s .

� A s e c o n d p a s s a g e b r in g s h a r d ly a n y im p ro v e m e n t

a n d a th i r d c a n a c tu a l l y l e a d to d e te r io r a t io n .

E q u a l iz in g i s a lw a y s p e r fo rm e d b y a f i r s t p r o c e s s ,

n a m e ly d o u b l i n g , a n d c a n o p t io n a l l y a l s o b e

p e r fo rm e d b y a s e c o n d p r o c e s s , n a m e ly a u to le v e l i n g .


P a r a l le l iz in g :

� T o o b ta in a n o p t im a l v a lu e fo r s tr e n g th in th e y a rn

c h a ra c te r is t ic s , th e f ib e r s m u s t b e a r r a n g e d p a ra l le l

in th e f ib e r s t r a n d .

� I t fu l f i l s th is ta s k b y w a y o f th e d r a f t , s in c e e v e r y

d ra f t in g s te p le a d s to s t r a ig h te n in g o f f ib e r s .

� T h e v a lu e o f d r a f t m u s t b e a d a p te d to th e m a te r ia l ,

i .e . to s e v e r a l f ib e r s p a r am e te r s ( h e r e , m a in ly th e

s ta p le le n g th ) a n d a ls o to :

� T h e m a s s o f f ib e r s :

� T h e v o lu m e o f th e s tr a n d :

� T h e d e g re e o f o rd e r (p a r a l le l

d is p o s i t io n ) .

I t w il l b e c le a r th a t th e d r a f t c a n n o t b e h ig h

im m e d ia te ly fo l lo w in g th e c a rd ( i f p o s s ib le n o t a b o v e

8 ) , b u t th e r e a f te r c a n in c r e a s e f ro m m /c to m /c .


B le n d in g :

� In a d d it io n to th e e q u a l iz in g e f f e c t , d o u b l in g a ls o

p ro v id e s a d e g re e o f c o m p e n s a tio n o f r a w m a te r ia l

v a r ia t io n , b y b le n d in g .

� T h is r e s u l t i s e x p lo ite d in p a r t ic u la r in th e

p ro d u c tio n o f b le n d e d y a r n s c o m p r is in g

c o t to n /s y n th e tic o r s y n th e t ic / s y n th e t ic b le n d s .

� A t th e d r a w f r am e th e m e te r in g o f in d iv id u a l

c o m p o n e n ts c a n b e c a r r ie d o u t v e r y s im p ly b y

s e le c t io n o f th e n um b e r o f s l iv e r s e n te r in g th e

m a c h in e .

� F o r e x am p le , to o b ta in a 6 7 :3 3 b le n d , fo u r s l iv e r s

o f o n e c o m p o n e n t a n d tw o o f o th e r a r e fe d to th e

d ra w f r am e . O f c o u r s e , th e s e s l iv e r s m u s t h a v e th e

s a m e h a n k .


Dust removal:

� Dust is becoming a great problem both in

processing and for the personnel involved.

� It is therefore important to remove dust to the

greatest practical extent at very possible point

within the overall process.

� Unfortunately, dust removal can only be carried

out to a significant degree when there are high

levels of fiber/fiber or fiber/metal friction, since a

large fraction the smallest particles (dust) adhere

relatively strongly to the fibers.

� Such friction arises especially at the card and the

draw frame: in the latter case, mainly owing to the

drafting operation.


Production:

Production of drawing frame depends

upon following factors:

1. speed of some parts

2. size of sliver delivered

3. hours per day

4. Stops.


Stop motions:

A stop motion is a device arranged to stop

the machine when certain undesired conditions exit.

Stop motions are applied at several places on

drawing machine. Although stopping the machine

causes a reduction in production, this disadvantage is

overbalanced by the improved quality of the product.

The three common drawing frame stop

motions are:

1. The spoon or back stop motion

2. The trumpet or calendar roll stop motion

The full can stop motion.


C om b in g

C o m b i n g i s a n i n t e r m i t t e n t

o p e r a t i o n i n w h i c h t h e s h o r t

f i b e r s , n e p s & d i r t a r e r e m o v e d

f r o m s l i v e r l a p b y f o l l o w i n g s t e p s .

1 . A n a r r o w l a p o f f i b e r i s

f i r m l y g r i p p e d a c r o s s i t s w i d t h

b y a p a i r o f s p e c i a l l y d e s i g n e d

j a w s .

2 . A s e r i e s o f f i n e c l o s e l y

s p a c e d n e e d l e s i s p a s s e d

t h r o u g h t h e f i b e r s p r o j e c t i n g

f r o m j a w s .

T h e t r e a t e d f i b e r s p r o j e c t i n g

f a r t h e s t f r o m t h e j a w s a r e d r a w n

a w a y t h r o u g h a n o t h e r s e r i e s o f f i n e

n e e d l e s .


Tasks of combing:

• To remove short fibers.

• To remove any neps & dirt

remaining with the

cotton.

To straighten the fibers and make

them parallel to each other.


V a l u e o f c o m b i n g :

T h e r e a r e s e v e r a l w a y s

i n w h i c h c o m b i n g m a y b e o f v a l u e

i n t h e m a n u f a c t u r e o f c o t t o n y a r n .

T h e v a r i o u s y a r n c h a r a c t e r i s t i c s

w h i c h m a y b e i m p r o v e d b y c o m b i n g

a r e l i s t e d a s f o l l o w s .

D u e t o m o r e u n i f o r m s t a p l e :

� C o m b i n g m a k e s p o s s i b l e s p i n n i n g a

m o r e u n i f o r m y a r n .


s t r o n g e r y a r n .


f i n e r y a r n .


D u e t o s t r a i g h t e n e d c o n d i t i o n s o f

f i b e r s :

� C o m b i n g m a k e s p o s s i b l e s p i n n i n g

s m o o t h e r a n d m o r e l u s t r o u s y a r n .

D u e t o r e m o v a l o f n e p s a n d d i r t :


c l e a n e r a n d f i n e r y a r n .

� I n a d d i t i o n y a r n m a d e o f c o m b e d

c o t t o n n e e d l e s s t w i s t t h a n c a r d e d

y a r n .

H o w e v e r t h e s e q u a l i t y i m p r o v e m e n t s

a r e o b t a i n e d a t t h e c o s t o f

a d d i t i o n a l e x p e n d i t u r e , o n m a c h i n e ,

f l o o r s p a c e & p e r s o n n e l t o g e t h e r

w i t h l o s s o f r a w m a t e r i a l .


Note:

1 . E l i m i n a t i o n o f s h o r t

f i b e r s p r o d u c e s a n

i m p r o v e m e n t i n s t a p l e l e n g t h

b u t i t a l s o e f f e c t t h e

f i n e n e s s o f r a w m a t e r i a l .

2 . I t a l s o i n c r e a s e s

p a r a l l e l i z a t i o n o f f i b e r s b u t

t h e h i g h d e g r e e o f

p a r a l l e l i z a t i o n m i g h t r e d u c e

i n t e r f i b e r a d h e s i o n i n t h e

s l i v e r t o s u c h a n e x t e n t t h a t

f i b e r s l i d e s a p a r t w h i l e

b e i n g p u l l e d o u t o f c a n .

D u e t o t h i s h i g h d e g r e e o f

p a r a l l e l i z a t i o n f i b e r s b r e a k o r

f a l s e d r a f t m a y p r o d u c e .


Degree of combing:

In some cases, combing is

classified by the amount of noil

removed.

� Where the percentage of noil is

not over 10%, it is often spoken

as semi combing.

� Where the noil percentage is b/w

10% to 20%, it is called as

regular combing.

Where the noil percentage is b/w

20% to 30%, it is called double

combing.


Comb waste:

The waste from comb is noil.

It consists of short fibers, neps &

dirt. The noil percentage is

calculated as:

Weight of noil

Noil percentage =

Weight of lap feed


Subdivision of combing:

For the purpose of detailed

study, combing may be considered a

series of independent operations,

each of which may be studied as an

isolated mechanical action, where

all are so timed and located that

the cotton passes through one after

the other process.


S t e p s o f c o m b i n g a c t i o n s :

C o m b i n g a c t i o n c a n b e e x p l a i n e d a s :

F e e d i n g :

T h i s i n t r o d u c e s t h e r i b b o n l a p s i n

a s e r i e s o f s h o r t l e n g t h s .

N i p p i n g :

T h i s g r i p s t h e f i b e r s b / w t w o j a w s

a s f o r h o l d i n g t h e f i b e r s w h i l e t h e

s h o r t f i b e r s , n e p s & d i r t a r e b e i n g

r e m o v e d .

C o m b i n g :

T h i s p a s s e s m a n y r o w s o f c l o s e l y

s p a c e d n e e d l e s t h r o u g h t h e f i b e r s

f o r p a r a l l e l i z a t i o n .


D e t a c h i n g :

T h i s c o n s i s t s o f :

M o v i n g t h e p r e v i o u s l y c o m b e d c o t t o n

b a c k w a r d s o t h e n e w l y c o m b e d f i b e r s

m a y o v e r l a p t h e o t h e r s .

D r a w i n g t h o s e f i b e r s w h i c h p r o j e c t

t h e f a r t h e s t f r o m t h e l a p i n t h e

n i p p e r s .

T o p c o m b i n g :

T h i s d r a w s t h e b a c k e n d o f t h e

d e t a c h e d f i b e r s t h r o u g h a r o w o f

c l o s e l y s p a c e d n e e d l e s , t h u s

s t r a i g h t e n i n g a n d c l e a n i n g t h e m a n d

p r e v e n t i n g s h o r t f i b e r s f r o m b e i n g

c a r r i e d a l o n g b y c o n t a c t w i t h t h e

l o n g f i b e r s .


Condensing:

This passes the web from the

detaching rolls through a trumpet

forming it in to a sliver.

Drawing:

This passes the slivers from all

the heads, as a narrow sheet,

through a series of drawing rolls

produce them to a normal weight.

Coiling:

This puts the sliver into a roving

can with a uniform arrangement.


Figure:


1. lap roller

2. lap roll

3. lap lattice

4. feed roller

5. bottom nipper

6. top nipper

7. comber

8. cylinder

9. brush

10. aspirator

11. detaching roller

12. short fibers(noil)

Major Parts Of Combing M/C.


R o v in g

R o v in g a s n e c e s sa ry e v il:

T h e d raw fram e p ro d u c e s a s liv e r th a t a lre a d y e x h ib it

a ll th e c h a ra c te r i s tic s re q u ire d fo r th e c re a tio n o f a

y a rn , n am e ly a n o rd e re d , c le a n s tra n d o f f ib e r ly in g

p a ra lle l to o n e a n o th e r .

I t is a fa ir q u e s tio n th a t to a sk w h y th is s l iv e r is n o t

u se a s fe e d m a te r ia ls fo r th e r in g s sp in n in g m a c h in e ,

in s te a d o f b e in g p ro c e sse d in a n e x p e n s iv e m a n n e r to

c re a te a ro v in g a s fe e d fo r sp in n in g .

The roving m/c itself is complicated, liable to faults,

causes defects, adds to production costs and deliver a

product that is sensitive in both winding and

unwinding.


Use of the machine is forced upon the spinner as a

necessary evil for two principal reasons.

� The first reason is related to the require draft sliver

is thick, untwisted strand that tends to drafting

arrangement of ring spinning machine in their

current forms , are not capable of

processing this strand in a single drafting operation

to create a yarn of short staple fibre that metals all

the demands. The fine, twisted roving is

significantly better suited to this purpose.

� The second reason is that drawframe cans represent

the worst conceivable mode of transport and

presentation of fed material to the ring spinning

machine.


In spite of this, considerable effort has been

extended over decades to eliminate the roving

frame. The effort is justified, but unfortunately

in relation to ring spinning it remains without

success. On the other hand, in all new spinning

process in the short staple spinning mill, the

roving frame has been made superfluous.


T a sk s o f r o v in g fram e:

1 . T he ch ie f ta sk o f ro v in g fram e is a tte nu a tio n o f

th e s liv e r .

2 . A s th e re su ltin g fin e s tra nd h a s sc a rce ly a n y

co he ren ce , p ro te c tiv e tw is t m u s t b e in se r te d in

o rd e r to h o ld it to g e th e r .

3 . T he th ird ta sk is n o t d ire c tly re la ted to

sp in n in g , b u t it is fo rm a tio n o f la rg e p ack age

th a t c an b e tra n sp o rted , s to red and d o nned o n

th e r in g sp inn in g m ac h in e .

I t is w ind in g o p e ra tio n ab o ve a ll th a t m ake s ro v ing

fram e a com p le x and tro ub le p lag ued m ach in e . T h is

w ind in g o p e ra tio n req u ire s , in a d d itio n to th e sp ind le

and fly e r , a c o n e d r iv e tran sm is s io n (o r v a r iab le

g ea r) , a d iffe ren tia l g ea r a nd a b u ild e r m o tio n .


Hank:

One hank equals 840 yards. And hanks per pound are

determined as follows:

7000 grains (1 pound)

Hanks per pound =

840 yards

1000 grains 8.33 grains

= =

120 yards 1 yard

================

Now 8.33 is a constant for calculating draft by

dividing 8.33 by weight of sliver.


Imparting tw ist:

T he flyer inserts the tw ist. Each flyer

ro tation creates one turn in the roving. In the final

analysis therefore, since the flyer ro tation rate is held

constant, tw ist per unit length of roving depends upon

the delivery rate and can be influenced accordingly,

since tw ist is given by:

F lyer ro tation rate (rpm)

T urns per meter =

Delivery speed (m /m in)

H igh levels o f roving tw ist therefore always

represent p roduction losses and possib ly d raft

p roblems in the ring sp inning machine. O n the o ther

hand low tw ist can cause false d rafts o r even roving

breaks during bobbin winding.


Twist per inch:

The number of times the strand has

been twisted in one inch length. This is often

called as turns per inch and abbreviated as T.P.I.


The builder motion:

� This device has to perform 3 important tasks

during a winding operation:

1. Shift the cone belt corresponding to increase

in the bobbin diameter.

2. Reverse the direction of movement of bobbin

rail at the upper and lower ends of the lift

stroke.

Shorten the lift after each layer to form tapered

ends on the bobbins.


Roving frames F 15 / F 35:


Benefits of F 15 / F 35:

- Redesigned and more open machine concept for

better accessibility and therefore improved handling

- Up to 160 spindle positions with low space

requirement due to 110 mm gauge

- 6” and 7” bobbins possible

- Touch screen with 10” display

- Setting of all working parameters directly on the

panel

- ROJ - Electronic control of roving tension

- Roving ends down control with one photocell or

optionally with ROJ - optical sensors on each spindle

- Separate servo drives for flyers and spindles


Quality Data(For back process)

0.780.720.550.661.60CVm (3m)

1.300.910.600.891.95CVm (1m)

4.483.182.422.943.24CVm

3.562.541.912.342.58U%

RovingCombingFinisher

Drawing

Breaker

Drawing

CardParameters

role of drawing & combing

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