Forward & backward feeding process and it"s impact on the quality of extracted sliver & noil.

1. g
Forward & Backward Feeding
Of Coming Process

2. What is Combing:-

3. What is Combing:-
Combing is a process by which quality of short fibers and remnant
fragments of impurities present in a carded or drawn sliver are minimized,
improves yarn strength , evenness etc to give a clean sliver with the vast
majority of constituent fibers in a straightened and parallel state.
A good lap fed to the comber should have:-

4. What is Combing:
Combing is a process by which quality of short fibers and remnant
fragments of impurities present in a carded or drawn sliver are minimized,
improves yarn strength , evenness etc to give a clean sliver with the vast
majority of constituent fibers in a straightened and parallel state.
A good lap fed to the comber should have:-
 Highest degree of evenness so that lap is gripped uniformly by the nipper
 A good parallel disposition of fibres so that long fibres will not be lost in the
noil
 Trailing hooks from carding should be fed as leading hooks to reduce long
fibre loss in the noil
 Degree of parallelisation of lap fed to the combers should be optimum

5. Process Sequences of Combing process:

6. Important Terms:
1. Feeding
2. Nipping
3. Combing
4. Piecing
5. Detaching

7. Combing Process:-

8. Combing Process:-

10. Feeding:- Lap is fed by Feed Roller.
Type of Feed:
Feed
Forward feed
or Concurrent
feed
Backward Feed
or Counter or
Reverse Feed

11. Forward(Concurrent) Feed:
The feeding of the sheet into the nippers occurs while the nipper are moved toward the detaching
rollers termed as Forward Feeding or Concurrent Feeding.
 Forward feed has been chosen for higher production rate when quality requirement is not
rigorous with noil % of 5-12%
Process Sequences:-
FeedingDetaching
Cylinder
Combing

12. Backward (Counter) Feed:
The feeding of sheet or lap into the nippers occurs during the returning of the nipper termed as
Backward or Counter feeding.
 Backward feed is selected for the higher quality grades requirements with noil % of 12 to
25%.
Process Sequences:-
Detaching
Cylinder
Combing
Feeding

13. What is noil%?
Noil percentage is the ratio of Noil weight to the total
wt of sliver and noil.

14. What is noil%?
Noil percentage is the ratio of Noil weight to the total
wt of sliver and noil.
In overall spinning process combing operation serves to
improve raw material quality by removing noil. The extraction
of noil has directly affected on cost, it is not possible to
increase noil beyond certain limit. From both economical and
quality point of view selection of optimum level of noil
extraction is necessary. Keeping this view in mind an attempt
has been made to reduce nep level in combing process by
adjusting the noil percentage, and to get improvement in yarn
quality.

15. Noil Elimination Theory For Forward Feeding:
After the detaching stage has been completed,
all fibers longer than E have been carried away
with the combed sliver.
During the combing cycle all fibers shorter
than E pass into the noil;
Feed occurs during the subsequent forward
stroke of the nippers, during which the fringe
is increased in length by the distance S. During
detaching stage, the detaching rollers take at
least all fibers longer than E into the combed
sliver because they are caught by nip point of
detaching roller. However, as feeding occurs
at this stage, fibers b of the original length
(E - S), i.e. shorter than E are now moved
forward to the nip line of detaching roller since

16. Noil Elimination Theory For Forward Feeding:
feeding occurred by distance S. That is why
fibers longer than (E - S) are also now
carried away into the combed sliver.

17. Noil Elimination Theory For Forward Feeding:
feeding occurred by distance S. That is why
fibers longer than (E - S) are also now
carried away into the combed sliver.
 In the combing cycle all fibers shorter
than E pass into the noil, this is represented
in by the area qBr.
 The fibers longer than (E - S) are carried
away into the combed sliver, the combed
sliver represented by the area- trapezium
AmnC
 The figure qmnr can be divided according to
the mean fiber length by the line op (E -
S/2),

18. Noil Elimination Theory For Forward Feeding:
 Since in similar triangles the
areas are in the same ratio as
the squares of the sides, and
since the noil percentage is
based on the ratio of weight
of waste to weight of
feedstock.
 The following relationship
can be assumed:
 p%=(oBp/ABC)×100
=(op²/AC²)×100
=[(E-S/2)²/M²]×100
 p = noil percentage

19. Noil elimination theory for backward feeding:
 During the detaching stage the distance
between nippers to the detaching rollers is
E, the detaching rollers draw off all fibers
longer than E caught at the nip point.
 As the nippers moves backward, the
feed roller feed fiber fringe S.
 The fringe projecting from the nippers
is now E + S.
 All fibers shorter than (E + S) are
carried away by the circular combs
because they are not clamped. They pass
into the noil.
 All the fibers longer than E are act as a
combed sliver.

20. Noil elimination theory for backward feeding:

21. Noil elimination theory for backward feeding:
 In this diagram all fibers to the
right of the line r-q are combed out
into the noil represented (area rqB).
 In the region rqmn it is therefore a
matter of chance whether the
fibers remain in the sliver or pass
into the noil. Accordingly, a
division can be made based on the
mean fiber length represented
within this area.
 It can be assumed that the
trapezium AopC represents fibers
transferred to the combed sliver
 The triangle oBp represents those
passing into the noil.
 The dividing line between these
areas has length (E + S)/2.

22. Noil elimination theory for backward feeding:
 The dividing line between these areas
has length E + S/2. Since in similar
triangles the areas are in the same ratio
as the squares of the sides, and since
the noil percentage is based on the
ratio of weight of waste to weight of
feedstock.
 The following relationship can be
assumed:
p%=(oBp/ABC)×100
=(op²/AC²)×100
=[(E+S/2)²/M²]×100
p = noil percentage

23. Influencing parameter of noil %:
 Cylinder Combing
 Feed Length
Detaching Length
 Needles of the Top comb

24. The quality of Combing Operation in Forward & Backward Feeding:
 With forward feed not only will shorter fibers be passed into the combed sliver ,but
also the quality of combing operation itself must be different.
 A fiber having trailing end laying just in the bite of nippers ,during the forward
movement of nippers ,with Forward Feed this fiber passes into the combed web
without any change ,because the feed roller pushes it out of the nippers.
 In the backward feed of combing ,this fibre will stay in the feedstock ,because no
feeding occurs during forward movement of the combs ;the fiber is then nipped
while projecting with the hook inside the nippers and combed once again
- Therefore, if backward feed is used ,circular combs rake through the fibers
more often ,so the quality of the combing operation is increased.

25. Index Wheel:-
 Combing process consists of a series of operations
 The operation must occur in a specific sequence/order
 Each operation must begin and end without creating any interference with other .
 Index wheel helps setting of machine elements corresponding to various operation.It
is mounted on cylinder comb shaft.
 The wheel has 40 graduation marks on its periphery.
Forward & Backward journey times of Nippers:
More time is to be given for forward journey as it reduces velocity of the nipper
assembly and there by air drag on combed fringe of fibers approaching the
detaching rollers.
A 60:40 ratio is chosen .
Therefore ,
Forward journey timings= .6*40=24 index no.
Backward journey timings= .4*40=16 index no.

26. Forward feed:-
 Feeding should be completed during forward osscilation of nippers i.e. 0 to
24.
 Nipper should remain in an opened state during feeding[i.e 10+2 to 34-2 or
12 to 32
Backward feed:-
 Feeding should be completed during backward oscillation of nippers 24 to
40/0.
 Nipper should remain in an opened state during feeding that is in between
12 to 32.
 Feeding should end prior to commencement of cylinder combing process
[<35].

27. Index wheel:-

28. Impact on quality of Extracted Sliver & Noil:-
 In cotton spinning mills, generally combing is carried out to improve the quality of sliver
obtained from the card, by eliminating short immature fies and impurities in order to spun
quality yarn out of it. The effect of combing depends on the type of feed and feed length. In the
present study, the quality of combed sliver and noil extracted in backward feed & forward feed
has been studied by analyzing the quality of combed sliver and noil using the latest Advanced
Fie Information System (AFIS PRO2).

29. Impact on quality of Extracted Sliver & Noil:
 In cotton spinning mills, generally combing is carried out to improve the quality of
sliver obtained from the card, by eliminating short immature fies and impurities in
order to spun quality yarn out of it. The effect of combing depends on the type of
feed and feed length. In the present study, the quality of combed sliver and noil
extracted in backward feed & forward feed has been studied by analyzing the quality
of combed sliver and noil using the latest Advanced Fie Information System (AFIS
PRO2).
 The results clearly indicate that for a definite length of detaching distance, the short
fie removed is higher in backward feed compared to forward feed and thereby an
improvement in AFIS 5 % length (up to 3.5%) compared to forward feed (2.0%) due
to more combing action because of short feed length. Further there is a good
improvement in maturity, reduction in nep count & trash in backward feed compared
to forward feed. This study will be more useful for the spinner to select a right type
of feed in combing to achieve a desired quality with a minimum of loss of fiber in
combing.

30. Comparison between Forward & Backward feed:-
Parameter FORWARD FEED BACKWARD FEED
Nipper
Movement
Forward feed for forward of
nippers .Forward feeding
occurs when nippers are
moved toward to detaching
rollers.
Backward feed for backward
of nippers. It is occurs when
nippers moves away from
detaching roller.
Production rate It is selected for higher
production rate.
Production rate in
backward feeding process is
lower than the forward
feeding system.
Noil % Noil extraction % is low.
5%-12%
Noil extraction % is high .
12%-25%.
Quality It gives lower quality
combed sliver than the
backward feed.
It gives higher quality
combed sliver than the
forward feed.
Combing action Combing action done by top
comb is less good.
Journey times of nippers for
forward feed is more.
Combing action done by top
comb is more good.
Journey times of nippers for
backward feed is less.

31. THANK YOU

32. Presented by
Name - Katha Mahanty.
Roll no. – 11101417027.