Presentation on forward feed &backward feed of combing

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

1. Presentation on 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: Feeding Nipping Combing Piecing Detaching

7. Combing Process:-

8. Combing Process:-

9. Feeding:- Lap is fed by Feed Roller. Type of Feed:

10. 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:- Feeding Detaching Cylinder Combing

11. 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

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

13. 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 .

14. 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

15. 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.

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. 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),

17. 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

18. 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.

19. Noil elimination theory for backward feeding:

20. 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.

21. 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

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

23. 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.

24. 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.

25. 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].

26. Index wheel:-

27. 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).

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). 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.

29. 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.

30. THANK YOU

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