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Control of waste in comber
The primary functions of a comber are three:
Remove fiber hooks and parallelize the fibers
Bring about fiber-to-fiber separation
Remove short fibers.
The comber waste also contains a large number of neps and some foreign matter particles.
Combing, therefore, results in a considerable reduction of nep content and in some cleaning of cotton also.
However, a higher percentage of waste need not always mean more removal of short fibers and neps.
The high cost of removing even one percent extra comber waste makes it imperative that a mill should carefully choose the optimum level of comber waste for each mixing.
Then exercise a strict control on all combers to maintain the waste at the desired level.
For an effective control of short fibers, retention of long fibers and removal of neps, the following considerations are important.
The card trailing hooks are longer and more numerous than the leading hooks. They are removed when fed as leading hooks by keeping an even number of reversals between card and comber.
The waste at comber can be reduced by increasing precomber draft upto certain limit without effecting the resultant yarn quality.
The proper place for controlling neps is carding and not combing. It is often more economical to run card at somewhat low production rate than to take out extra comber waste.
The minimum level of comber waste which gives the desired Yarn quality, Yarn appearance and End breaks at ring frame depend on nature of fiber length distribution in the cotton or mixing.
Nature of fiber length distribution of mixing
Short fiber %
(by number)
Mean length Approximate level of comber waste %
(by weight)
Triangular >20% 26mm No optimum
(waste%~quality)
Flat <18% 26mm 0.5*S.F%
Experience based information obtained by ATIRA in this regard is summarized as under:
An increase in comber waste results in improvement in yarn quality till most fibers below 15mm length are removed.
For e.g. for a cotton with short fiber content of 22%, one can take trials with 10%, 11% and 12%.
The minimum level which gives the desired yarn quality and minimum end breakage rate in spinning gives should be adopted for large scale production.
ROUTINE CHECK OF COMBER WASTE
The waste at comber need to be checked and controlled due to the following reasons.
More waste than the nominal means financial loss.
Less waste than the nominal could lead to unacceptable yarn quality performance.
Between comber waste variation could contribute to between lea count variation.
The numerous experiments conducted in the industry have brought out the following facts.
Head waste CV exceeding 6% calls for attention.
. Comber waste CV in excess of 4% calls for attention.
. For a well set and maintained comber , the difference in the level of comber should not exceed 3% from the average.
PROCEDURE FOR DETERMINING COMBER WASTE
Remove noil from the back of each head and break the sliver just beyond the coiler.
Collect head wise noils and comber sliver from the can by breaking just after the coiler.
The overall comber waste and head wise waste are then calculated as follows:
Wt. of noils from all heads * 100 Overall comber waste (%) = ........................................................... (Wt. of sliver+Wt. of noil from all heads)
Wt. of noil from a head *100 Head wise waste (%) = ............................................... 1/n (Wt.of sliver+Wt.of noil from all heads)
Feed rollers move the lap by 4-6.5 mm .
Upper nipper plate Z 0 is lowered and the fibers are nipped
Combing segment k combs the fiber fringe and Carries away those fibers not held by nippers
Nippers open again and move towards the detaching rollers.
Detaching rollers rotate backwards and bring back a part of the material
The new fiber (B) fringe is placed over the returned material (V)
Detaching rollers reverse the direction and draw the clamped fibers out of sheet W.
The top comb thrusts its single row of needles into the fibe fringe.
Nipper assembly moves back. Top comb is withdrawn and new cycle begins. Combing segment is cleaned by the brush roller.
