Combing Process

Sequence of Operation in A Comber

For getting high quality of yarn, one extra process is introduced which is called combing process. Combing is an operation in which dirt and short fibers are removed from sliver lap by following ways:

1. Feeding, lap is fed by feed roller
2. Fed lap gripped by the nipper
3. Gripped lap is combed by circular comb
4. Detaching roller grips the combed lap and moves forward
5. While the detaching roller delivers the material, top comb comes into action to further clean the lap
6. While going back, nipper opens and receives a new bit of lap

The raw material delivered by the carding machine can not be fed directly to the comber. Lap preparation is a must.

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

Types of feeds in Comber

Forward feed (concurrent feed):

Feed of the sheet into the nippers occurs while the nippers move towards the detaching roller.

Backward feed (counter-feed):

Feed of the sheet occurs during return of the nippers. Higher Noil % always improves the imperfections in the final yarn. But the strength and other quality parameters improve upto certain noil %, further increase in noil results in quality deterioration. In backward feed, the cylinder comb combs through the fibres more often than in forward feed. Therefore, the elimination of impurities and neps is always good. However the difference is usually undetectable in modern high performance combers of the latest generation.

The Feed Length has a direct influence on production rate, noil %, and the quality of combing. High feed length increases the production rate but cause deterioration in quality. Higher the quality requirement, feed length should be lower. To some extent , the feed length may be decided by the length of the fibre also.

Detaching length is the distance between the bite of the nippers and the nip of the detaching rollers. This distance directly affects the noil %. More the detaching distance, higher the elimination of noil.

Needles of the top comb have a flattened cross section and are used with a point density in the range of 22 to 32 needles per centimeter. More the needles, more the noil%. The Depth of Penetration of top comb also affects the Noil %. If the comb depth is increased by 0.5mm, approximately 2% increase in noil will occur. When the depth is increased , the main improvement in quality is seen in Neps. Over deep penetration of top comb disturbs fibre movement during piecing which will deteriorate the quality.

Production Calculation of the comber

• N- Nips per min
• S- feed in mm/nip
• G- lap weight in g/m
• K- Noil percentage
• A- tension draft between lap and feed roller(from 1.05 to 1.1)
• E- efficiency

Production = (E * N * S * G * (100-K) * 60 * 8) / (1000 * 1000 * A *100)