Problems, Causes and Remedies of Combing Process

For getting high quality of yarn, one extra process is introduced which is called combing process. The combing process is carried out in order to improve the quality of the sliver coming out of the card. The process eliminates short fibers, it achieves better palatalization of fibers, it straightens curls, and it removes neps and residue impurities. So it play very important role for increasing the yarn strength.

Short fiber which we remove in combing is called comber noil. The comber noil can be recycled in the production of carded yarn. Yarn which is get from comber sliver is called comber yarn. Carded sliver are combine into comber lap in a single continuous process stage.
Combing machine
Main Problems/Defects in Combing Process:
  1. Inadequate removal of short fibers and neps
  2. Short term unevenness
  3. Hank variations
  4. Higher sliver breaks at coiler
  5. Frequent coiler tube choke-ups
  6. Web breakages at draw box
  7. Breakages at sliver table
  8. Breakages on comber heads
  9. Detaching roller lapping
  10. Excessive lap licking and splitting
Causes and Way of Remedies in Combing Faults:

Inadequate removal of short fibers and neps
Check head to head and comber to comber noil percent variations, and check the individual heads for web defects, such as uncombed portions due to slippage under feed roller, slippage of fibres under detaching rollers, plucking of fibres by half lap from nipper grip, web disturbance due to air currents due to defects in brush or/in aspirator. Check the machines thoroughly for bent and hooked needles on half lap and top comb, broken needles, nipper grip, feed roller grip, condition of detaching roller cots, condition of the gears driving bottom detaching rollers and damaged air seals in the aspirator box.

Short term unevenness
Prominent piecing waves, drafting waves, uneven fibre control due to worn out top roller cots in draw box, eccentric rollers in drafting / detaching field, play in draw box drive, high or low tension draft, and improper settings are the main reasons for short term variations in a combed sliver. Check U% and make use of spectrogram diagram to identify the source of the problem.

Hank variations
Single, double or uneven working of sliver on table due to improper selection of tension draft, rough surface of the sliver table, variation in the feeding lap, lap licking while unwinding, etc., are main reasons for variation in hank. If between comber variations are high, check the combers for variations in lap roller feed per nip, draft wheels on draw box, tension drafts at tables, draw box and coiler, and noil level variations.

Higher sliver breaks at coiler
Sliver guides with rough surfaces, coiler calendar rollers having eccentricity or jerky motion, high tension draft, improper balancing of sliver stop motion working on gravity principle, worn out gears, excess parallelisation of fibres in the sliver, improper condensation are the main reasons for sliver breaks. Check whether tension draft between draw box calendar roller and coiler calendar roller is too high causing stretching of sliver, or too low causing slackening of sliver. Check balancing of sliver break stop-motion and ensure that it presses against the sliver very lightly.

Frequent coiler tube choke-ups
If the coiler tubes are loaded with wax and trash, the sliver gets chocked. Clean the coiler tube with a rough rope. If cans are over filled, or the can spring is forcing the sliver to coiler plate, the choke up shall take place.

Web breakages at draw box
Burrs or accumulation of wax/trash particles at trumpet, too much spreading of web, defects in gear wheels, improper tension drafts are the main reasons for breakages in the draw box zone. In cases where the top rollers are buffed badly, the cottons shall stick to top rollers and lap.

Breakages at sliver table 
Waxy and rough surfaces of the table, improper tension drafts and piecing waves are the main reasons for breakages on the sliver table.

Breakages on comber heads
A tight or slack web, improper positioning of web trays, unclean web trays, burrs in calendar trumpets, improper calendar trumpet (heavy or light), improper functioning of clearer rollers in detaching section, piecing waves, and the trumpets set too away from the nip of calendar rollers are the main reasons for breaks at comber heads.

Detaching roller lapping
Rough or waxy surfaces on top roller cots, improper functioning of clearer rollers, too wide a setting of web guides are some of the reasons for lapping on detaching rollers. As the detaching top rollers tend to bend at the centre because of loading at both the ends, taper buffing is recommended.

Excessive lap licking and splitting 
Improper tension drafts and roller setting, excessive draft in the lap former, uneven lap and tight winding while lap preparation are the main reasons for lap licking and splitting.

Combers are very sensitive to changes in temperature and humidity, and hence it is essential to maintain the required temperature and humidity. In the majority of cases the bad working is attributed to fluctuations in temperature and humidity. 
  1. Training and development of technical staff in textile industry by B. Purushothama
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