Monday, June 19, 2017

Combing Process in Spinning

Comber and combing operation:
Comber is a machine by which fiber are combed and the action is called combing. The straightening and parallelization of fibers and the removal of short fibers and impurities by using combs, knives, brushes and rollers. One combed sliver is produced from eight lap.

Comber machine
Fig: Comber machine
Objects of combing:
  1. To remove a certain length of short fiber so that combed sliver is made by more long fiber.
  2. To remove neps and foreign material from carded fiber.
  3. To make fiber straight and parallel.
Necessity of combing:
  1. To produce finer or better yarn.
  2. To produce uniform yarn.
  3. To produce less thick, thin and hairiness yarn.
Why combing is necessary for finer yarn?
  1. For finer yarn count, high draft is required but draft irregularity for presence of short fiber. After combing short free product is ready for higher draft.
  2. Longer fibers are finer than short fibers.after combing higher count is possible to keep minimum no fiber in yarn dia. Ring spinning system at least 60-65 no of fiber. Rotor spinning system more than 80 no of fiber. If length increase then yarn dia decrease.
  3. Long fiber yarn has less hairiness but more luster.
  4. Combing is necessary for better yarn appearance and regularity.
  5. Less twist for finer yarn but more twist required in present of short fiber.
Contribution of combing to yarn quality:
  1. Improve the spinning value of fiber.
  2. Better twist distribution, which improve the strength of yarn.
  3. Improve uniformity, smooth and lusture of yarn.
  4. Reduce yarn hairiness and imperfection.
  5. Produce short trash free clear yarn.
Combing cycle:
Combing operation is done by cycle wise. Combing cycle or sequence of combing is point out below:

  1. Lap feeding by feed roller
  2. Lap nipping by the nipper
  3. Combing by the cylinder
  4. Nipper opening and forwarding
  5. Detaching roller backward movement
  6. Piecing
  7. Combing by the top comb
  8. Detaching roller forward movement
  9. Starting a new cycle
  10. Cleaning of cylinder comb
Combing operation
Fig: Combing operation
Noil: Noil is called the wastage of comber machine, which is constitute of short fiber, neps and impurities.

Degree of combing:

The amount of noil extracted during combing, which is expressed in percentages is called degree of combing. Degree of combing is depended on the short fiber presence in raw cotton, quality of yarn and end uses of yarn.

Types of combing:
Types of combing on the basis of degree of combing:

Half combing------------- upto 8% noil extraction
Ordinary combing --------- 9-15% noil extraction
Full combing ----------------- 16-18% noil extraction
Double combing ------------- 19-25% noil extraction

Factors of degree of combing or noil extraction:

1. Amount of short fiber in the raw cotton:
If the row cotton contains a huge amount of short fiber, a high degree of combing becomes necessary to get a high amount of noil extraction for good quality yarn.

2. Production quality: For good quality of yarn, the amount of noil should be present in limited range but passing if range of noil, not found of good quality yarn. Up to 25% noil, yarn strength, lusture are gradually increased but after that not increase of strength.

3. Production cost: Higher degree of combing removed higher noil% where production becomes slow at the same time the production cost become higher.

Main setting points of comber:

  1. Nipper and detaching roller.
  2. Cylinder needle and nipper
  3. Top comber gauge
  4. Brush setting
Effect of comber setting on noil extraction:

1. Effect of detaching setting: The distance between the leading edge of the feed plate and the nip of the detaching roller close setting for the same staple length will reduce the noil extraction% and vice versa. When the setting is wider for the particular type.

2. Effect of top comb setting:
The amount of waste extracted can also be adjusted by altering the position of top comb, combing operation will be proper and the noil extraction will be high. If it is set to the nippers, the waste extraction will be lower.

Characteristics of combed sliver:

  • Most of the fibers are long in combed sliver.
  • Fibers of combed sliver are straight and parallel of sliver axis.
  • Sliver has uniform weight per unit length.
  • No projected fiber at the surface of sliver.
  • Sliver is smooth and clean.
  • Sliver is free from trash and neps.
Efficiency of comber: 80-90%
Draft necessary at comber: 6-12
Production per comber: 50-150 Kg/hr/per delivery

Distinguish among card, draw and combed sliver:

Sliver type and properties
Fiber arrangement in sliver
Straight, parallel and oriented
Straight, parallel and oriented
Neps and trash
Very low
Depend on card or combed sliver
Short fiber
Very low
Depend on card or combed sliver
Sliver fineness (Ne)
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