FAQ in cotton Spinning-9

FAQs in Cotton Spinning

Q. What are the objects of ring spinning
Answer: There are three objects of ring spinning:
1. To draw the roving to the desired degree of fineness.
2. To impart sufficient twist to the emerging strand of fibres to from continuous yarn
3. To wind up the spun yarn into some convenient package form.

Q. What is the object of twist in Ring frame
Ans: The object of twist is to form a yarn with sufficient strength.

Q. Why every spinner wants to produce a yarn with as low twist as possible
Ans: Imparting twist consumes power, it also leads to low production. Also in untwisted from strength of yarn is about 30% more than in twisted state. Cloth manufactured bya low twist yarn tends to be fuller, stronger and more durable, Also dye absorption is better in low twisted yarns.

Q. How fiber length is related to twist
Ans: Longer the fiber, lesser is the amount of twist required. Frictional force increases with greater fibre length and as such there is more clinging power.

Q. How is fiber diameter is related to twist.
Answer: finer the fiber, more is the surface area available for clinging, thus more is the clinging power, hence lesser is the amount of twist required.

Q. How yarn diameter is related to twist ?
Ans: Coarser the yarn, more are the number of fibres per cross section and thus lesser is the required twist.

Q. How twist is related to yarn contraction ?
Ans: When twisted, the fibres take helical shape, that is, they get bent. Owing to this bending, there is a reduction in the length actually delivered from the front roller nip. This reduction in length is called contraction.

Q. What are the directions of twist ?
Ans: There are two popular ways in which yarn is twisted. Right Hand Twist is formed when the spindle revolves in clockwise direction as viewed from top. RH twist is also called, warp way, Z-way or twist way. The Left Hand twist is fromed when the spindle revolves in Anti clock wise direction. LHT is also called weft-way, S-way, reverse way etc.

Q. What are the various conventions of twist directions used in cloth.
Answer: A cloth is supposed to be best if woven with warp twisted right way and weft twisted left way.

Q. Why we avoid S-twist on ring frames.
Ans: It is often difficult to get left hand piecers to attend the machine with S-way twisting.

Q. Why over twisted yarn is not preferred ?
Answer: When overtwisted, the yarn becomes unbalanced. The yarn contracts excessively and becomes poor in strength. the yarn becomes hard, stiff and wiry. It has a harsh feel and dull appearance. It caused a lot of trouble in weaving.

Q. Why overtwisted yarns sometimes are needed.
Ans: Overtwisted yarns are manufactured for some special purpose. 'crepes' and 'voils' are woven with overtwisted yarns.

FAQ in cotton spinning-8

Comber

Q. What is a comber
Answer: Comber is a machine where short fibres below a certain predetermined length can be easily separated out.

Q. What are the objects of combing
Ans: After combing the fibres are more or less uniform, well straightened or parallelised and free of neps and particles of trash that escaped carding.

Q. What will happen if carded material is presented as such to comber.
Ans: Majority of the fibre hooks in a carded sliver are trailing. Hooks can be straightened out by comber needles provided they are presented in leading position. If the trailing hooks are presented as such, they behave like short fibres and escape into noil.

Q. How we can make majority hooks (trailing) from card sliver to present as leading hooks to comber.
Ans: In order to make the major hooks take the leading position, there should be even passages or even reversals between the card and the comber.

Q. What is lap preparation for comber
Ans: 'Lap preparation' can be taken as a general term which includes all the passages between the card and the comber.

Q. What is backward feed
Ans: On conventional combers the feed usually takes place when the nippers are going backwards. This is known as backward feed.

FAQ in Cotton Spinning-7

Q: What is the object of a speed frame
Ans: The object of a speed frame process is to reduce the sliver bulk to a diameter suitable enough fro the ring spinning frame to spin yarn.

Q : Why twist is required at the speed frame
Answer: Minimum twist is required to see that 1. The roving comes from the front roller nip on to bobbin through the flyer bore without being broken. b. The roving is nicely wound on to the bobbin. 3. that it does not suffer any creel stretch during unwinding in the next machine creel.
4. that the next machine can easily break the twist in the break draft zone.

Q. What is the function of paddle.
Ans: the paddle helps to produce compact and regularly built bobbins.

Q. How come the paddle always keeps pressed against the bobbin.
Answer: The paddle always keeps pressed against the bobbin due to the centrifugal force of the vertical solid bar.

Q. Why the threading slot is in the curved form.
Answer: This helps to prevent air drafts from entering the tube and disturbing the roving inside it. Besides it prevents liberation of fly.

Q: What causes winding of the twisted roving on the bobbin.
Ans: The differential surface speed between presser paddle and bobbin surface are responsible for winding of the twisted roving on the bobbin. Which is caused by differences in the flyer speed and bobbin speed.

Q: Why bobbin speed is reduced as the package diameter increases
Ans: As the diameter grows, bobbin surface speed increases although the revolutions per minute is constant. Therefore, bobbin speed is reduced in order to maintain the constant difference between the speeds of bobbin surface and paddle.

Q: What is 'flyer leading' and 'bobbin leading' case. Which is used in existing Speed frames.
Answer: S/F in which the flyer speed is higher than the bobbin surface speed is called 'flyer leading'. S/F in which the bobbin speed is higher than the flyer speed is called 'bobbin leading'. 'Bobbin Leading' case is used in existing S/F.

FAQ in Cotton Spinning -6

FAQ in Cotton Spinning-6

Q. What type of hooks are there in the card web ?
Answer: Bulk of the fibres in the card web are found to have hooks at their rear ends, and they are termed as trailing hooks.

Q. What type of hooks are removed at the drawframes.
Answer: Hooks are preferentially removed when they are presented in the drafting field in trailing direction.

Q. What is doubling. How does this affect regularity of a sliver.
Answer: Doubling is feeding more slivers together into the drafting zone. It improves the uniformity of sliver.

Q. Why we cannot offer a high draft in one go.
Ans: The resistance offered by the disorderly state often results in a greater unevenness in the drawing material.

Q. What can be the drawbacks of excessive parallelisation.
Ans: Slivers with high parallelisation become soft and their withdrawl from cans at later stages results in excessive creel breakages.

Q. What is roller slip
Ans: Top rollers are no positively driven. They are made to bear against the bottom fluted rollers with a suitable weighting arrangement. The motion transmission to the top roller is through the bulky sheet of fibres. Thus the speed of top roll is not the same as botton roll. This fall in speed of top roller is termed as roller slip.

Q. what will happen due to roller slip
Answer: The roller slip produces characteristic drafting waves or unevenness characeristics.

Q. What is a drafting wave
Answer: The irregular motion of short fibres between pairs of rollers give rise to a wave like formation that is known as drafting wave.

Q. What is the principle applied in roller setting over 44 drafting system.
Answer:
Front and second pair= effective length + 1/8 "
2nd and Third pair= eL+ 1/8"+1/8"
3rd and Back Pair= eL+1/8"+1/8"+1/8"