Dyeing Hints

This site talks about very practical dyeing hints. Some of which are "animals are acidic and botanicals are basic", how to measure mordants and dyestuff, besides dyeing terminology.

FAQ in Cotton spinning-10

Q: what is the object of aprons.
Answer: The object of aprons is to contol the floating fibres to the possible extent and help to produce regular and stronger yarns with greater drafts.

Q. What is the importance of gap between the two aprons.
Answer: The aprons are not be too far apart or too close. Wider gap fails to control the floating fibre movement. If the gap is less, the pressure between the aprons more. The front-roller-gripped fibres suffer undue strain and the result is the formation of the defect known as 'crackers'

Q. What are the top roller cots or coverings. What is their importance.
Ans: the top rollers of draw frames, speed frames and ring frames, are made of metals. These are usually covered with a convenient cushioning material called as cots.

Q. What is the importance of the top roller cots.
Ans: These are needed to avoid the fibres getting crushed or damages, and also to give a proper grip on the fibres when they are being drafted.

Q. What are the requirements of a good cot.
Ans: A good cot is expected to have unifrom quality and performance, capable of being buffed to precise limits. It should have anti-lap up, oil-resistant, antistatic, trouble-free and temperature properties. It must possess good resilience in order to provide the required degree of cushion and must not contribute to end breaks.  It should withstand channeling action and any tendency for flute marding when top rollers are left standing under weight or pressure.

Q. What is the hardness of the cot. what is its importance.
Ans: A shore hardness of 60 deg to 90 deg is preferred. A harder surface would give rise to greater roller slip. A softer surface will lead to more roller lapping.

Q. Why top roll surfaces are grooved.
Ans: The object of grooving is to minimise the lap-up tendency, besides reduction of fly accumulation on top cleaners. The grooving also prevents surface distortions.

Q. What is the object of roller weighting.
Ans: In any pair or rollers, the bottom roller is positively driven while top roller is driven with the grip of the bottom roller. Normally the top rollers themselves fail to exert sufficient pressure and have to be assisted by some suitable external devices. Such devices are known as "roller-weighting devices"

Q. What is roller setting ? What is its importance ?
Ans: The distance between the centres of two pairs of rollers is called roller setting. If the pairs of rollers are set too wide apart, there will be plucking of the fibres instead of even attenuation, and the material that comes forward is full of thick and thin portions. On the other hand, if they are set too close, drafting becomes difficult and many of the long fibres get gripped by both the pairs momentarily. The fibres get either damaged or broken.

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.