FAQ in cotton spinning-4

FAQs in Cotton Spinning
Q. Discuss about the feed rolls used in opening machine with given headings.
(i) Definition, (ii) Construction, (iii) Fundamental, and, (iv) Types of feeding
Q. Define the beater in opening machine.
Q. What are the objects of beater?
Q. Express the drafts and their calculation. What is the difference between the actual draft and mechanical draft?
Q. What are the objects of carding? How are these objects fulfilled
Q. What is meant by card clothing? With a neat sketch show the parts of a card clothing.
Q. What is meant by neps in carding?
Q. Mention and briefly explain the factors in judging the quality of carding.
Q. What are the effects of doubling
Q. Explain about the function of drawing rolls used in drawing frame.
Q. What is meant by cotton combing?
Q. What are the objects of combing? Explain briefly how these objects are fulfilled.
Q. List the various yarn characteristics improved by combing.

Please see the answers to these questions here

FAQ in cotton Spinning-3

FAQ in cotton spinning-3

Q: What are condensers, what is their role ?
Answer: These are perforated cage rollers. They supply a current of air at a high velocity, convey the cotton uniformly from stage to stage and incidently, perform a bit of cleaning by carrying away the floating dust, impurities and short fibres to a separate collection centre.

Q. What is difference between the conventional and the modern blow room lines.
Answer: Modern blowroom lines have more opening points and fewer beating points.

Q. What is the object of carding.
Answer: The objects of carding are three:
1. To open out thoroughly the tiny lumps so that every fibre becomes individualised and the cotton is no more in an entangled state.
2. To remove all impurities, neps, short fibres etc. which have escaped the blowroom action.
3. To prepare the well cleaned material into a compact sliver form and lay into containers for subsequent processes.

Q. Name the three major regions where cleaning takes place.
Answer: Taker-in and flats.

Q. What are the constituents of flat strips.
Answer: The flat strips are mostly short fibres with some of the impurities like kitty leaf bits etc.

Q. Why speed of licker-in is kept less for longer staples.
Answer: Longer fibres are held for longer time by the bite of the feed roller after the licker-in starts working on them. As a result more teeth act on the fringe of the fibres and there is every chance of fibres getting damaged.

Q. What is back plate. What is its function.
Answer: This ia a curved plate covering the cylinder just above the licker-in and its main function is to keep the fibre bunches delivered by licker-in, remain on the cylinder wire till they are taken by the flats. This also helps to prevent the development of undesirable air currents.

Q. What is front plate. What are its purposes. Why it is called percentage plate.
Answer: This is a plate similar to back plate and is fitted at the front just above the front door. This has a three fold purpose namely:
1. To keep the cylinder surface covered in order to prevent the fibres from flying off.
2. To keep all other material away from cylinder.
3. To provide the opening for stripping and grinding the cylinder.

It is known in America as 'percentage plate' as its adjustment helps to regulate the quantity of flat strips.

FAQs in cotton Spinning-2

FAQs in Cotton Spinning

Question: What are the causes of Cotton Fibre degradation

Light in the presence of moisture has a degrading effect on cotton fibres. Heat also affects strength, stretch and life of cotton.

Q: What are neps. How they are formed

Neps are fine specks in the form of tiny balls of entangled fibres. They are formed due to bad mechanical processing conditions. Longer and immature cottons are more prone to neppiness.

Q: What are naps. Hw they are different from neps


Naps contain fibres whcih are entangled together, but much more loosly than those in neps. A nap can open out while it is not possible to open out a nep.

Q. What is the necessity of a blowroom.

Textile mills are generally located far away from the fields where cotton is grown. Therefore, compressing loose cotton into a compact bale form is unavoidable for economic transportation. This cotton has to be opened in the blowroom.

Also during picking and ginning quite a number of impurities get associated with such cotton, to remove all such impurities from the cotton, blowroom sequence of machines is quite necessary.

Q. Why there are so many machines in the blowroom sequence

The real work of opening, cleaning and blending is done by the blowroom machines. The action of opening and cleaning should be gradual. Therefore, a number of machines are required which gradually open and clean the cotton. The machines in the beginning of the line are mostly expected to reduce the lump size, and the latter machines are expected to open out or still reduce the size of fringes or tufts.

Q. What are lattices in blow room line, what is their purpose

Lattices are made up of wooden legs which are either plain or spiked. Horizontally arranged lattices are mostly plain while spiked ones are meant for lifting purposes. They help to move the cotton ahead in regular and uniform quantities.

Q. What is the purpose of beaters.

The object of beating is to shake out the impurities and force them through specially arranged gridbars and perforated sheets.

Q. Why a three bladed beater is better than a two bladed beater

It is heavier in weight and each blow is more forcible than a two bladed beater. Besides, it gives 50% more beats, which means that this can be run at a lower speed than a two bladed beater and incidently reduces vibrations, wear and tear in the machine.

Introduction to textile sizing

Necessity of Warp Sizing
During the weaving process, the yarns are subjected to three basic physical stresses. These are stretch, strain and abrasion. Although these forces exist in varyiing proportions depending upon the type of loom and the fabric styling,all three are forces that must be considered in all cases.Therefore, the ideal sizing material would produce a smooth, tough, elastic film which would adhere to the yarn. It should smooth to friction and abrasion. It should be tough to endure the load or strain and it should be elastic to allow flexibility and sufficient stretch.

Advantage of using Polyvinyl Alcohol in Warp Sizing

PVA is an excellent film provider. Its tough film is easily removed (desized) with hot water. It leads to the following benefits:

-Superior Abrasion resistance
- Adhesion to synthetic fibres
-flexibility/ elongation
-strength
- user friendly slashing performance.

Yarn sized with PVA can run at lower add-on because of the adhesion and strength advantage PVA provides over natural binders. It requires in quantity only 1/3 rd of the starch.

The excellent abrasion resistance means less shedding on the slasher and in the weave room.

The inherent flexibility of films of PVA resins eliminates the need for high Relative humidity in the weave room. A RH of 65-75% are recommended

PVA solutions are thermally stable and can be maintained for lower periods of time at high temperature.

PVA are widely reclaimed and reused for sizing, thus reducing effluent levels from the finishing plant.

PVA and wax together will provide the optimal size performance. Wax is needed to reduce dryer can sticking, weaker film for easier split, minimize clinging on looms and improved lubrication for the size coating. However, excessive use of waxes can lead to poor adhesion, brittleness, roughness and decreased abrasion resistance. Also waxes can be difficult to remove at desizing stage which can lead to quality problems in desized fabrics. It is important to select a wax that contains an effective emulsifier. It will act to prevent wax from redepositing back on the fabric during desizing. Common wax is tallow.

Starch is primarily used as an extender for PVA to reduce formulation cost. However antistats are needed with starch containing formulations to minimize static on warp yarns. Generally they are not needed with 100% PVA sizes. Antistats funciton as humectants, helping to retain moisture in the film while simulatneously plasticising the film. It includes urea, ethylene glycol and glycerol. Recommended level is 3-7%.

Defomers: Size solution can exhibit foam. For this we need defoamers in the levels of 0.25 to 1.00% based on the weight.

Binders- They are used for synthetic fibres- two major types are polyester or polyacrylic solution.

To avoid lappets warp density: For ring Spun 100% cotton - Spacing between adjecent ends should not be less than the diameter of the yarn. For Ring spun P/C blend spacing should not be less than 1.5 times the yarn diameter. For open end yarns, number of yarns per inch should be 10% less than the ring spun yarns of comparable count.

Viscosity: A properly sized warp will have completely encapsulating (360o) the yarn surface to hold down loose fibres. Internal penetration must be sufficient (15-25%) to anchor the size film to the surface of the yarn. Too low a size viscosity allows liquid to penetrate too deeply into the yarn. Too high a viscosity will not allow sufficient penetration to anchor the size. If ends are tightly packed in the size box, viscosity should be lowered to improve penetration.

Temperature of the size box is important for the right viscosity. High temperature may cause PVA to form skin- causing hard size formation when the slasher is stopped. Recommended temperature is 160-185 o F.

Drying can temperature should be set at the minimum to dry the yarn to hte desired moisture content of 5-8%.

Yarn stretch in cotton should be 1-6%, PC should be 1-1.5%, and Rayon/ Acrylic should be 3-5%.

Desizing agents: Can be water for PVA, NaoH for oils/waxes, HCL for starch, Enzyme for starch, Solvents for oils/waxes or peroxide for PVA.

For more details about textile sizing please click here.