Process Control in Warping-1

Process Control in Warping

Warping is the process of winding together on a beam a specified number of warp ends from Creel. The creel is a convenient rack for holding spools, cones or cheeses while the yarn is withdrawn to the warp beam.

The following are the process control parameters in a warping department:

1. Minimising End breaks.
2. Quality of warping beam
3. Control of productivity

Importance of Minimising end breaks:

The stoppage of the machine due to an end break is likely to deteriorate the quality of the beam due to three reasons:

1. The rubbing of the beam by the drum which stops abruptly.
2. Owing to the difficulty in finding the broken end, there is a possibility of incorrect mending. It may lead to lappers during sizing.
3. There is some loss in the extensibility of broken end when the machine is stopped, it increases the probability of breakage in weaving and sizing.

The following points should be noted to improve the quality of warping beams:

1. condition of beam flanges:

If the beam flanges are damaged, the unwinding of yarn near the flanges will not be satisfactory. This will cause difficulties in sizing and weaving.

2. Stop Motions and Breaks:

Proper stopping of the warping machine after an end break ensures that the broken end on the beam can be traced easily.

3. condition of the driving drum:

On most warping machines the beam is driven by fricitonal contact with the driving drum. In order to get a package of the correct density, the pressure between the drum and the warper's beam has to be kept at fairly high level.

4. Barrel Diameter of the Beam

Beams of small barrel diameter give rise to high unwinding tension at sizing, particularly when the beam is about to become empty.

5. Cuts in Accessories in the path of yarn

Drop pins of stop motion, guide rollers, reed denting etc. should bot have any grooves.

6. Creel Fans

Fluff accumulated on the machine, particularly at thread guides, causes tension variations in the yarn. This fluff can pass on to the beam.

7. Length Measuring Motion

The length measuring motion should be accurate, otherwise estimation of beam count would be wrong and subsequently will give incorrect values of size percent which is commonly determined from the weights of yarns on the warper's and the size beams.

8. Density of the Beam

The beam should be firm, inadequate pressure between the beam and the drum causes soft beam. Adequate pressure should be maintained by making suitable mechanical adjustments.

Control of Productivity

The productivity at warping depends upon the machine efficiency and machine speeds. The speed is governed by the mechanical condition of the machine and its design. Machine efficiency depends on several factors, such as the breakage rate, the time taken to mend the machine stop, set length, length of yarn on supply package etc.

FAQ in cotton Spinning-11

Q: Why cotton system of spinning is called so ?
Ans: Because it was initially developed for spinning cotton fibres.

Q: How fiber length affects spinning ?
Ans: A longer fiber can be spun to a finer counts and gives a better spinning performance. In general, the longer the fiber, the higher the yarn tenacity. Too long a fiber gives processing problems specially in carding. Productivity also increases because the yarn spun from a longer fiber needs a lower twist.

Q: What should be the min. number of fibres in the yarn cross section for better spinning performance.
Ans: It should be around 85 for 38 mm and 68 for 51mm fibre

Q: How finer fiber affects spinning performance.
Ans: A fiber fiber can allow spinning of finer yarns. It also leads to more even yarns. Also low twist is required because of greater interfiber friction. However it can lead to excessive neps at carding.

Q: How finer fiber affects the fabric.
Ans: Fabrics produced from finer fibers drape better. They also have a soft "sheen". It usually produces softer fabrics.

Q: What is the formula to calculate the number of fibres in a yarn cross section.
Ans: N = (5315/fiber denier)/ yarn count (Ne)

Q: What is the min fiber strength needed for spinning ?
Ans:0.6 to 0.7 grams/denier

Q: What is crimp. How does it affect spinning.
Ans: It is defined as the weaviness of a fiber. It increases the interfiber friction which helps in spinning process. It also produces yarns and fabrics haveing a greater bulk and a softer feel.

Q: How crimp is measured.
Ans: Crimp is measured in arcs/inch

Q: What will happen if crimp is lower? If crimp is higher ?
Ans: A lower level of crimp than recommended can lead to problems such as  lap licking, higher cylinder loading, card web breaking and roller lapping. A higher level of crimp will lead to excessive neps.

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.