Monday, 29 September 2008
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 The creel is a convenient rack for holding spools, cones or cheeses while the yarn is withdrawn to the warp beam.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.