Friday, 3 October 2008
control of end breaks in warping
Minimising end breaks in warping involves four steps namely:
1. Control of tension in the yarn
2. Satisfactory maintenance of those machines
3. Minimising the defects on packages produced at winding
4. A regular check on the end breakage rate for comparison with the norm.
1. conrol of tension in the yarn
On the warping machine, there are two types of variation in yarn tension
1. Between different stages of unwinding of a package. This can be detected after the first thread guide.
2. Between ends. It can be detected at the head stock.
The tension variation that occurs during the unwinding of a package can be minimised if you design the creel such that the distance between the package and the first thread guide is shortest, it will avoid the yarn balloon rubbing the nose of the package.
The tension variation between the ends at the headstock is minimised if the groups of neighbouring ends on the beam are taken from the same column of packages in the creel.
2. Condition of Machine
a. Alignment of the package at the creel
Non alignment of the creel package with respect to the first guide is often seen to be a cause of high end breakage rate at warping. This alignment is done with the help of a gauge.
b. Eccentric Guide rollers
On machines with mechanical stop motions, there are several guide rollers at the headstock which are positioned very near to one another. Eccentricity in those rollers can introduce short term tension variations of high amplitude.
c. Thread Guides
Deep cuts in thread guides can significantly increase yarn tension and hence deteriorate warping performance. If found dirty, the thread guides should be cleaned with CCl4.
d. Relative humidity and temperature
For satisfactory working at warping, about 60% RH should be maintained. The dry bulb temperature should be kept at about 29 o C (84 o F). Lower humidity may increase yarn hairiness, end breaks and liberation of fluff. The fluff ultimately passes to the beam and given difficulty during sizing. Higher humidity is unnecessary; in fact relative humidity higher than 70% may increase end breakage rate.