Tuesday, 14 October 2008

Control of Size Pick-up

Control of size pickup

For control on variation of size pick up , the two steps required are:

a. determination of average size pick up on the beam
b. Suitable adjustment in sizing conditions

a. Determination of average size pick-up

Example: The weight of sized yarn on a beam was found to be 82.5 lbs. The beam contains 1050 yards of warp, whose count before sizing was 50s cotton.If the number of ends in the warp is 3000, calculate the following:
a. The weight of size on the yarn
b. The % of size put on the yarn
c. The count of sized yarn

a. Weight of size on warp= weight of sized warp- weight of same length of unsized warp

Now weight of unsized warp= (No of ends x length of warp in yds)/(count of unsized yarn x 840)= (3000x1050)/(50x840) = 75 lbs

Therefore weight of size on warp = 82.5 -75 = 7.5 lbs

b. Percentage of size on warp = (wt of size x 100)/ wt of unsized warp

= (7.5x1000)/75 = 10%

c. Count of sized yarn = (No of ends of the warp x length of warp in yds)/(wt of lbs of warp x 840) = (3000x1050)/(82.5x840)= 45.5s cotton

b. Control on sizing condition

1. Viscosity of size paste in size box: Any variation in the concentration or temperature alters the viscosity of the paste which in turn affects both the level of size pick up and extent of penetration. Initially as the viscosity increases, the size pick-up also increases. But as the viscosity increases beyond a point, the size pick up is reduced.

2. Sqeezing pressure and condition of squeezing nip: The squeesing pressure determines the extent of penetration of the size paste between the fibres of the yarn and also of the removal of excess size paste and hence the level of the size pick up.

3. Speed of the sizing machine: Other sizing conditions remaining unchanged, the size pick up increases with increasing sizing speed and vice versa. This is because the time available to squeeze the surplus size from the yarn is less at high speeds.

4. Depth of immersion roller in size paste: the depth of immersion roller in the paste determines the duration for which the yarn remains immersed in the paste. this duration in turn influences both the level of size pick up and the extent of size penetration.

5. Level of size paste in the size box: Variation in the level of size paste is an important source of size pick-up variations both within and between beams.

6. Density of ends: When the density of ends is high, difficulties are encountered in obtaining adequate and uniform size penetration. Therefore size pick up may vary at these fabrics.

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