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Monday, May 6, 2019
Friends, before discussing about sizing calculations, we will discuss about sizing process in brief.
Objectives of sizing:
When we think about sizing process, a question arises in our mind why sizing is done on the yarn? Here everybody should know one thing. The single ply yarn is not weavable without sizing. Now a question arises again in our mind why single ply yarn is not weavable without sizing? We clear the reason behind the necessary of sizing for single ply yarn. The warp ends in the warp sheet lye very close to each other. When the shedding motion is taken place during weaving, the ends rub to one another and rotate in clockwise or anticlockwise direction.
We also know that the the yarn twist is only the factor which helps to hold the fibres together in the yarn. Thus yarn twist helps to prevent the fibres in the yarn during weaving.
When the warp ends make up and down movement, the untwisting process of yarn takes place. This untwisting process causes fibres slippage during weaving.
When we apply a thin film of starch and binders on the yarn surface, the yarn twist gets permanent. Thus sizing process makes a single ply yarn weavable. The main objectives of sizing are given below:
1-To improve the weavability of the yarn.
2-To improve the strength of warp yarn.
3-To improve the degree of hairiness of warp yarn.
4-To optimise the abrasion resistance of yarn .
The parameters received from warping regarding the set
are given below:
Total ends = 14640 ends
Reed space = 126.20 inches
Warp count = 40s
Set( warp) length = 5000 metres
Sizing waste = 70 metres per set length
Actual warp length before sizing = 4930 metres
Sized warp length = 5020 metres
Warper's beam = 2200 mm
Number of beams = 20.
Now parameters required to size a beam are:
Beam width = ?
Denting order = ?
Beam width = Reed space (inches) + 20 mm
= 126.20 inches + 20 mm
= ( 126.20 X 25.4) + 20 mm
= ( 3205.48 + 20) mm
= 3225. 48 mm ( beam width)
This is very critical calculation in sizing. How to decide the denting order? When we group the warper’s beam s together, and we keep the zig- zag Reed in down ward position, and initiate the sizing process, the width of warp sheet is equal to the width of warper’sbeam. Now sizer brings the reed in upward position. The pointed dents of zigzag reed penetrate the warp sheet and the warp and automatically get passed through the dents of the reed. The ends density at both the selvedge and at remaining sheet vary due to difference of warper’s beams alignment.
Here sizer needs to correct the denting order at both the selvedge.
Now question arises, how to find correct denting order?
Approximate number of dents used = number of reed stripes X dents per reed stripes
= 25 X 60 dent
= 1500 dents
Denting order calculation sheet is given below:
Stretch % :
it is the ratio of difference between sized warp length and warp length before sizing to warp length before sizing expressed in the term of percentage.
Please note, the stretch% should be as minimum as possible.
WARP COVER IN SIZING:
The ratio of space occupied by yarn to total space occupied by warp sheet expressed in the term of percentage is called warp cover in sizing.
R f % or size concentration%:
The size liquor concentration is measured by refractometer, so that it is also call refractometer value in tem of % . The size liquor concentration is the ratio of solid contents to total volume of liquor after cooking expressed in term of percentage is called size liquor concentration% or RF % . The calculation of RF % of sizing liquor is given below: