Friday, June 7, 2019

FABRIC DEFECTS DUE TO YARN TWIST VARIATION, A GREY FABRIC DEFECT


GREY FABRIC DEFECTS DUE TO YARN TWIST VARIATION:

The main fabric defects appearing in the fabric due to the yarn faults are given below:

Yarn twist variation:

The yarn twist variation is a very serious yarn defect. It is directly reflected in fabric quality as well as productivity. If the yarn has low twist portion in the yarn, the tensile strength of the yarn decreases. The decreased tensile strength of yarn influences the warp breakage rate of loom. Heavy warp breakage rate results poor fabric quality in terms of broken end , missing end, and short end. When the degree of yarn twist( turns/inch) varies ,the yarn diameter also gets changed. If the degree if twist is decreased, the yarn diameter is increased. And if the degree of yarn twist increased, the yarn diameter is reduced.
 The yarn twist variation reflects on the fabric surface in the form of four pattern.

Warp bars due to yarn twist variation:

If the twist variation comes in individual warp end, it appears in the form of warp bar. It does not appear clearly in the grey fabric. It is very difficult to identify this kind of fabric defect in grey fabric. When the fabric goes under processing, it gets clearly visible on the fabric surface. The twist of the yarn directly affects the amount of light to be reflected by fabric surface. The warp end having different degree of twist reflect low or high amount of light in comparison of other ends. 

Weft bars due to yarn twist variation:

If the degree of twist varies in the weft yarn, for very short length, it results in the form of weft bar on the fabric surface. It behaves like warp bar.

  Warp bands due to yarn twist variation:

Warp band due to twist variation appear if one or more bags of warp yarn having different degree of twist get placed on the warping creel at one position. This warp band appears clearly on the fabric surface after dyeing. Normally this kind of direct comes rarely due to mixes yarn supply by tarn manufacturer.

Weft bands due to yarn twist variation:

If the weft yarn has long continuous portion having different degree of twist, it appears in the form of weft band due to yarn twist variation. It gets much prominent after processing.


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