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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Yarn count variation:

The yarn count plays a very important role in fabric quality. Any unevenness in yarn appear in the form of fabric defect on the fabric surface. Many times yarn count variation results as a big issue in respect of fabric defect. There may be two kinds of defects due to yarn count variation in the fabric.

Warp count variation:     Any kind of variation in the count of warp yarn results in the form of continuous thick end or thin end which is visible on the fabric. If warping if the beam has been done on sectional Warping machine, the thick or thin end appear in each section. If warping has been done on direct Warping machine, the thick or thin end appear at particular place in group. This kind of defect appear s only when one or more cones contain count variation in whole yarn length. This kind of uneven appearance of the fabric cause rejection of the fabric. The mending of this type of defect depends upon the type and length of the defected fabric. If the length is short say 2-3 meters and one or two thick or thin ends are appearing in the fabric, then mender can change this end with the same count of yarn. If the length is too high or there are many thick or thin end in the fabric, then the fabric gets rejected because the replacement of defective thread with the fresh thread is a much time-consuming process. If mending cost is more than fabric cost, then it is better to reject the defective fabric.

Weft count variation:

The weft count variation is a more serious issue than warp count variation. In the most time fabric gets rejected due to weft count variation. The weft yarn count variation affects the fabric surface in many forms. 
If the weft yarn count varies for a short length say 4 - 5 metres, the weft bars appear on the fabric surface. It can be repaired by replacing the defected pick by fresh yarn. 
If the weft count varies for a long length, it results in form of low and high thickness bands in the fabric. If there is very low count variation for long length, the bands do not appear clearly in the grey fabric. When this fabric is dyed , the light and dark colour bands appear prominently on the fabric surface.
If the weft yarn count variation occurs for long weft yarn length, the GSM of the fabric also varies. 
Individual weft bar can be repaired but GSM variation, thick and thin bands are not repairable. These irregularities are unacceptable. The whole fabric gets rejected due to these kinds of defects.

                                 THE END