Logic of Twist Contraction & Retraction factor of Textile Yarn

Twist contraction and retraction is very necessary to know for the best service on yarn spinning section. By contraction and retraction factor you will know when the textile yarn is followed a longer path for migration during twisting or how to maintain the draft setting properly.

Twist Contraction or Textile Yarn:

Normally before twisting, yarn  contains textile fibre individually in extended state. By twisting yarn is contracted and mass per unit length increases because when yarns are twisted, the fibres in the yarn have to follow a longer path for migration. For staple fibre yarn, this phenomenon is called contraction. For filament yarn this is called retraction.

Contraction Factor:

Contraction factor indicates the factor by which the draft must be adjusted to prevent the twist contraction from decreasing the size or count of staple spun yarn.
Contraction factor may be expressed as,
CY = Length of Zero Twist Yarn / Length of twisted yarn.

The contraction factor, which ranges from 1 for no contraction to infinity for contraction to zero length.

Retraction Factor of Yarn:

In represents the fractional decrease in length or increase in the linear density or twisting continuous filament yarns.
Retraction factor is expressed as,
RY = Length of zero twisted yarn length/ Length of zero twit yarn.

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