Twist Variation and Its Effects
topic
Twist variation (CVtwist%) is measured by untwisting lengths of yarn and counting twists per metre, with coefficient of variation <5% acceptable for standard yarns. Between-spindle twist variation arises from spindle speed differences (belt wear, whorl diameter variation); within-bobbin variation from tension changes during cop build. Twist variation causes: fabric barre (visual banding from differential light reflection of high/low twist zones), uneven dyeing, and variable strength.
Role
Twist variation is a subtle but commercially significant quality defect because it is invisible in the yarn but becomes strikingly apparent after dyeing, especially in plain-weave or single-jersey fabrics where twist differences create regular banding patterns. Diagnosing twist variation and tracing it to its mechanical source (belt, whorl, ring rail) is an advanced process engineering skill that separates premium mills from commodity producers.