Mass Variation
Coefficient of variation of linear mass measured across short specimen lengths evaluates cross-sectional consistency along spun yarn strands. Quality control departments measure yarn mass cvm using capacitive testing instruments to grade grey yarn evenness in spinning mills. The metric expresses total mass fluctuation as a percentage of average yarn linear density.
Scope applies to continuous mass testing of spun staple yarns prior to warping and weaving.
Irregularity Index
Capacitive sensors measure capacitance changes as yarn passes through a narrow testing gap at high speeds, translating capacitance shifts into localized mass fluctuations. Natural flax fibres vary in length and fineness, making low mass variation harder to achieve in linen yarns than in combed cotton or synthetic filaments. High yarn mass cvm values indicate frequent thick places, thin places, and slubs, which cause fabric streakiness, uneven dye absorption, and frequent loom stops during weaving.
Chinese spinning mills utilize modern draw frames and online mass monitoring sensors to keep mass variation within acceptable customer limits. Spinning technicians analyze spectrograph charts generated during testing to diagnose drafting wave periodicities caused by worn top rollers or improper apron settings.
Quality Consistency
Yarns with low mass variation command premium prices in commercial markets due to superior weaving performance and uniform appearance in finished fabrics. Standard laboratory test reports list mass variation percentages alongside thin and thick place counts per thousand meters.
