Yarn Count Variation and CVcount%
topic
Count variation (CVcount%) measures the variability in linear density between bobbins, between frames, and between lots, determined by weighing standard lengths (120 yards for cotton, 90 m for metric). CVcount% should be <1.5% within a lot for standard yarns, <1.0% for premium yarns. Between-bobbin count variation causes fabric weight variation and weft banding (horizontal stripes) in woven fabrics. Causes include roving count variation, drafting irregularity, and humidity variation affecting fibre elongation.
Role
Count variation is the primary cause of fabric weight rejection — one of the most financially costly quality failures in yarn production. A lot with CVcount% of 3% produces fabric weight variation of 6–9 g/m², which routinely causes rejection of entire fabric orders. Systematic count monitoring with USTER or in-house weighing, and tracing causes back to roving, drafting, or conditioning, is a core quality management discipline.