Diagnosing High CVm% — Evenness Faults
topic
High CVm% diagnosis follows: (1) Check spectrogram for periodic faults (chimneys = mechanical causes) vs high overall CVm without chimneys (drafting or material causes). (2) Periodic chimney at wavelength matching roller spacing: check roller eccentricity and apron condition. (3) High CVm without periodic fault: check roving CVm% (upstream cause), roller settings vs fibre length, and main draft zone settings. (4) Short-term variation: check top roller pressure and cot condition. (5) Between-spindle variation: compare individual spindle Uster tests.
Role
High CVm% is the most common yarn quality complaint and the starting point of most spinning quality investigations. A structured CVm% diagnostic protocol reduces fault-finding time from the typical 1–3 days of empirical trial-and-error to 4–8 hours of targeted investigation. Building this diagnostic capability across a quality team is the highest-return training investment available to a ring spinning mill.