Count Variation Between Bobbins
topic
Between-bobbin count variation diagnosis: (1) Test 20 bobbins for count; calculate CVcount%. (2) If CVcount% >2%: trace to upstream — weigh finisher draw frame sliver; if sliver CVcount% >0.8%, problem is upstream. (3) If sliver count is uniform: check ring frame draft (gear changes, broken draft gears), ring rail traverse (affects winding density), and creel roving tension (uneven tension changes effective draft). (4) Seasonal CVcount% increase: check humidity and conditioning of roving before spinning.
Role
Between-bobbin count variation investigation is the quality investigation most frequently required by woven fabric customers, because fabric weight variation (directly caused by weft count variation) is tested on every fabric lot. The ability to rapidly diagnose whether count variation is upstream (draw frame) or at the ring frame level, and to identify the specific cause, is a skill that resolves customer complaints 2–3× faster than undirected investigation.