Cop Building and Winding
topic
Cop building is the process of layering yarn on the bobbin in a conical package by varying the ring rail traverse (up-and-down stroke) while the bobbin diameter grows. A correctly built cop has a stable conical base, cylindrical body, and tapered nose, with layers at 15–18° lay angle for good unwinding. Cop height is 150–200 mm; full cop weight 60–120 g. The ring rail lift and builder motion (cam-driven) determine layer angle and package density.
Role
Correct cop building ensures smooth unwinding in subsequent processes — winding, warping, and weaving. Poorly built cops (soft base, collapsed layers, pigtail nose) cause unwinding breaks on the autoconer, dramatically reducing winding efficiency and introducing yarn defects (splices) that degrade fabric appearance. Cop building quality is assessed by the Autoconer efficiency and splice frequency.