Winding Tension and Cop Hardness
topic
Winding tension (yarn tension at the bobbin surface during wind-on) determines cop hardness, which affects: unwinding behaviour at the autoconer, yarn elongation recovery (overstretched yarn has reduced fabric elongation), and dye uptake (tightly wound layers absorb less dye). Winding tension = traveller weight × (spindle speed / traveller speed)² × balloon factor. Tension increases from bobbin base (large diameter) to nose (small diameter) during build, causing hardness variation.
Role
Winding tension management prevents both cop collapsing (too low tension) and yarn damage (too high tension), which are expensive quality failures. Over-tensioned inner layers of compact cops can have permanent elongation set, causing the fabric from inner-layer yarn to have different dimensional stability after washing — a subtle defect that causes consumer complaints in premium shirting and hosiery.