Winding Speed and Spin-Draw Processes
topic
Winding speed determines fibre structure: low-speed (500–1000 m/min): undrawn yarn (UDY), amorphous, birefringence <0.01; medium (1500–3000 m/min): partially oriented yarn (POY), birefringence 0.04–0.07; high (3000–4500 m/min): fully oriented yarn (FOY), birefringence >0.1; spin-draw (direct): high-speed + inline draw produces fully drawn yarn (FDY). Spinline stress determines orientation level.
Role
Winding speed is the primary variable controlling the balance between molecular orientation and crystallinity in as-spun polyester, which determines all subsequent drawing requirements and final fibre mechanical properties.