Twist Per Metre and Twist Multiplier
topic
Twist per metre (TPM) is the number of helical turns inserted per metre of yarn length. Twist multiplier (TM, also called twist factor, α) = TPM / √(count in tex) or TPM / √(Ne) depending on the count system. For cotton ring-spun yarns: TM ranges from 3.0–4.5 (weft) to 4.5–6.0 (warp). Higher TM produces stronger, harder, less extensible yarns; lower TM produces softer, weaker, more extensible yarns. Optimal TM for maximum strength is at the critical twist point.
Role
Twist multiplier selection is the primary engineering decision when setting up a ring frame for a new yarn count or end-use. It directly controls yarn tensile strength (by ±15–30% across the practical TM range), affects fabric handle, and determines suitability for warp or weft application. Incorrect TM is one of the most common causes of yarn rejection at the mill gate.