Studies on Noncontact Heater for Textured Yarns

Part 3 : Yarn Tension in False Twist Texturing Process

Abstract

In false twist texturing processes, the yarn tension is very important factor affecting manufacturing process and characteristics of textured yarns. When a running yarn is twisted initially by a spinner, the yarn tension in the twisting zone is increased very rapidly to the maximum point-and then gradually decreased to the specified equilibrium level. This phenomenon is expressed by the following equation :
σL (t) = [1/ (1+kε₁) α {(1-e^-υ₂t/L) +e^-υ₂t/L·cosωLt} -1] ·E·cosωLt
where, σL : yarn tension in the zone L
E : elastic modulus of yarn
V₁ : surface velocity of 1st feed roller
V₂ : surface velocity of 2nd feed roller
α : V₁/V₂=feed ratio
L : distance between 1st roller and spinner
t : time elasped after the beginning of twisting ωL : twist angular velocity of running yarn in the zone L
k=ε₁"/ε₁
ε₁ : longitudinal strain due to the pre-tension
ε₁" : sectional strain due to the pre-tension
An investigation has been made of the yarn tension affected by the twist, heater temperature, feed ratio and the properties of untextured yarns. The equilibrium tension of running yarn decreases with increasing the twist and the heater temperature .
The coefficient of friction between the spinner and the processed yarn decreases with increasing the feed ratio and number of twists.