Attenuating Mechanism
Progressive longitudinal attenuation of carded or combed flax slivers through sets of differential-speed drafting rollers reduces strand weight per unit length. Mechanical execution during sliver drafting aligns individual flax fibers parallel to the strand axis while blending multiple slivers to improve weight uniformity. Draw frame operations convert heavy, irregular fiber strands into thin, homogeneous slivers suitable for roving or direct spinning.
This mechanical attenuation process governs fiber parallelization and linear mass reduction in preparation frames and does not impart final yarn insertion twist.
Kinematic Control
Differential surface speeds between back drafting rollers and front drafting rollers force flax fibers to slide past one another, thinning the fiber assembly. Multi-zone drafting systems use faller bars or pin gill beds to control short flax fibers and prevent uncontrolled floating fiber movement between roller nips. The draft ratio equals the surface speed of the front delivery roller divided by the surface speed of the back feed roller.
Incorrect draft settings generate periodic mass variations known as draft waves, causing thick and thin places in downstream yarn.
Linear Uniformity
Continuous monitoring of draft ratios and delivery sliver weight prevents yarn linear density defects in subsequent spinning operations. Proper execution of sliver drafting ensures smooth roving formation and reduces end breakage rates on wet spinning frames. Quality control records track mass variation CV percentages across all draw frame deliveries.
