Fibre Migration
Residual tension within a sliver describes fell drift, an operational condition occurring inside the drafting zone of a linen spinning frame where unconstrained short flax fibres move laterally away from the main parallel axis. Natural variations in hackled line fibre length create pockets of low density inside the roving, allowing individual filaments to slip sideways under roller pressure before the twist takes hold. Mechanical draft ratios exceeding standard limits for wet spinning cause this lateral displacement, producing an uneven yarn diameter that fails the mill production standard for fine handkerchief yarns.
Export quality criteria established by the buyer reject any yarn lot displaying excessive mass deviation per linear metre, forcing mill operators to check top roller weighting whenever sliver irregularity exceeds tolerance.
Strand Irregularity
Roller pressure settings dictate whether individual filaments remain aligned or drift away from the central drafted band during drawing passes. Drafting cylinders turning at mismatched surface velocities exert uneven traction across the sliver, generating shearing forces that push loose tow fibres outward. Heavy drafting units operating at high rotational speeds accelerate this displacement, causing localized thinning in the spun thread.
Laboratory tests measure linear density variations using an electronic capacitance tester, recording mass fluctuations on the inspection certificate for every production shift.
Twist Deviation
Filament displacement reduces local tensile strength because fewer parallel fibres catch the inserted turns of twist during ring spinning. Low twist multipliers fail to bind the stray filaments into the yarn body, leaving loose hairs protruding along the finished line. Weaving sheds reject yarn with high hairiness indices because protruding fibres catch in the reed and cause warp breaks on the loom.
High drafting speeds increase sliver instability, making precise control over roller weighting mandatory for maintaining yarn integrity.
