Spinning Irregularity
Yarn thickness variations arising from uncontrolled fiber movement during drawing disrupt the uniformity of spun thread. This fluctuation, known as a draft wave, occurs when short fibers cluster together and move at the speed of the front rollers instead of the back rollers. In Chinese wet spinning mills, the resulting unevenness is recorded on the spectrograph chart of the yarn tester as a characteristic periodic mass variation.
Mechanical Source
Improper roller setting or insufficient pressure in the drafting zone causes the fibers to slip and form periodic thick and thin places. When the distance between the drafting rollers exceeds the average length of the flax fiber, the lack of control over fiber velocity leads directly to these waves. Wet spinning requires precise adjustments to the nip pressure and water temperature in the trough to limit the formation of such irregularities.
Maintaining tight tolerances in the mechanical drawing frame prevents the drafting defect from repeating across thousands of meters of yarn.
Fabric Defect
Loom efficiency drops when yarns with these periodic thin places are subjected to high warp tension. The thin spots break under tension, while the thick spots create unsightly slubs on the processed linen fabric surface. Fabric grading reports categorize these issues as warp defects, lowering the overall value of the finished cloth.
