Quantifying Wet Spinning Limits for Low Cohesion Bast Fiber Slivers
Low cohesion flax slivers collapse under high draft ratios, requiring reduced trough temperatures, higher roving twist, and tight ratch settings to hold count.
Faller Bar Pinning
Needle Arrangement
Distribution and density of steel pins across the drafting bars in a drawing frame determine the precision of the combing and aligning process for flax slivers. This specific configuration, referred to as faller bar pinning, dictates the spacing and height of the needles that penetrate the fibre bed. Fine counts of yarn require a high pin density to prevent uncontrolled fibre clusters from passing through the drafting zone.
The pinning density is measured in pins per inch or pins per centimeter.
Fiber Control
Drafting action relies on the pins to grip the flax fibres and prevent them from moving faster than the draw rollers. Adjusting the faller bar pinning to match the average staple length of the flax lot prevents drafting waves and reduces yarn irregularity. During the drafting cycle, the pins must penetrate the sliver completely and withdraw cleanly without causing fiber damage or splitting.
Fiber breakage is minimized by using tapered pins. Coarser fibers require open pinning to avoid choking the drawing zone and causing mechanical jams.
Mechanical Wear
Maintenance of the drafting field requires regular inspection of the needles for bending or loss of sharpness. Damaged faller bar pinning causes uneven drawing and increases the frequency of thin places in the spun yarn. Mills replace the worn pin strips on a scheduled rotation to ensure uniform yarn quality.