Draft Waves

Wave Mechanism

Drafting zone dynamics depend on the gripping force of the rollers and the length distribution of the processed flax fibers. When the distance between the nip of the drafting rollers exceeds the average fiber length, draft waves form as fibers are pulled through in uncontrolled groups rather than a steady stream. This behavior creates a wave-like pattern of density that repeats at predictable intervals depending on the draft ratio.

Increasing the pressure on the rubber drafting aprons reduces this sliding action and establishes a more uniform flow of fibers.

Quality Effect

Woven fabric inspection identifies these periodic faults as bands or streaks that run across the finished cloth. The presence of draft waves compromises the yarn strength and leads to frequent breaks during high-speed weaving. Yarn testing instruments measure this irregularity to calculate the coefficient of variation in yarn mass.