Quantifying Primary Trim Scrap in Rapier Weft Insertion
Primary rapier trim scrap depends on insertion geometry rather than fabric width, requiring exact tail length modeling to prevent yarn yield deficits.
Pre Winder Brake
Tension Control
Tension regulating devices are installed on modern looms to control the speed and drag of the weft yarn as it is pulled from the accumulator. The pre winder brake applies a controlled mechanical resistance to the yarn before it enters the storage coil. This device prevents yarn snarls and ensures a smooth, continuous feed to the insertion mechanism.
It is essential for managing the high-speed unwinding of flax yarns.
Mechanical Action
Unwinding linen yarn from a stationary package can generate erratic tension spikes that cause yarn breakage. The pre winder brake addresses this by using adjustable ceramic disks or leaf springs to apply a light, uniform drag on the yarn. As the weft accumulator gathers the yarn from the supply package, the brake stabilizes the ballooning effect and prevents the yarn from run-on when the accumulator stops.
Because flax is a natural fibre with variable thickness, the brake must be finely calibrated to handle slubs and thick-and-thin places without snagging. This precise control reduces warp-stop downtime and improves the overall efficiency of the weaving process.
Quality Impact
Inconsistent yarn feed tension leads to fabric defects such as tight picks or wavy surfaces. By ensuring a uniform yarn supply, the pre winder brake helps maintain consistent fabric width and density. It also reduces wear on the accumulator’s storage drum and the downstream insertion feeders.
This minor adjustment is a key factor in achieving high-speed, reliable linen production.