Viscoelastic Stress Relaxation Mechanisms in Sized Bast Fibre Warp Sheets
Viscoelastic tension relaxation in sized bast warps creates fell line migration and set marks unless controlled by active electronic let-off compensation.
Backrest Load Cell
Tension Measurement
Loom operation and tension control rely on real-time feedback from electronic transducers positioned on the yarn guiding assembly. The backrest load cell measures the continuous downward force exerted by the warp sheet as it passes over the backrest roller. This force is converted into a proportional electrical signal that represents the total warp tension during both the shedding and beat-up phases of the operation.
Signal Processing
Dynamic tension spikes must be filtered and processed to prevent the warp let-off motor from overreacting to short-term changes in yarn tension. An integrated backrest load cell transmits high-frequency output voltages to the central controller, which calculates the average warp tension over a set number of loom cycles. The processing unit then compares this average against the target tension defined in the product specification.
If the measured tension deviates from the setpoint, the loom controller adjusts the feed rate of the let-off motor to restore the correct tension. This prevents long-term drift in yarn tension that would otherwise cause variations in pick density or lead to excessive yarn breakages during processing.
Loom Regulation
Mechanical stability in the warp sheet is essential for maintaining uniform cloth properties across the entire length of the loom beam. When the backrest load cell detects a persistent tension deviation, it halts the loom if the let-off system cannot correct the error within specified safety limits. This automatic shutoff prevents the generation of defective fabric bands.
Dynamic Tension Control and Dobby Shedding Parameters for Flax Warps
Active tension control and asymmetrical dobby dwell minimize stress spikes on low-stretch flax warps to prevent end breaks and starting marks.