Cotton Ply Twist Multipliers in Continuous Reactive Dyeing
Yarn ply twist multiplier controls intra-bundle pore radius; multipliers above 4.0 cause surface ring-dyeing frosting while values under 3.2 provoke migration.
S-on-Z Twist Balance
Yarn Construction
The relationship between the direction of the initial yarn twist and the direction of the plying twist determines the stability of the final thread. In an s-on-z twist balance, individual strands twisted in the S direction are combined using a Z direction twist. The resulting structure cancels out the internal rotational forces that would otherwise cause the yarn to kink or snarl.
Structural Stability
Achieving a perfect s-on-z twist balance ensures that the finished yarn remains dead, meaning it does not twist back on itself when held in a loop. Sewing threads rely on this configuration to pass through high-speed machines without tangling. Torque causes issues.
If the secondary twist is too high or too low, the yarn exhibits rotation, which can lead to spirality in knitted fabrics.
Mechanical Result
Plied yarns with this specific orientation offer improved abrasion resistance and a smoother surface. The s-on-z twist balance is a standard requirement for high-quality woven suitings and fine knitwear. Testing involves hanging a length of yarn and observing the number of rotations it makes as it relaxes.
Production Check
Technicians monitor the spindle speeds on the twisting frames to maintain the correct ratio between the two twist levels. Consistent results across different batches prevent stripes and shadows from appearing in the dyed fabric.