Warp and Weft Crimp Exchange Mechanisms during Wet Processing and Stentering
Warp and weft crimp exchange during wet finishing balances longitudinal overfeed and lateral rail draft to set fabric weight and arrest post-wash shrinkage.
Weft Bowing
Structural Distortion
Woven fabric widthwise distortions alter crosswise yarn alignment into an arc across the fabric plane. In finishing operations, weft bowing occurs when filling yarns curve away from a straight perpendicular line relative to the selvages. The defect governs fabric dimensional stability and garment panel cutting accuracy.
It does not include linear skewing where weft yarns remain straight but meet selvages at an angle.
Production Cause
Differential friction and speed variations across stenter frame rollers distort filling yarn alignment during drying or heat setting. Processing fabric through center-weighted liquid mangles forces the middle section of the filling yarn forward while selvages remain held by pin chains. In continuous finishing lines, weft bowing intensifies when fabric tension is unevenly distributed across the width of guide rolls.
The resulting displacement creates symmetrical or asymmetrical curves across the woven structure.
Correction Mechanism
Optical sensors detect yarn curvature and signal differential roll drivers to apply targeted corrective tension across the fabric width.
Quality Inspection
Fabric specifications define maximum allowable arc displacement relative to total fabric width. Presence of severe weft bowing causes seam twisting and uneven hanging in finished garments. Inspection tables measure maximum displacement from a perpendicular baseline using a straight edge laid across selvages.
Exceeding tolerance thresholds requires re-tentering and thermal re-setting to restore proper yarn geometry.