Yarn Defect
Structural defect in core-spun yarn describes the displacement of the internal elastic filament relative to the surrounding staple fiber sheath. During downstream processing, core slippage can lead to irregular fabric appearance, uneven dyeing, and puckered seams. The fault occurs when the frictional hold between the sheath fibers and the core filament is insufficient to withstand mechanical tension.
In many cases, it creates bare spots of elastane that break during knitting or weaving.
Friction Mechanism
Drafting zone adjustments during yarn spinning establish the required coherence between the two yarn components. Slippage is more frequent when the elastane draft is too low or when the staple fibers are too smooth to grip the core. This mechanical failure occurs under the high tensions of warp preparation and weaving.
Inspection Procedure
Quality control departments use tensile testers and magnifying systems to spot core slippage before yarn reaches the loom. Technicians stretch yarn samples to their limits to see if the core retracts inside the sheath. This test ensures that only stable yarn enters the manufacturing stream.
Prevention Method
Improving the roving twist or adding a surface finish to the staple fibers can significantly increase yarn cohesion. Spinners adjust the guide positions in the spinning frame to ensure the core is centered. This adjustment distributes the clamping force evenly and avoids slippage.
