Yarn Appearance and Classimat Defect Classification

Yarn appearance and Classimat testing classifies objectionable defects (thick places, thin places, and foreign fibre contamination) by size and frequency using electronic yarn clearing instruments and appearance board winding to predict and control fabric visual quality. USTER Classimat 5 (or Quantum 4 yarn clearer on winding machines) classifies thick and thin places in a 23-class matrix: 12 thick place classes (A1–D4, length 1–32 cm × diameter deviation +45% to +400%) and 4 thin place classes (I1–I4, −30% to −60% diameter, 1–32 cm length) — defects in A, B, C, D classes represent different fault mechanisms and different fabric appearance impact. Appearance board testing (ASTM D2255, yarn wound in parallel on black velvet board, 120 wraps × 12 mm spacing, viewed at 600 mm distance under D65 illuminant at 1,000 lux): rated A–D (A = finest, most uniform, D = most uneven) — commercial warp yarn minimum Grade B3 for first quality woven shirting. Foreign fibre detection (Uster Tester 6 foreign fibre module, USTER Sentinel at winding, Premier iQ Air Elite 3): optical polychromatic sensor detecting coloured fibre intrusions (jute, PP, coloured cotton, human hair) — detection threshold 0.2 mm × 10 mm foreign fibre in white cotton yarn; false positive rate < 0.5 cuts per 100 km. Classimat cut rate optimisation (USTER ClassiMat 5 EXPERT software): balancing winding machine cut rate (breaks per 100 km) against residual objectionable defect rate — optimum cut setting at 80–120 cuts/100 km eliminates 95% of fabric-visible defects while maintaining winding efficiency >92%.