Quality Control, Inspection and Defect Analysis
Scope
Quality standards, inspection stages, AQL sampling, the 4-point fabric system and defect analysis.
Core rules
- Inspection: incoming fabric, in-process, final and pre-shipment.
- 4-point system: 1 point for defects up to 3 in, 2 for 3-6 in, 3 for 6-9 in, 4 for over 9 in; scored per 100 sq yd.
- AQL sampling to ISO 2859; classify critical, major and minor defects.
- Defects: slub, hole, oil spot, shade variation, bowing, skipped stitch, puckering.
- Metrics: DHU (defects per hundred units), first-pass yield, rework rate.
- Corrective action: contain, root-cause with 5 Why or fishbone, correct, verify.
Worked example
A 100 sq yd roll has 12 points. Reasoning: the score is 12 points per 100 sq yd; if the buyer's limit is 20 points per 100 sq yd, the roll passes. If the roll were 50 sq yd, points would normalise to 24 per 100 sq yd and it would fail.
Traps
Reporting points per roll rather than per 100 sq yd; treating all defects as equal; ignoring shade band across the lay; sampling only the top ply.