Quality Control, Inspection and Defect Identification
Expect questions on the four-point fabric system, AQL sampling, defect classification by severity, inspection stages, and root-cause thinking.
Inspection stages
First-piece approval before bulk running; in-line or roving inspection to catch faults early; end-line inspection of every garment or by AQL; final audit; metal and needle detection with a needle-control policy.
Four-point system (fabric)
Defect up to 3 inches = 1 point; over 3 up to 6 = 2; over 6 up to 9 = 3; over 9 = 4. A maximum of 4 points per linear yard. A hole is counted once, not on both faces. Results are usually expressed as points per 100 square yards; many buyers accept up to about 20.
AQL and defect classes
AQL is a sampling standard, not a zero-defect promise: a lot can pass with some defects present. Defects are classed as critical (safety or needle risk), major (open seam, wrong shade, measurement outside tolerance) and minor (loose thread, slight oil mark). Typical buyer levels are AQL 2.5 for major and 4.0 for minor.
Common defects and causes
Skipped stitch, open seam, raw edge, puckering, needle mark, oil stain, wrong shade, measurement out of tolerance, twisted leg, mismatched placket. Trace with 4M: man, machine, method, material.
Worked example
A roll 100 yards long and 60 inches wide carries defects: two 1-inch holes (1 point each = 2), one 7-inch stain (3 points), one 10-inch tear (4 points). Total 9 points. Points per 100 square yards = 9 x 3600 / (60 x 100) = 5.4, well under 20, so the roll is acceptable on the four-point scale. Reasoning: each defect is scored once at its longest dimension, summed, then normalised to area.
Traps that cost marks
Double-counting a hole on both faces, treating AQL as a zero-defect standard, and passing a measurement that is outside tolerance because the seam looks neat.