Quality Inspection and Defect Control
This domain tests the inspection checkpoints from fabric to final audit, the defect names an operator must recognise, and the basic cause-and-effect thinking used to stop repetition.
Standards and checkpoints
- Fabric inspection by the 4-point system: 1 to 4 penalty points per defect; a roll is commonly accepted at 20 points or fewer per 100 square yards.
- AQL sampling defaults often used in apparel: major 2.5, minor 4.0, critical 0 - always confirm against the buyer's manual.
- Checkpoints: first-piece approval, in-line or roving inspection, end-line 100% check, final AQL audit, metal detection.
Defect vocabulary
- Stitching: skip stitch, needle cut, broken stitch, uneven SPI, missing backtack.
- Seam: puckering, pleating, run-off, raw edge, seam slippage.
- Appearance: shade variation, oil stain, measurement out of tolerance, misaligned placket, wavy hem, twisted leg.
Cause analysis
- 5-Why drill-down and fishbone categories: man, machine, material, method, measurement, environment.
- Pareto ranking of defect types and DHU (defects per hundred units).
- Cluster analysis: if identical defects come from one machine or one operator, the cause is local, not material.
Worked example
Twelve skipped stitches appear in one bundle. Check the needle (bent, burred, wrong type), then the thread path, then hook timing; also check whether all twelve came from one machine or operator. Reasoning: the cluster points to a machine or handling cause rather than the fabric.
Traps
- Relying on end-line inspection alone, which makes rework far more expensive.
- Reading AQL 2.5 as "2.5% defective" - it is an acceptance sampling level, not a defect percentage.
- Passing a critical defect such as a needle fragment as minor.