Textile Production Processes and Quality Control
This domain tests the full production sequence and the standard inspection and test methods used to accept or reject fabric. Numerical defect-rating questions are common.
Process flow
Fibre, yarn spinning, fabric formation (weaving or knitting), wet processing (pre-treatment, dyeing, printing), finishing, cutting, sewing, final inspection and packing.
Inspection and acceptance
- 4-point system: score a defect 1 point up to 3 inches, 2 points for 3-6 inches, 3 points for 6-9 inches, and 4 points for over 9 inches. Maximum per defect is 4 points regardless of length.
- Points are normalised per 100 square yards; a common acceptance limit is 20 points per 100 sq yd.
- AQL 2.5 is widely used for major visual defects in garment inspection.
- Defects are graded critical, major or minor.
Tests to name
GSM, EPI/PPI, tensile strength, tear strength (Elmendorf), abrasion and pilling (Martindale), dimensional stability (home wash), colour fastness to washing, rubbing and light (ISO 105 series), pH of aqueous extract, formaldehyde content.
Worked example
A roll is 100 yards long and 60 inches wide. Inspection records 30 points. Does it pass at a 20 points per 100 sq yd limit? Area = 100 x (60/36) = 166.7 sq yd. Points per 100 sq yd = 30 x 100 / 166.7 = 18.0. 18 is below 20, so the roll passes on defect points. Reasoning: the denominator is the roll area in square yards, not the length in yards.
Traps that cost marks
- Scoring a 12-inch flaw as 3 points instead of 4.
- Dividing by roll length instead of area.
- Confusing AQL (acceptance sampling) with the 4-point system (defect rating).
- Testing unconditioned samples; standard atmosphere is 20 C, 65% RH.
- Listing a test without the standard or the acceptance level.