Learning Goal: Classify defects and apply AQL sampling for final random inspection.

Complete Lesson Content:

Defects are classified as Critical, Major, and Minor. Critical: affects safety (e.g., broken needle, sharp edges) – zero tolerance. Major: affects saleability or durability (e.g., hole, stain, measurement out of tolerance). Minor: slight deviation not affecting function (e.g., slight thread tail). AQL 2.5 for Major, 4.0 for Minor is common.

The final random inspection uses sample size codes based on lot size to determine how many pieces to inspect; accept/reject based on allowed defect numbers.

Definitions:

  • AQL Table – statistical table defining sample sizes and acceptance/rejection numbers.
  • Lot Size – total number of units in a shipment.

Step‑by‑step Explanation:

  1. Determine lot size (e.g., 1200 units).
  2. Refer to AQL table; for lot size 1200, sample code letter J, sample size 80.
  3. Inspect 80 pieces randomly.
  4. Count Major defects. AQL 2.5: accept if ≤ 5 defects, reject if ≥ 6.
  5. Count Minor defects. AQL 4.0: accept if ≤ 7, reject if ≥ 8.
  6. Critical defects: if any found, reject entire lot.

Best Practices: Combine with a measurement check on a separate sample. Always use the latest AQL standard and train inspectors.

Common Mistakes: Using the wrong AQL level for the product (e.g., too strict for basic t‑shirt, increasing cost).

Real Industry Example: A buyer specifies AQL 1.5 for Major defects on luxury garments, requiring tighter control.

Mini Case Study: A shipment of 5,000 dresses passed a final inspection at AQL 2.5, but the buyer found many minor snags. They increased the minor AQL to 2.5 in the next order.

Practical Activity: Given a lot size of 3,200 units, use an AQL table (provided) to determine sample size and accept/reject numbers for AQL 2.5 Major and AQL 4.0 Minor.

Assignment: Create a defect classification chart for a swimwear item, listing 3 critical, 5 major, and 5 minor defects, with clear descriptions.

Lesson Summary: AQL provides a statistical basis for accepting or rejecting a lot; use it consistently.

Key Takeaways:

  • Critical defects = zero tolerance.
  • Sample size depends on lot size.
  • AQL level reflects risk and quality requirement.
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