In a garment factory, checking every single piece in a large shipment is not always practical. AQL sampling provides a structured method for inspecting a selected number of garments and making a lot-level acceptance decision.
However, AQL is often misunderstood. It does not guarantee that an accepted shipment contains a fixed percentage of defective garments. It is a statistical sampling method used to make an inspection decision based on an agreed sampling plan.
What Is AQL in Garment Quality Inspection?
AQL stands for Acceptance Quality Limit. It is a parameter used in acceptance-sampling plans to determine how a production lot will be inspected and evaluated.
In apparel manufacturing, AQL inspection is commonly used during final inspection before shipment. Inspectors select garments randomly, check them against approved specifications and record the identified defects.
Three Important Inputs for AQL Inspection
1. Lot Size
Lot size means the total number of units presented for inspection. Before selecting a sampling plan, the factory and buyer should agree whether different styles, colours or production batches will be treated as separate inspection lots.
2. Inspection Level
ISO 2859-1 provides general and special inspection levels. The inspection level helps determine the sample-size code letter when combined with the lot-size range.
General Inspection Level II is frequently used in commercial garment inspections, but the buyer's written requirement should always be followed.
3. AQL and Defect Classification
Garment defects are commonly classified into three groups:
- Critical defects: Issues that may create safety, legal or serious compliance risks.
- Major defects: Defects that affect garment appearance, function or usability.
- Minor defects: Small deviations that do not significantly affect the garment's overall function or appearance.
Defect classification and acceptance criteria must be agreed with the buyer before inspection.
How AQL Inspection Works Step by Step
- Confirm the purchase order quantity.
- Define the inspection lot.
- Check the approved sample, measurement chart and technical specification.
- Select the applicable inspection level.
- Determine the sample size using the appropriate sampling table.
- Select garments randomly from different cartons.
- Inspect workmanship, measurement, appearance, labels and packing.
- Record major, minor and critical defects separately.
- Compare the results with the acceptance and rejection numbers.
- Prepare the final inspection report.
Practical AQL Inspection Example
Suppose a garment factory has completed an order of 2,400 polo shirts.
The buyer requests:
- Inspection method: Single sampling
- Inspection level: General Level II
- Major defect AQL: As agreed with buyer
- Minor defect AQL: As agreed with buyer
The inspector first identifies the applicable sample-size code letter using the lot-size and inspection-level table. The corresponding sampling-plan table then provides the sample size and acceptance/rejection numbers.
Important: Do not guess the sample size or acceptance number. Use the current applicable ISO sampling tables or the buyer-approved inspection system. The selected edition and inspection severity matter.
Difference Between Acceptance Number and Rejection Number
- Ac (Acceptance Number): The maximum number of defects or defective units permitted under the selected sampling plan for acceptance.
- Re (Rejection Number): The number at which the lot is rejected under that plan.
Always confirm whether the plan counts defective garments or individual nonconformities. These are not necessarily the same measurement.
Common Mistakes During Garment AQL Inspection
- Selecting samples only from easily accessible cartons.
- Using an outdated sampling chart.
- Mixing different styles without defining the inspection lot.
- Classifying the same defect differently between inspectors.
- Ignoring measurement and workmanship requirements.
- Assuming an accepted lot contains zero defects.
AQL Inspection vs In-Line Quality Control
AQL inspection is generally used to make a lot-level decision. In-line quality control is used to identify and correct problems while production is running.
A factory should not depend only on final inspection. First-output approval, sewing patrol inspection, measurement audits and defect analysis are important for preventing repeated quality problems.
Frequently Asked Questions
Does AQL 2.5 mean exactly 2.5% defective garments are allowed?
No. AQL is a parameter used to select an acceptance-sampling plan. It does not guarantee a fixed defect percentage in every accepted lot.
Can a shipment pass AQL and still contain defects?
Yes. Only a sample is inspected, so an accepted lot may still contain defects.
Is AQL inspection compulsory for every garment factory?
Requirements depend on buyer specifications, contractual arrangements and applicable standards.
Which standard is used for AQL sampling?
ISO 2859-1 provides sampling schemes indexed by AQL for lot-by-lot inspection by attributes. Verify the applicable edition before using its tables.
Conclusion
AQL sampling is an important part of garment quality assurance. However, its effectiveness depends on correct lot definition, random sample selection, consistent defect classification and proper documentation.
A strong garment factory should combine AQL inspection with continuous in-line quality monitoring to reduce defects and improve customer satisfaction.
0 Comments