AQL

Definition and Overview

AQL is a quality control concept used in sampling inspection, also called the acceptable quality level. Instead of checking every item in a lot, a sample is taken and inspected, and the lot is judged as acceptable or not by comparing it with a predetermined acceptance number.

AQL does not mean allowing defective products to be mixed in. It is a decision method for balancing inspection effort and quality risk, and it is used in combination with product specifications, inspection levels, and the severity of defects.

Role in Product Manufacturing

In apparel production, quality is managed at multiple stages, such as specification confirmation before mass production, in-process checks during sewing, and final inspection before shipment of finished goods. AQL is mainly used for sampling inspection when shipping or receiving completed product lots.

A final judgment based only on AQL cannot prevent defects that occur during the process. Confirming specifications with PP samples and identifying and correcting defect trends during sewing help reduce rework and delivery delays.

• Clearly state the inspection items, measurement points, appearance standards, and labeling details in the specification sheet.
• Classify defects as critical, major, or minor and set the judgment criteria.
• Share the lot range, sample size, inspection location, and person responsible for the judgment in advance.

Procedure and Practical Points

In practice, first determine the inspection quantity according to the lot size, and select samples without bias. Next, check appearance, sewing, measurements, attachment condition of accessories, stains, and labeling, and total the number of defects by category.

Compare the totals with the acceptance and rejection numbers to make a decision. If the lot is rejected, do not simply reinspect it; instead, investigate the process where the defects occurred, the location of occurrence, and any bias by color or size, and discuss responses such as sorting, repair, or remanufacturing.

• Before inspection, prepare a golden sample and a limit sample to reduce variation in judgment.
• Measure dimensions based on dimensional tolerances, and standardize the measurement method.
• For issues such as puckering and skipped stitches, it is effective to agree in advance on whether they are acceptable using photos or samples.
• Record not only the defect rate but also defect details and trends so they can be used for process improvement.

Quality Control and Precautions When Ordering

Between the ordering party and the sewing factory, specifying only the AQL value is not sufficient. It is necessary to agree in the purchase order or inspection criteria document on which defects fall into which category, the edition of the inspection standard, the definition of the lot, and how reinspection will be handled.

In particular, matters related to safety and legal labeling, foreign material contamination, needle detection failure, and major functional defects should not be treated the same as general appearance defects. Even if a lot passes AQL, there may be conditions that make it non-shippable on an individual basis.

Difference from Similar Terms

Sampling inspection is the inspection method itself, in which part of a lot is examined to judge the whole. AQL, on the other hand, refers to the quality level or judgment criteria used in that sampling inspection. In practice, the two terms are sometimes used with similar meanings.

Inspection is a broad term referring to the general task of checking the condition of products. It can be used for both full inspection and sampling inspection. AQL is a term related to the operation in which a lot is judged based on the sample size and number of defects as part of inspection.

Frequently Asked Questions