Acceptable Quality Limit (AQL) is a statistical method widely used to determine the maximum defect tolerance of a production batch and the sample size checked shall be randomly drawn from the production batch.
The below Acceptable Quality Limit (AQL) is made according to ISO 2859 Part 1 for normal inspection.
Step 1: Insert the lot or batch size of the products we want to inspect
Step 2: Choose the inspection level.
Best Practice: Normally General Inspection Levels II is applied for visual check and Special Inspection Level S2 is applied for special test and dimension check.
Step 3: Choose the AQL Level for critical, major and minor defects.
Best Practice: In industrial consensus, critical defect is usually set to “not allowed” which means zero tolerance.
For electrical and high value product, major defect is usually set at 1.5 and minor defects is set at 4.0
For hardgoods and softgoods, , major defect is usually set at 2.5 and minor defects is set at 4.0
Critical Defects | Major Defects | Minor Defects | |
Criteria of Definition | · Violation of regulatory requirement · Pose a safety risk to consumer · Potential to cause product recalls and brand damage | · Affects the normal function of product · Potential to affect salability or cause consumers’ complaint · Deviation from product specification | · Barely noticeable visual defects (normally at arm distance) · Not affecting the normal function · Not desirable to be found in large quantities · Can be removed by reworking |
Examples | · Broken needle · Insects · Mold · Rusty · Sharp edge · Small parts | · Obvious scratch on cosmetic · Obvious color difference · Out of tolerance dimensions · Different critical components | · Hidden mark · Removable dust · Untrimmed threads |
AQL tables also known as AQL charts have two tables. Table 1 is used to determine the sample size for inspection. Table 2 is used to define the number of allowable defects.
Table 1: Sampling Size Code Letters
We find the code letter correspond to the lot size.
Table 2: AQL for single sampling plan for normal inspection
In the table 2, we find the sample size according to the sample size code in table 1. The maximum allowable limit is defined in table 2 based on the AQL level we choose for major and minor defects. Acceptance number is the maximum number of defect piece accepted.
AQL (Acceptable Quality Level) charts are a cornerstone in quality control, primarily because it streamlines the inspection process, making it both cost-effective and time efficient. By setting clear thresholds for acceptance, AQL table facilitate decisive action, reducing the likelihood of indecision that can lead to delays and increased costs. The widespread acceptance by factories underscores the reliability. Moreover, AQL charts ensure consistency across production batches, which is crucial for maintaining quality standards over time. This consistency also supports the implementation of switching rules, which provide the flexibility needed to adjust inspection rigor based on the quality history of the products, thereby optimizing the balance between quality assurance and operational efficiency. In essence, AQL charts are a versatile tool that enhances the quality control process by bridging precision with practicality.
KOL Quality utilizes the AQL (Acceptable Quality Level) table as a statistical tool to guide our quality control inspections, ensuring that the products meet the industrial standards required for consumer safety and satisfaction. The AQL table helps determine the sample size needed for inspection based on the lot size of the products, and it sets the maximum number of acceptable defects. By adhering to the AQL standards, buyers can make informed decisions about whether to accept or reject a product lot. This systematic approach allows KOL Quality to maintain high standards while also being efficient and consistent in our inspection processes.
