Acceptable Quality Level (AQL)

Understanding AQL

According to ISO 2859-1, the acceptable quality level (AQL) is used for goods and is defined as the "lowest tolerated quality level". The AQL informs you of the maximum number of faulty parts permitted or allowed during the random sample quality checks. The amount of faults to the total quantity is often stated as a percentage or ratio.

The Workings of Acceptable Quality Level (AQL)

When random samples of products are tested, the level of acceptable quality is considered to be met, especially if the number of faulty goods is less than a set quantity. Manufacturers will examine the different manufacturing process parameters to identify the regions producing the faults if the acceptable quality level (AQL) is not satisfied for a certain sampling of items.

Take a 1% AQL on a production run as an illustration. According to this ratio, about 1% or less of the batch cannot be faulty. There can only be ten flawed items in a production run of 1,000 items. The entire batch is discarded if 11 items are found to be flawed. In this scenario, it follows the Rejectable quality level (RQL) approach since there are 11 faulty items (more than the acceptable limit of 10).

For businesses aiming for Six Sigma level quality control-a quality-control approach created in 1986 by Motorola, Inc.-the AQL is a crucial metric. AQL is also known as the acceptable quality limit.

Differences in AQL Standards by Industry

A product's AQL might differ from industry to industry. For instance, because faulty items might pose health dangers, medical products are more likely to have stricter AQL.

A product having benign side effects from a potential flaw, such as a TV remote control, could have a less stringent AQL. Companies must compare the possible expense of a product recall with the additional costs involved with rigorous testing and likely more spoilage owing to a lower fault acceptance rate.

Naturally, customers would want flawless goods or services-the highest degree of acceptable quality. However, depending on considerations primarily connected to commercial, financial, and safety issues, sellers and consumers normally attempt to determine and define acceptable quality standards.

Using AQL Tables

AQL tables, sometimes referred to as AQL charts, are created to give consumers a standard for an acceptable level of manufacturing errors. They enable one to determine how many flaws would be acceptable for a business to reach a particular AQL. Tables are a component of ISO 2859.

As an illustration, suppose a business purchases 30,000 hats from a clothes manufacturer to be made in a single batch, and the buyer and the producer have agreed to an acceptable quality level (AQL) of 0.0 for critical flaws, 3.0 for major defects, and 5.0 for minor faults. By consulting the AQL tables, the buyer and producer may decide how many hats need to be examined to confirm that the specified AQL is being satisfied throughout production.

AQL Errors

Defects are instances where the quality standards set by the client are not met. There are three types of flaws in actuality:

• Critical flaws: Errors that, if left unfixed, might endanger people. Such flaws must be eliminated. A critical flaw is one with an AQL of 0%.
• Major flaws: Flaws that are often not tolerated by end users because they increase the likelihood of failure. Major faults usually have an AQL of 2.5%.
• Minor flaws: Errors that don't significantly impair a product's suitability for its intended use yet deviate from the required criteria; some customers may nevertheless choose to purchase such goods. Minor faults usually have a 4% AQL.

AQL in Actual Use

Acceptable Quality Level (AQL): Generally speaking, AQL refers to the lowest quality level that is nevertheless regarded as acceptable. It is the highest possible percentage of defects that may be deemed acceptable. There is a high probability of accepting the AQL lot. A 0.95 probability corresponds to a 0.05 risk.

Rejectable Quality Level (RQL): Also known as lot tolerance percent defective (LTPD), this approach typically denotes an inadequate quality level. Some tables have standardized the consumer's risk to be 0.1. Accepting an RQL lot has a low likelihood.

Indifference Quality Level (IQL): This quality level is between AQL and RQL. Each fault category is interpreted differently by various firms. But buyers and sellers settle on AQL criteria that are suitable for the amount of risk that each side takes. During a pre-shipment inspection, these criteria are utilized as a guide.

What criteria are used to assess if the AQL is being met?

The size of the lot or batch, the kind of inspection, the degree of inspection, and the desired AQL are required to compute AQL. Online AQL calculators are also accessible through various platforms. You would require a sample size of 500 units with a maximum of 21 flaws if your lot or batch size is 50,000, the inspection type is general, the inspection level is 2, and the proposed AQL level is 2.5. Anything more than that (i.e., 21 flaws/defects) will cross the line and lead to rejection.

What does a 2.5 AQL indicate?

An order must only contain 2.5% faulty items for it to meet the AQL of 2.5. The product does not adhere to the terms of the contract between the customer and manufacturer if more than 2.5% of the other is flawed. Therefore, only 1,250 of 20,000 pairs of shorts bought, for instance, might be faulty in order to achieve an AQL of 2.5.

What is the Standard AQL?

There isn't a set AQL. Depending on the product and sector, AQL varies. For instance, AQL must be extremely low in the medical sector since flaws in medical items or equipment might be dangerous to users. AQL may be greater in the apparel manufacturing industry. What the customer and manufacturer decide upon when placing the order, however, is ultimately what matters in deciding the AQL.

The Bottom Line

Generally speaking, AQL enables the vendor to produce quality goods quickly while still upholding the buyer's acceptable quality. It is typically utilized in large production orders and helps keep the customer and the supplier satisfied while delivering high-quality goods.