The Acceptable Quality Limit (AQL) is a fundamental measure of standards used to conduct product inspections. In line with ISO 2859-1, it refers to the lower limits of acceptable standards for consumer products over the course of a number of inspections. At Global Inspection Managing, we use AQLs to determine whether or not a product order has met a client’s specifications.
AQL standards are helpful in that they can be used to find two very important figures. These include the number of units that need to be inspected in a given shipment and the number of defects that will produce a ‘fail’ result. The number of units that are inspected is called an ‘inspection sample’.
To determine the sample size needed for an individual shipment, organisations can use the AQL chart, which is made up of two tables.
The AQL chart can be used to determine how many defects are permissible during an inspection, as well as how many units should be inspected. If you are unfamiliar with the AQL chart, our inspectors will help you to select the AQL level that best fits your requirements.
The first table (shown below) can be used to select what is known as the ‘General Inspection Level’, of which there are three levels of requirement. Generally speaking, most companies select Level II, which is the standard for over 95% of inspections. The defect level must then be determined using the second table (also shown below), which uses a scale that ranges from 0 to 6.5. The acceptable defects limits are as follows:
- Critical defects: These defects are dangerous to consumers and, in line with current compliance regulations, should not exceed 0%.
- Major defects: These affect a product’s function or significantly affect its appearance. The limit is 2.5%
- Minor defects: These do not limit the use of a product but could still affect sales. The limit is 4%.
As already mentioned, Table 1 features three General Inspection Levels (I, II, and III) that determine how many units should make up a random sample.
As a general rule, companies should select Level II as standard. By selecting Level I, your inspector would examine fewer units. Although this may not be as costly in the short term, it may cost you more in the long term due to issues with quality.
A situation in which Level III needs to be used could include, for example, a new factory experiencing a series of failures related to quality control. This level will increase the sample size that the inspector will examine, making the results more accurate.
You may have noticed that the second column on Table 1 features four so-called ‘Special Inspection Levels’. Selecting one of these levels will lead to a smaller sample being examined.
Companies may wish to use these special levels for a variety of reasons including:
- Testing is too time-consuming or complicated
- Testing may damage the products
- There are few possible defects that represent a cause for concern
- The company is working to a strict time limit
You may be wondering why using AQL is preferable to testing every single product in a given batch. This is a reasonable question if you are only purchasing products in small volumes. As the quantities go up, however, such rigorous testing becomes less and less viable both in terms of time and cost.
AQL is a robust statistical model that has worked successfully for many decades. As such, it is virtually ubiquitous across the quality control industry.
Of course, it is important to remember that AQL inspections are not fool-proof and that some defects will go undetected. Indeed, AQL standards are not designed to guarantee defect-free purchases. In most cases, expecting shipments to be totally free of issues is unreasonable and not something that companies should aim for. Rather, AQL will allow you to select the percentage of defects that you are willing to accept.
To sum up, AQLs are a vital and intuitive tool used to help businesses tell inspection service providers how comprehensive they would like their quality control inspections to be.
If you are choosing a high level of quality control, remember that the factory you are working with will need to agree to your standards. It is also important to bear in mind that large-scale inspections are often costly, unnecessary and time-consuming.
If you are interested in using Global Inspection Managing’s services, take a look at our helpful AQL Calculator. It allows you to input your specific information in order to determine an AQL level that works for your company. For more information about AQL or any of our services, get in touch today.
What does Sampling Plan mean?
This is a Specific Plan that indicates the Sampling sizes to be drawn for Inspections and it is also associated with acceptance or non acceptance criteria in it.
What is AQL?
AQL means “Acceptable Quality Level”, it illustrates the acceptable quality level of products needed.The designed value of defects is expressed as a percentage by the particular sampling procedure.Different AQLs may be designed for different classifications such as Critical, Major and Minor defect.
What is the defect classification?
The defetcs are classified within 3 categories, "Minor", "Major" and "Critical".
A defect that is not likely to reduce the usability of the product, but is likely to reduce the salability or a discrepancy from the defined quality standard or not same as the original sample.Minor defects are usually small, in most cases the customer wouldn’t even notice a minor defect on a product.
A defect that is likely to result in product failure, reduction the usability of the product and obvious appearance defect affecting the salability of the product. A product with a major defect departs significantly from the buyer’s product specifications. Major defects are those which could adversely affect the function, performance or appearance of a product.
A defect that fails to meet mandatory regulations and / or affects the safety of the consumer when using the product.Critical defects render an item completely unusable and/or could cause harm to the user.These defects put businesses at serious risk of product liability issues and product recalls.