A Quick Guide to Understand AQL for Inspections

Whether the product is manufactured in batches or not, it is always necessary to ensure that the manufacturers meet the essential standards. Manufacturing companies typically produce batches of goods. Trying to go through all of the products one by one would be very time-consuming and exhausting. Sometimes it is not even possible. In light of this, the AQL was introduced.

What is AQL?

AQL is also known as “Acceptable Quality Limit.” It is generally defined as the number of faults per sample acceptable for the batch. A batch is rejected if it has more faults than the acceptable quality level.

“The acceptable quality limit (AQL) is the worst tolerable process average (mean) in percentage or ratio that is still considered acceptable; that is, it is at an acceptable quality level,” according to Wikipedia.

What is the importance of acceptable quality limits?

AQL standards provide valuable information to your inspection teams and you:

• How many units should be inspected in an individual shipment, and
• how many defects will trigger a failure?

The number of units you inspect is known as an “inspection sample.”

You can determine these parameters using the AQL tables. You can see a sample AQL chart below:

 

In testing and inspection, an acceptable quality level serves as a standard that describes the acceptable range of defects of components during a random sample during the inspection. A physical (mechanical) inspection or an electronic or electrical test may identify defects of three levels: critical, major, and minor.

• Critical defects: defects that breach mandatory regulations and compromise the safety of consumers/end users.
• Major defects: defects that severely reduce the usability or saleability of the product.
• Minor defects: defects that fall short of quality standards but do not significantly affect a product’s usability or saleability.

Knowing the Difference Between General and Special Sampling

There are two types of sampling levels in the AQL: General sampling and Special sampling. As its name suggests, the latter is used in a variety of special cases, such as damage assessment.

Under the General Sampling Level, there are three sub-levels, namely GI, GII, and GIII, which represent ‘Reduced’, ‘Normal’, and ‘Tightened’ sampling. As you advance from GI to GIII level, the sampling size to lot size ratio rises. Mass consumer products are typically inspected using GI and GII.

What if your product fails to meet AQL?

An inferior quality product might result in a failed inspection, so if your supplier finds that your order is disappointing, you can ask them to hold the shipment. Quality issues can typically be dealt with in several ways, including:

• If the rework is realistic and unlikely to cause further problems, ask your supplier to fix the affected units,
• Having your supplier replace the damaged units,
• Returning unsellable goods, or
• destroying any unsellable units so that suppliers cannot sell them to competitors or the black market.

Related Articles: Inspection Management and Quality : Understanding the Core Metrics

In the case of a failed inspection, your approach will largely be influenced by

1. the strength of your relationship with your manufacturer/supplier,
2. the severity of the defect,
3. the value of your order, and
4. the urgency of your shipment.

Understanding the Terms Acceptance and Rejection Point in AQL

ACCEPTANCE POINT

Acceptance points typically appear in the AQL table as “Ac” and indicate the maximum number of defects that can be accepted within a given sample size. The acceptance point of each defect class varies since many importers assign different AQLs to them. Generally, importers define AQL values for minor and major defects as higher than those for critical defects, indicating their preference for this range. 

An AQL is considered passed if the sample finds the same number of defects or fewer than your acceptance points for the class of defects.

REJECTION POINT

In the AQL table, the rejection point, commonly referred to as Re, indicates the minimum number of defects required to reject an order based on given sample size and AQL. The acceptance point and the rejection point are closely related. In a single sampling plan, you will always find your rejection point one value higher than your acceptance point.

When a sample has more defects than the tolerance level, it cannot be considered compliant. When an importer detects the presence of enough defects, they will typically reject the order or ask their supplier to hold it until the defects are fixed.

Therefore, the sample size will affect how transparent and accurate your results are, just like all sampling plans. Whenever you make shipping decisions based on the results of acceptance sampling, there is the risk of rejecting “good” lots or accepting “bad” lots.

On the other hand, AQL ensures that you do not inspect more goods than required, saving time and money by avoiding unnecessary inspections. A sample check is by far the most cost-effective way for importers to confirm their goods are as described before shipment.

How Does AQL Make a Better Choice Than A 100% Inspection?

Customer questions like this are common. Some of you may think, “If I had a 100% inspection, my products would be safe.”

This is acceptable if you are purchasing small quantities. Nevertheless, as you increase your order quantities, it becomes less viable. Inspecting a facility takes significantly more time and costs more money.

AQL is a statistical model that has been successful for years. For this reason, it has become an industry standard.

Although AQL inspections will prevent defects, they will not guarantee a defect-free inspection. It is not intended to do that.

Managing AQL Using a Powerful Inspection Management Software

With a traditional approach to AQL and inspections, you may run into risks of delivering average quality goods to your customers. It may impact your brand reputation in the long term. Instead, you should automate the entire process of inspections – from specifying AQL to defining sample size for consistent quality products and services.

It can be challenging to find the right inspection management software, but here is a quick recommendation to your escape from the research and selection efforts. You can count on Qualityze Inspection Management Software.

Using Qualityze Inspection Management, you can set up a schedule for stringent inspections based on severity. Using customizable workflows and forms makes customizing sampling plans easier to comply with regulatory requirements. With this solution, you can specify AQL/LTPD, the Acceptable Quality Level, and the Lot Tolerance Percent Defective to efficiently perform stringent inspections.

Establishing a severe-based sampling plan assures the incoming materials comply with quality requirements and compliance requirements.

With Qualityze Inspection Management, you can use standardize processes to: Setup Sampling Plans, Inspection standards, Inspection Types and Purchase Orders, Perform Inspections, Verify Samples’ Variables and Attributes, Use Severity based sampling plan for more stringent inspection, Generate a NC for samples that failed inspection criteria, Evaluate Material Reinspection requirements, and Integrate with ERP systems for Purchase Order information.

Related Articles: Inspection in Manufacturing Processes: Why It is Important

Key Takeaways

Samples taken from AQLs are an essential part of most quality control inspections. You know what they look like and how to use them to decide whether or not to accept an order of goods. The software can make your job simplified. You can define various AQL’s for the variety of goods you deliver. Generate important reports and analyze the collected information to make informed decisions and consistently provide quality products and services.

Keep in mind that superior product/service quality plays a significant role in gaining a bigger market share.

If you want to know more, please contact our customer success team directly at +1-877-207-8616 or email us at info@qualityze.com, and we will be right there for you.