AQL Defect Classification: How to Classify Defects

by | Nov 12, 2019 | AQL, Product Inspections, Quality Control

​How does your QC inspector determine whether your products are acceptable or not during a third-party inspection?

Imagine you’re manufacturing a standing desk at a factory in Vietnam.

You hire a service provider to conduct a final random inspection and the inspector travels to your factory. During the inspection, they pick a piece and measure the surface of the desk, noting that it measures 26.1” x 22”.

According to your product specifications, the surface of the desk is supposed to measure 26” x 22”, which means there is a variance of 0.1 inches.

With that in mind, is the item acceptable?

The answer is… It depends. More specifically, it depends on your own standards and how you have classified defects.

Product inspections are generally conducted based on AQL sampling which helps determine how many pieces to inspect and how many defects will trigger a failed inspection.

There are three types of defects—minor, major, and critical.

How you classify that 0.1-inch variance can mean the difference between a passed inspection and a failed inspection.

In this article, we talk about how defects are classified and how you can ensure that your AQL defect classification matches your true quality standards.

The 3 Types of AQL Defects You Need to Understand

To conduct an inspection based on the AQL standard, you need to put all potential defects that could occur with your product into three categories.

#1 Minor Defects

A minor defect is one where the item deviates slightly from your specifications. A defect is only minor if you believe it is saleable and would not trigger a return.

For example, imagine your product is a 24-inch computer monitor and the unit inspected has a quarter-inch scratch on the back.

Clothing label with strange writing and poor grammar

Read this label carefully… Major or minor defect?

That small scratch might not be very noticeable and won’t affect a consumer’s experience of actually using the monitor, so it could be considered a minor defect. But if it were on the face of the monitor, that would be a different story.

Another example of a minor defect would be a slight color variance, i.e. a blue stapler from your production run that is in a slightly different shade than was specified.

It is really only noticeable when you compare it side-by-side with your golden sample, so it could be classified as a minor defect.

Any time you specify measurements, you also need to set a specific tolerance, i.e. anything within +/- 2% variance is a minor defect.

In this case, since the standing desk we discussed earlier had a 0.1-inch variance, it would be classified as a minor defect.

However, a 0.6-inch variance would be outside of your tolerance range and thus a major defect.

#2 Major Defects

A major defect is one that makes your product unsaleable or likely to be returned by a consumer—such as a monitor with a scratch on the front.

Some other examples of potential major defects would be a lock with a key that doesn’t open it, a blue cup inside a package that says it’s red, or a pair of skinny jeans that are labeled as relaxed fit.

These defects are very noticeable and you could expect the items to be returned.

So, what is a critical defect?

#3 Critical Defects

A critical defect is one that could cause injury to the consumer or even death.

Dress shirt with sleeves half as long as they should be

Look at these sleeves… Fashion trend or major defect?

For example, imagine a wooden picture frame that is splintered, a phone with a battery that overheats during battery cycle tests, or a piece of furniture that topples during an incline test.

These would all likely be considered critical defects and would result in an immediate failed inspection.

Also, any item that has insects, blood, or hair inside the packaging is considered to have a critical defect.

Now that we’ve talked about the three types of defects, let’s discuss why it is important for you to put serious thought into developing a defect list.

Why You Need to Develop Defect List

As we’ve stated already, an inspected product can have minor, major, or critical defects.

Sure, your third-party quality control company might have default suggestions for how to classify certain defects. But ultimately the responsibility falls on your shoulders since you understand your product and target market better than anyone else.

A high-end retailer is going to have different quality expectations from a low-end bargain brand.

That’s why, as the buyer, you need to work collaboratively with the QC company to create a list of defects and tolerances that are specific to your situation.

As you work with the service provider to develop a quality control checklist, you should put effort into brainstorming and coming up with every potential defect you can think of and what kind of major and minor defects to look for.

How do you do this?

How to Develop a Defect List

For items that have been sold before, you can look at information like return data and customer emails or complaints to help you come up with a list of common defects.

Christmas decoration that says

Would you consider this “Leb it Snow” decoration saleable?

If you haven’t sold the product before, you can think about similar products you have sold and pull up any data you have for those.

But you can also just think about your product. What is it supposed to look like? How is it supposed to function?

Take a look at your samples. What issues or potential issues do you see? Compare your samples to their ideal specifications. What deviations do you note?

Test your samples rigorously to see what issues develop. You can expect that similar issues might be found with products from mass manufacturing.

Once you have your inspection checklist in place and your defects are well defined, you should always include it with your purchase orders.

As more and more people buy the product, you can revise your defect list over time based on their feedback.

It is important to remember that the development of a QC checklist and your defect list is a collaborative process.

See what ideas your QC company has, add your own, and set appropriate tolerances.

Summary: Understand the Defect Types and Create Your List

It is important to remember that there are three types of defects for use with AQL sampling plans—minor, major, and critical.

Keep in mind that misclassifying a defect can mean the difference between an inspection passing and failing.

Put serious thought into your defect list and set specific requirements and tolerances for your QC checklist.

Work collaboratively with your inspection services provider to create a list that matches your needs.

Doing so will help you ensure product quality.

For more information about AQL, including what it is, how it works, and the difference between the general and special inspection levels, we recommend you download the following white paper.

Free White Paper: AQL Inspections 101

As a consumer goods importer, the quality of your products is key to your success. Good quality products will earn you favorable reviews and repeat purchases.

AQL determines the sample size for your inspections and understanding it is important.

This white paper will teach you all the basics of the AQL method.

Note: This article was originally published in January of 2018 and was updated in November of 2019.

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