Quality Knowledge

Classification of Defects in Quality Control Explained

classification of defects in quality control

It’s not enough for a quality control inspector to merely identify faulty items in your production line. They must also categorize and report any defects they have found according to your pre-set requirements. This process is known as classification of defects in quality control, and it is crucial.

Knowing what types of defects you are dealing with allows you to make informed decisions about every product batch. Depending on the severity and number of the defects, you may accept the items or return them to be reworked. Alternatively, you could destroy the products and ask the manufacturer to produce replacements.

In any case, if you do not address product defects adequately, you risk losing customers, money, and even your whole business.

Classification of Defects in Quality Control 101: Defect Types

At this point, you might be wondering how controllers are even able to categorize the different defect types. After all, there are countless industries and product varieties out there, and each comes with its unique challenges and requirements. Can one standardized categorization system do them all justice?

The answer is yes, but with an important caveat: while there are three main defect categories that are used across various industries, the classification system leaves a lot of room for customization. But more on that later.

For now, let’s take a look at the three main types of defects: minor, major, and critical.

Minor Defects

If a defect is classified as minor, that means the item does not comply fully with the product specs but is still usable. The defect does not affect the product’s marketability and functionality and only has a minimal impact on its appearance.

A minor defect is typically so tiny and insignificant that the end-user might not even notice it. And even if they do, they are not likely to return the item, request a refund, or decide against buying it.

Major Defects

Major defects are a different beast altogether. They are considered much more serious than minor ones. Not only do major defects cause items to depart significantly from the buyer specs, but they could also negatively impact the appearance, performance, and/or function of the faulty products.

What’s more, consumers are highly likely to notice major defects and return the item, ask for a refund, and even submit a complaint to your customer service department.

Critical Defects

Critical effects are called “critical” for a reason. They are the most serious defect type and typically render the product completely unusable.

Oftentimes, items with critical defects can also be a health and safety hazard to your staff, your customers, and even third parties. And if your products are a risk to people’s health, that means you are at risk of potential lawsuits and product recalls — to say nothing of the consequences for your brand’s reputation.

Handling Defects: Acceptable Quality Limits

It’s clear that if quality inspectors find critical effects in an item, you would have to discard the product or even the whole batch.

However, what’s less clear is what you should do with products with minor or major defects only. That decision is entirely up to you and depends on many factors, including:

  • The industry standards
  • The applicable regulatory framework
  • Your customer base
  • Your brand image
  • The product type

You need to consider all that and more to decide how many of each defect category you are willing to accept from your suppliers. Your tolerance for defects is also known as acceptable quality levels or acceptable quality limits (AQL). That is what the quality controllers will refer to when inspecting your products.

And if you are having difficulty defining your AQL yourself, you can always consult with your controllers. Most professional inspection companies will have detailed standards for both AQL and classification of defects in quality control for various product types. However, the ultimate responsibility for setting your AQL lies with you as the importer.

Useful Tips for Defining Your AQL

As a general rule, the more serious the defect, the lower your tolerance for it should be.

Many buyers have a zero-tolerance policy for critical defects. A single fault of this type will usually cause the item to fail the inspection and get recalled. Depending on the severity of the defect and the level of risk involved, the buyer may even cancel the whole order.

In contrast, there is normally a somewhat higher tolerance for minor and certain major defects. However, it is essential to set clear limits on the exact number and sub-types of defects you are willing to accept. Let your quality inspectors know that even minor defects could cause an item to fail the inspection if there are too many of them.

All that doesn’t go to say that you can’t have a zero-tolerance policy for minor issues, too — especially if you are serving higher-end customers or marketing your products as exclusive or premium-quality.

In any case, however, your goal should be to minimize defects as much as possible and expect a high standard of work from your quality inspectors.

Classification of Defects in Quality Control: Industry Examples

The same type of defect could be insignificant in some products but absolutely critical in others. Moreover, different materials are susceptible to different kinds of damage. That’s why it is important to consider the unique realities of your industry and target market when classifying defects and defining your AQL.

What follows are examples of what could constitute minor, major, and critical defects in four very different industries.

Electrical and Electronic Products

The electrical and electronic (E&E) product category includes any item that requires electricity to function: from household appliances and consumer electronics to children’s toys, power tools, personal care items, and more.

Removable, non-permanent surface marks are a classic example of what is typically considered a minor defect in E&E products. Think dirt, dust, excess glue, or anything that can be easily cleaned or wiped away. The vast majority of importers and consumers will not see that as an issue.

On the other hand, permanent marks and surface scratches are more likely to be seen as major defects. The same goes for issues relating to the performance of the product. Examples include malfunctions such as:

  • A faulty display
  • Poor connectivity
  • Failure to turn on or off

… as well as anything else that requires a rework of the software or hardware. Typically, the importer will have the product fixed, re-tested, and released back on the market.

In contrast, damaged or exposed wiring is nearly always a critical defect. Compromised wiring is a clear health and safety and fire hazard with potentially fatal consequences such as electric shock and electrocution.

Industrial Components

Industrial components include various types of machinery or materials specifically designed for industrial use. These include:

  • Gas valves
  • Conduit piping
  • Wind turbines
  • Fabricated steel
  • Maritime equipment

… and many more.

Like with E&E products, surface imperfections such as welding protrusions that don’t affect the functionality of the product are usually considered minor defects.

Minor deviances in non-critical dimensions that won’t impact the use or performance of the product will probably be seen as major, but still somewhat tolerable, defects.

However, rust and corrosion are almost never acceptable, as they are an indication of material degradation and potential product failure. Needless to say, that will be classified as a critical defect.


Softline products include various textile products such as:

  • Raw fabrics
  • Interior textiles
  • Garments
  • Footwear

As a result of the delicate raw materials and the labor-intensive production process that is only marginally automated, defects are a daily occurrence in the softline industry.

Fortunately, some of the more common ones, such as untrimmed threads or loosely sewn buttons, are only minor defects. They can be easily mended by the manufacturer, and the product will be as good as new. If you are selling higher-end garments, however, you — and your customer base — might not tolerate even such small defects.

Issues that visibly affect the appearance of the product and potentially jeopardize its quality will be seen as major defects. Missing stitches are a classic example, as they can impact the seam length and the structural integrity of the garment.

Forgotten needles in the products are, without a doubt, a critical issue. As this defect poses a clear danger to the end-user and anyone else handling the item, it should result in the product failing the inspection.


Hardline products are an incredibly broad range of items made of hard materials such as metal, plastic, or wood. Examples include furniture, cookware, sporting goods, building materials, and more.

Again, slight abrasions on the product surface resulting from rough handling or mishaps in the production process are usually a minor defect — as long as they don’t affect performance and functionality.

However, deeper scratches, as well as damage to a product’s logo, can be a major defect. Damaged logos are difficult to repair and can negatively impact consumer perception of your brand.

Common critical defects with hardline products include sharp points and protrusions on the surface of the items.

The Importance of Quality Control Checklists in Classification of Defects in Quality Control

To make the job of your inspectors easier and ensure full compliance with all your product specs, you need to have a quality control checklist.

A quality control checklist is a document that contains a detailed breakdown of your defect classifications. Your goal here is to create an exhaustive list of all potential minor, major, and critical defects with your product types.

The checklist should also include your tolerance or AQL for each defect type. It’s also a good idea to add important information, such as:

  • Required inspection equipment
  • On-site testing protocols
  • Packaging specs

… as well as anything else that could be of use during the quality control process.

Make sure to invest a lot of time and effort into your checklist. A detailed and comprehensive document will not only ensure accurate inspection results but could even help your supplier identify and correct defects even before the inspection.

It’s also important to regularly review and update your checklist, defect classifications, and AQL to reflect new developments in the industry or your business.

Addressing Quality Defects

Depending on the type, number, and severity of the defects, you can do one of the following:

  • Take no action, accept the faulty product, and release it on the market
  • Ask the manufacturer to correct the defect(s) through product rework
  • Recall the goods and request a replacement from the supplier

If you choose to have the defective items reworked, don’t forget to run a second inspection afterward to ensure that they now comply with your specifications. Depending on the severity of the issue, you may consider charging your supplier for any reinspections and the associated delays.

If the defects are critical and a potential health and safety hazard, it’s also recommended to destroy any faulty products to prevent them from reaching consumers through the black market.

Classification of Defects in Quality Control: Final Thoughts

The classification of defects in quality control is a vital step in the inspection process. A well-thought-out defect categorization can greatly improve quality control, cut down your losses, and boost customer satisfaction.

While the responsibility for creating a thorough defect classification system ultimately lies with you, an experienced quality control service provider can be of great help. Quality inspectors are intimately familiar with the industries they specialize in. That means they can offer valuable insight into common defect types, product specifications, applicable regulations, and more.

Here is where we come in.

Jonble is China’s leading independent quality control provider. Our experts can help you with the classification of defects in quality control and developing your AQL. We will then carefully inspect your products to ensure that they conform fully to your specifications and your customer’s expectations. For more information on our services, browse our website or get in touch.