If you’re an importer located thousands of miles away from your manufacturer, among the plethora of things that might keep you awake at night is the quality of the products that are being produced for you. Due to the fact that you cannot physically inspect the products yourself or overview the production process, you are bound to have reservations about the quality of the shipment that you are expected to receive.
Important Note:
Keeping this in mind, it is equally important to set quantifiable standards regarding what constitutes the minimum acceptable standards of quality for your business. This will not only give the manufacturers a precise picture of what you expect from them, but will also aid you in making sure that there is no arbitrary selection of products that pass the product quality inspection and that each and every product maintains the same kind of baseline quality standards so that your business’s integrity and reputation is not compromised by selling faulty or below average quality products.
Using an AQL (acceptable quality limit) as the basis for setting a maximum level of tolerance for defects helps to solve this problem. This also serves another huge advantage which is inspecting samples rather than the entire shipment. Although it sounds more promising to check each and every product to ensure that quality is met, AQL allows for a systematic method through which samples can be selected and then inspected that are likely to adequately reflect the entire shipment.
If you take a look at the AQL table, it may appear to be extremely overwhelming and difficult to grasp. For an importer with minimal knowledge of the mathematical and statistical insight that goes into the making and reading of the AQL table, you may find the table overly complex. But you need not worry anymore- the following article will help you grasp a straightforward understanding that is required for practical usage of this table.
1. Acceptance Sampling
As mentioned earlier, the AQL table allows you to choose a sample to inspect rather than each and every product that forms part of the shipment. Even if your keen interest in maintaining quality compels you to check each product in the delivery, there are two main reasons why you should not do so and instead work with a sample instead:
- Wastage of time and energy: not only is inspecting each product in the order extremely time-consuming, resulting in a wastage of energy of the employees that are responsible for inspecting every piece of the product who could have otherwise been involved in more productive tasks.
- Destructive product sampling: if testing a product requires its wastage, such as in the case of bullets, then testing every item would be pretty much pointless. In such case too it is particularly important to use a sample.
The statistical inferences behind AQL work in such a way that even if the lot size increases, a relatively small sample size would provide results that would still be statistically significant. Therefore, you can decide to inspect 10-20% of your sample size that would not only decrease cost and energy put into the inspection process but will also save a considerable amount of time so that your products can reach the end consumer quicker.
2. Acceptable Quality Level
As mentioned earlier, the acceptable quality level is the minimum quality standards that products in delivery must exhibit if it is to pass inspection and be cleared for sale to the final consumer. The AQL typically ranges from a scale of 0 to 15, although it is rather unconventional to use a value of AQL higher than 6.5– because the higher the acceptable quality level, the more would be your tolerance towards any defects found in the delivery.
The AQL table is used widely by quality control professionals all around the world so that uniform quality measures can be achieved.
This table tells you:
- the appropriate number of units to pull for inspection
- your sample size
- the number of defects that would be acceptable in that sample
It is inevitable to find some sort of defects in your shipment because it is rather difficult to find any factory in the world that produces absolutely perfect products. However, this does not imply that you should compromise on quality standards for your products. Keeping this in mind, it also important to note that not every aspect of the product will hold the same importance in terms of quality assurance: this is why you might want to make use of different AQLs to different types of quality defects.
What happens if your product does not meet your AQL?
Once you’ve made clear the minimum quality standards that you expect from your shipment, it is the manufacturer’s responsibility to make sure that he produces products that at least comply with these minimum standards. However, if during inspection you find that the products do not meet with given standards than you can take one of the following measures:
- Ask the supplier to fix the defects in the products
- Ask for the replacement of the defected items
- Asking the supplier for compensation against the unusable goods
- Make sure to destroy any units that the supplier can sell-off in the black market for a lower price
Depending upon the severity of the issue in the shipment, one of these approaches would be suitable for you as a remedy to the low-quality products.
3. ANSI ASQ Z1.4
The ANS ASQ Z1.4 was developed by the American National Standards Institute and American Society for Quality, and it’s the most widely used standard for AQL sampling around the world.
- The U.S FDA recognizes this standard as being applicable for single, double and multiple level sampling plans.
- In a single sampling plan, quality inspectors pull out only one random sample and then make a report based on the quality levels of that sample product.
- This standard is based around inspecting attributes under two categories: conforming and non-conforming to given requirements
- Sample standard deviation measures the degree of nonconformance
4. General Inspection level
We will now look at how you can use the AQL table for inspection.
Inspection levels are used to determine the sample size from among the entire shipment that the quality inspector will actually examine. You need to know the following information in order to be able to use the AQL table:
- Lot size
- Total order quantity
- General inspection levels: checks for appearance, assembly, and functionality
The general inspection level will be most commonly divided into three levels depending upon the scope of the inspection that has to be carried out:
- GI is the budget option that costs you the least amount of time and money, the smallest sample size available for your lot size
- GII – the “middle-ground” option that balances time and cost with transparency, this is the most common inspection level for importers
- GIII – the largest sample size available for your lot size, this offers the most transparency into your order’s quality and takes the most time to inspect
5. Special inspection level
A special inspection level, in comparison to a general inspection level, is carried out on a sample size that is much smaller than that used in the general inspection level because this is likely to take much longer and require greater resources in terms of the costs incurred. An example of cases where you would want to use a special inspection level is one of the following cases:
- Are destructive to the product, like a fabric GSM test that involves cutting out a piece of fabric from the sample
- Are expensive and/or time consuming to conduct, like a battery charging test for electronic devices
- Tend to yield similar results across all units, like measuring the dimensions of injection-molded components that don’t vary appreciably in size from one unit to the next
Depending upon the significance that you attach to your test, you might want to vary the sample size. This is very similar to the general inspection levels where S4 will portray the largest sample size and S1 will portray the smallest. If you attach greater importance to the results of the test that you want to carry out, then you might want to use a larger sample size.
6. Critical defect
You can understand the severity of a critical defect by keeping in mind that importers often attach an AQL value of 0.0 for critical defects, which basically means zero tolerance. This implies that even if there is one critical defect found, inspectors will reject the entire sample. A critical defect will invariably impact the functionality of the entire product, which is why a defect in this area cannot be ignored.
QC professionals are most likely to classify the following as a critical defect:
- The product poses a threat to the safety of the consumer
- The defect makes the product unusable
- Results in the product being frequently recalled
Because these defects are likely to significantly impact the business in an adverse manner if a critical defect is found the shipment will be stopped and all the faulty products replaced. Another inspection will then be carried out to make sure no critical defects remain, and only when the QC professionals are satisfied will the shipment be passed.
7. Major defect
A major defect is not as serious as a critical defect, but still directly impacts the functionality of the product so is a major concern. But unlike a critical defect, there is some margin where a sample with some major defects will be passed. An AQL value of around 2.5 is common for major defects. The following are examples of flaws that are considered major:
- Adversely affects the performance of a product
- Varies significantly from product specifications
- Would likely cause the end customer to return the product
Because major defects are not likely to cause danger to consumers, they can be acceptable in a sample but only in a very small amount. However, even if they do not physically damage the consumer they still might damage consumer expectations and satisfaction as related to the product. Hence if goods are found to have major defects that exceed the AQL you have set, the manufacturer is responsible for repair and replacement of the defected products.
8. Minor defects
A minor defect is the least serious among the three categories of defects. However, this does not mean that minor defects do not harm the integrity of your business. For this reason, there is still a threshold for how many minor defects are acceptable in a sample by setting an AQL level- typically of around 3.5-4.0.
Commonly, a minor defect may encompass the following:
- Not directly impacting the product’s functionality
- Not noticeable to the customer during the unpacking of the product
- Does not result in a customer returning the product
However, it is important to remember that even though minor defects do not result in recalling of the product, they are not a good sign for the future of the business. They might result in bringing distaste to the consumer, who would then consider switching to a different brand the next time he makes a similar purchase.
It is also noteworthy that some defects may be classified as either minor or major depending upon their severity. For example, a scratch on a vase of less than 1mm will be a minor defect, whereas one larger than that will be a major defect.
9. Acceptance point
This is the maximum number of defects that are acceptable in a given sample size at a specific AQL in order to not reject an order. Just as importers have the leverage of choosing their own AQL for each defect class, they can also choose their own acceptance point depending upon the service and quality that they might want to offer their consumers.
It is common to see higher acceptance point for minor defects, lower for major, and then lowest for critical defects depending upon the AQL values they choose.
10. Rejection point
This is denoted as ‘Re’ in the AQL table, indicating the minimum number of defects that given sample size will have at a given AQL that will result in rejecting the order. It is common to see the rejection point usually one value higher than the acceptance point.
If the number of defects found equal or exceed the rejection point, the shipment will not be termed as fit to use. This would cause the importers to reject the shipment and ask the manufacturer to either repair or replace the defected products.
Conclusion
It is important to keep in mind that any kind of sampling will come with its risk no matter how meticulously you draw out the sample. However, making use of an acceptable sampling like AQL gives you the advantage of using limited time and resources in order to inspect the shipment that usually yields results that are similar to those when inspecting each sample individually.