Quality Control: What is AQL?
Because ideas about quality vary between people, buyers need a standardized way to judge the quality of their goods. This is where the AQL comes into play.
‘AQL’ stands for ‘Acceptance Quality Limit’ or ‘Acceptance Quality Level’ and sets the international quality standard for product inspections. It helps determine your inspection sampling size according to your order quantity and your product quality tolerance level.
Through the use of Statistical Sampling, inspectors and buyers can determine the overall quality acceptance of a production lot without having to check every single item. This saves buyers time and money, while still providing an accurate estimate of their overall production quality.
In table A you can see:
Lot/Batch sizes: A lot or batch is named after your collection of products, from which a sample will be pulled.
Special Inspection Levels: Special Levels consist of S-1, S-2, S-3 and S-4 and are used in cases where only very limited number of samples can be checked. Some of these scenarios may include a buyer requiring more packages inspected on only a few cartons, or time-consuming tests that require samples to be disassembled or destroyed.
General Inspection Levels: This represents the general accuracy level of the Sampling Method. There are three General Sampling Levels: II, III, and I.
Level-I requires a smaller sample size, and helps decrease inspection time, but raises the likelihood of defects not getting caught. You may consider using Level 1 inspection if you feel confident with your supplier or they have consistently delivered good product quality.
Tip: Many buyers will feel tempted to skip through inspections in an effort to save a few bucks. Instead, buyers can opt to check fewer samples by using a level-I inspection.
L-II is the most common inspection level. This level covers a relatively large inspection scope without forcing buyers to go over budget.
Level-III uses a larger sample size, significantly increasing the time to perform inspection, while increasing the probability of catching any defects.
Tip: This option is highly suggested when a supplier has a history of quality problems.
In Table B you will see:
Sample Size Code Letter: The sample code letter is based on lot size and inspection level. Sample size code letters and the corresponding AQL level designate sample sizes.
Sampling Size: The sampling size is the total number of units to be inspected.
AQL and Defect Classification: Let’s face it, defects will be found in almost every production lot. Buyers can regulate the overall quality of their goods by arranging their AQLs for critical, major, and minor defects.
Critical Defect: Any condition with the possibility to cause harm or injury to the consumer.
Major Defect: Any condition which can affect the product’s marketability, sale-ability, or function, which can result in the consumer returning the product.
Minor Defect: Any condition, which may be less than desirable to the consumer. The defect does not negatively impact marketability or function and is not likely to result in the product being returned.
Now that you know the basics, let’s go over and apply what we covered.
Example: Hiking Sticks
Let’s use a hypothetical order of 7,000 Hiking Sticks.
Determine the Lot Size:
First off, we need to identify the order quantity by referring to the AQL Chart, Table A.
Knowing our quantity is 7,000 pcs we can see that our order quantity falls in the between 3,201 and 10,000
Next, we need to decide what inspection level to use.
If you look to the right, you have two inspection levels to choose from:
Special levels: S1->C, S2->D, S3->F, S4->G and General Inspection Levels: G1 -> J, G2 -> L, and G3 -> M.
Let’s stick with the General Inspection levels, as this is the standard AQL sampling plan used by default for conducting normal product inspections.
Up next, we have the choice of General inspections I, II and III. Level III is the strictest testing and Level I, the most lenient.
We will use AQL Standard Level II, as this is standard for consumer products – it’s also the minimum sampling size you should inspect to minimize your risks.
Table A indicates our sample size code letter should be L, which directs us to Table B, which indicates our sample size should be 200 units.
On the top of AQL Table B you will see defect levels ranging from 0.065 to 6.5, with the strictest parameters on the left and more lenient parameters on the right.
You also have a row with “Ac,” meaning Accepted levels and “Re,” meaning Rejected levels.
You can select which level to use based on defects: critical, major and minor. We will be using Major 2.5/Minor 4, which most buyers will typically use for most consumer products.
Note: There is no universal rule about AQL requirements. With that in mind, strict AQL requirements can increase the pricing from your supplier; this is due to higher production and rework costs on your supplier.
Setting your quality requirements too high may influence suppliers to refuse to manufacture your products, as they will view your AQL requirements as too stringent or unreasonable. It’s best to work out your requirements with the suppliers prior to the start of production.
According to our quality standards for Critical 0, Major 2.5, and Minor 4:
|Major defect acceptable standard is 10 pcs||Major defect acceptable standard is 11 pcs|
|Minor defect acceptable standard is 14 pcs||Minor defect acceptable standard is 15 pcs|
Any major defects over 10pcs or the minor defects over 14pcs, will result in a failed production lot.
With an understanding of AQL tables, buyers can plan and negotiate their overseas production with confidence and accuracy.
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