What is AQL?
AQL stands for Acceptable Quality Limit, and it is a statistical method used in quality control to determine the sample size and the acceptance criteria for product quality inspections.
What is the benefit of AQL?
AQL helps buyers and suppliers to agree on a quality level that is acceptable for both parties, and to reduce the risk of receiving or delivering defective products. It provides a balance between quality assurance and cost efficiency.
What are the limitations of AQL?
AQL assumes that the quality of the batch is homogeneous and follows a normal distribution due to mass production. However, this may not be true in some cases, such as when the batch has quality variations or outliers. Please consult your inspection company to assess if AQL methodology is suitable for your product.
AQL only provides a reasonable assurance based on a sample randomly selected from the batch, and there is always a certain probability of making a wrong decision based on the sample. The SOP (standard operating procedure) of an inspection company to pick samples from carton is a crucial step to make sure randomness.
What are the main components of AQL?
The lot size: This is the total number of units in a batch of products that need to be inspected. This is usually the total quantities in your Purchase Order.
The inspection level: This is the level of thoroughness of the inspection, which affects the sample size. There are different inspection levels, such as general, special, or reduced, depending on the type and importance of the product. A higher inspection level means a larger sample size and a more stringent inspection.
The AQL value: This is the maximum percentage of defective units that is considered acceptable for a batch to pass inspection. There are different AQL values, such as 0.65, 1.5, 2.5, 4.0, etc., depending on the severity and classification of the defects. A lower AQL value means a lower defect rate and a more stringent inspection. For example, major defects are usually assigned a lower AQL value than minor defects.
How do we interpret defects in ECQA?
We interpret defects in three categories:
Critical defect: a defect that fails to meet mandatory regulatory requirements and affect the safety of consumer/end user. For example:
sharp edge that can hurt the hand are found on the product.
insects, bloodstains, mold spots
broken needles on the textile
electrical appliances fail the high-voltage test (easy to get electric shock)
Major defect: a defect that cause product failure and affect the usability and salability of a product. For example:
the product assembly is fail, causing the assembly to be unstable and unusable.
oil stains
dirty spots
function use is not smooth
surface treatment is not good
the workmanship is defective
Minor defect: a defect that cannot meet the buyer’s quality expectation, but it does not affect the usability and salability of a product. For example:
small oil stains
small dirt spots
thread end
scratches
small bumps
*Note: the market perception of a brand is one of the factors determining the severity of defect.
How do you decide the inspection level and the AQL value?
The buyer and the supplier should always agree on the inspection level and the AQL value before the inspection and communicate them clearly to the inspector.
The common practice for consumer goods is to apply General Inspection Level II for visual check and simple function test, Special Inspection Level I for measurements and performance testing.
For general consumer products inspection, AQL value is usually set at 2.5 for major defects and 4.0 for minor defects, and a zero tolerance for critical defect.
How do I read the tables of inspection level and AQL value?
Step 1: Find out the lot size/batch size
Step 2: Based on the lot size/batch size and Inspection Level, get the Code Letter of Sample Size
Step 3: Find out the Sample Size based on the Code Letter
Step 4: Find out the Ac (Acceptable quantity unit) based on the AQL Value
Post time: Nov-24-2023