Establishing an effective product inspection frequency is tricky. When combined with ISO (International Organization of Standards) 2859-1 it becomes even more difficult to inspect products.
As companies reliant on supply chains know, having a balance between ensuring an accurate representation of their product batch and maximizing the time and money spent on inspections, is critical to success.
In this article, we'll look at what ISO 2859-1 standard is, how it works, and how it helps companies address the challenges that come with batch inspections.
The standard's full title is "ISO 2859-1: Sampling procedures for inspection by attributes — Part 1: Sampling schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection."
Simply put, this standard helps companies determine:
However, determining these values are not that simple. A variety of factors can influence these percentages and threshold numbers.
Four Common Factors that Affect Sampling Frequency
1. Batch size. A 100% product batch check, with 20 or 50 units, might not be too time-consuming for an inspector to complete in a day. However, a batch containing thousands of units might require a week (or more) for a 100% check--a length of time which is not often viable for a company.
2. Product attributes. The product attributes, or makeup of the product, determines the difficulty level of sampling. In turn, this affects the sampling frequency.
For example, a batch of garments may be faster to inspect for flaws (e.g., asymmetrical sleeves and collars) than a batch of electronics that is inspected for restricted substances.
For the garment, a quick tape measurement is used to spot the flaw. For the electronics, a more complex X-Ray test might be required.
3. Destructive testing. Some inspection tests destroy the product in the process. Therefore, a greatly reduced sampling frequency would be more feasible.
4. Supplier reputation. Sampling frequency can be adjusted based on a supplier's history of inspection checks. It can be lowered for suppliers that deliver quality goods consistently...and raised for those that don't.
Adjusted sampling frequencies can be an effective incentive for your suppliers.
The ISO 2859-1 standard includes a statistical sampling scheme, which categorizes sampling frequencies into inspection levels. These inspection levels are combined with an Acceptable Quality Limit (AQL) value and organized into tables. (You can see the ISO 2859-1 tables here.)
Acceptable Quality Limit (AQL)
The AQL is a threshold number of product failures within a total number sampled that renders the entire batch a failure if breached.
Inspection Level Categories
There are three General Inspection Levels (Level I, II, III) and four Special Inspection Levels (S1, 2, 3, 4).
General Inspection Level frequency increases per level, with L II considered to be the default level for normal inspection.
(An L III frequency might be applied if there have been recent problems with a supplier.)
Special Inspection Levels are much lower than General Inspection Levels. They are often used for products that require a much longer inspection time per unit or require the sampled product to be destroyed in the inspection process.
Experienced, product-specific inspection services can help you determine the appropriate inspection level and AQL to suit your specialized product.
Firstly, the ISO 2859-1 provides inspectors with standard guidelines for inspection--so that all companies receive inspection and AQL values that are based on measurements that best represents the quality of the entire batch.
Secondly, the ISO 2859-1 tables provide an easy-to-follow playbook after the complex process of frequency determination has been completed.
Thirdly, the ISO 2859-1 addresses the practical side of batch sampling. If time wasn't a factor, then a batch of any product could be 100% inspected.
However, in reality, depending on the product, a high sample percentage could take an inspector several (costly) days to finish.
Furthermore, inspecting 100% of the given batch may not necessarily tell an inspector more about your product's overall quality.
Under the eye of a good inspector, a recurring product fault can reveal a solitary production issue without the need to inspect every unit.
QIMA inspectors apply the ISO 2859-1 standard to all sampling inspections.
Furthermore, QIMA's product experts can help your company establish a sampling frequency and AQL based on all relevant factors.
Finally, QIMA inspectors can be on-site at any factory around the world within 48 hours, so that your product needn't waste valuable time waiting to be tested.
Ready to schedule your ISO 2859-1 standard product inspection?
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