Sampling
Ben Osburn
16 Posts

Hello quality experts,

Question for you all. If a defect is spotted after is a products and its entire production lot is made, is it necessary top do a 100% inspection for the rest of the lot?

6 Replies
Duke Okes
256 Posts

@Ben Osburn

  • Who is the customer for whom the product has been produced, and how would they answer the question?
  • What is the nature of the defect and what is the potential impact?
  • Was the defect found using a statistically based sampling plan, and if so, what does that sampling plan say you should do?
Vera Mulbah
16 Posts

@Ben Osburn, I think it might also depend on the machines or tooling used. if the devices or tooling used are different, it might make sense to do a 100% inspection. But if they are the same, it might be best to do maybe a 10% lot check.

For example, one machine was programmed to run the entire work order. In this case, if one part is defective, there is a high chance all other parts from that machine is defective too. for this scenario, a 10% lot check might do best.

Jay Arthur
23 Posts

@Ben Osburn
What is the customer's acceptable quality level (AQL)? If it's zero, you've already failed. If it's higher, you can use AQL tables to determine the desired sample size.

@Ben Osburn

Your question is a good one but in the manner to which it is asked it leaves much more unanswered than questioned.

As @Duke Okes started to point out, we need to know more about the product itself, the customer, and the end-use of the product to help ascertain whether additional sampling may be necessary.

As @Vera Mulbah points out as well, the process utilized could significantly impact the need here as well. If this product is mass produced and there are different machines producing it, we may need to analyze one set and not another. If the product is not mass produced but hand produced, then how many operators are involved and what is that variability?

Further, the simple concept of ‘form, fit, and function' still comes into play here. With that, how severe is the defect? Has this defect been analyzed for severity yet? Also, was this a simple singular component or a more complex assembly with multiple components? A complex assembly might have had the defect captured on a lower-level component already and previously analyzed, a capable QMSS would have shown this to you in the configuration analysis.

So, I think we need to know more before a complete answer can be provided.

Ajoy Basu
5 Posts

Ben,

The highest risk associated of the product will dictate acceptable AQL level and corresponding sampling plan. If risk is high, the acceptable AQL level is low and the sampling plan is typically reject on ≥ 1. In these instances you may have option of saving the lot with 100% inspection if approved by the customer.

Usually medium and low risk have sampling plans (i.e. higher AQL levels) that allow for a few defects. The allowable AQL level is determined by your customer.

ajoy

Vera Mulbah
16 Posts

In line with you, @Franklin Hutto