Designing a Mil-Std-105 or ANSI/ASQ Z1.4 Sampling Plan

[johnnybegood]

We have a production with a run rate of 1k per shift. Production manually assemble the product and have it tested electrically at test station. Before the product is send for packing, Production will 100% visually inspect for mechanical/cosmetic defect. QA inspector will do sampling buy-off electrical and mechanical/cosmetic.
The product does not come to QA in a constant rate. My question is how do I generate a correct sampling plan? Customer goal is 0.08dphu

[howste]

I'd probably set up a sampling plan based on ANSI/ASQ Z1.4 since it sounds like you're doing attribute sampling. MIL-STD-105E is equivalent to that standard, and you can download it free: Free Military Standards.

[Al Dyer]

Yes,

105-E is very good and there is also a good one in Juran. The important aspect, in my opinion, is that these guidelines and tables can be modified from their original content to work with any company specific situation.

The thing is not where it is from, but if it works.

Great guidelines

Al...

[johnnybegood]

How to set or determine the AQL and which inspection level?

[howste]

Originally posted by johnnybegood
How to set or determine the AQL and which inspection level?

From MIL-STD-105E page 2:

Use of a value of AQL for a certain defect or group of defects indicates that the sampling plan will accept the great majority of the lots or batches provided the process average level of percent defective (or defects per hundred units) in these lots or batches be no greater than the designated value of AQL.

So what you want to do is find the AQL closest to your customer's requested AQL (which is the same as DPHU) of 0.08. The options you have are 0.063 or 0.10. I'd probably play it safe and pick 0.063. You can look at the OC curves in the standard to see if it makes sense.

Normally inspection Level II is used. Other levels can be used depending on the sampling risk.

[johnnybegood]

Let say my customer does not spell out the dpku goal. Now how do I set a sampling plan then? I really do not know where and how to start.

Originally Posted by howste

From MIL-STD-105E page 2:


So what you want to do is find the AQL closest to your customer's requested AQL (which is the same as DPHU) of 0.08. The options you have are 0.063 or 0.10. I'd probably play it safe and pick 0.063. You can look at the OC curves in the standard to see if it makes sense.

Normally inspection Level II is used. Other levels can be used depending on the sampling risk.

[Sam]

Food for thought;
If production is already doing the testing and visual inspection, what is the need for an additional QA inspection?

[johnnybegood]

Originally Posted by Sam

Food for thought;
If production is already doing the testing and visual inspection, what is the need for an additional QA inspection?

call it escapee.......Production may not be testing/visual inspection 100% eventhough they are suppose to do so. Visual inspection are manually human dependent thus defect may skip thru.