Hi, all.

I work in a batch-driven shop with lot sizes between 8 and 10K pieces. Our final inspection/packaging involves 100% visual for assorted defects. I am looking to build in automation so when scrap for a given defect reaches a specific level (bogie), the inspector and myself are notified that additional measures are necessary.

I have the 2003 version of Z1.4 but, of course, many of the plans are dependent on sample size. When our sampling is 100%, these do not apply. Is there another table within the standard that I could refer to in determining the amount of defects that would trigger the alarm noted above?

Thanks!

Can any of you help with this? My appreciation in advance!

Further research into the application of an Acceptable Quality Level (AQL) has been a challenge as this value is based on sampling for attribute characteristics. AQL was originally defined by MIL-STD-105E. Given that we're already 100% visually inspecting these parts, AQL does not have much value. I have found little else insofar as a specification or standard to aid in making this determination as all are dependent upon either variable characteristics or sampling methodology. On that note, please see later in my description which follows that I reference AQL for guidance purposes in this issue.

I have looked to apply a percent non-conforming for any given defect which would require 200% inspection. Of the orders we had third-party inspected (at our cost) for a given attribute defect, we had previously picked out 1.20% of the combined total pieces at our final inspection operation. As 13 known parts exceeding specification were found by third-party sorting, 1.20% is too high a value to set as the threshold for 200% inspection/re-inspection.

In discussing this with a senior inspector and assuming an order quantity of > 10,001 pieces, 50 pieces scrap for the defect in question (as a threshold value) should necessitate 200% inspection or 0.5% (or an AQL of 0.5) in her opinion. This puts us between two Special Inspection levels, S-3 and S-4 per MIL-STD-105E. When accounting for > 10,001 piece order quantities, S-3 has an AQL of 0.65 and S-4 an AQL of 0.25. S-3 assumes a sample size of 20 and S-4 assumes a sample size of 50. Again, we are 100% visually inspecting these parts so the AQL does not really apply.

My proposal, therefore, is to require 200% of orders wherein defects/part scrapped under scrap codes for the defect in this matter (or others) go above 0.65% of the incoming quantity. This conforms with the 0.65 AQL inspection level S-3 and is closest to the inspector's opinion cited above. 0.65% is nearly half of the 1.20% as discussed above, as well. Pieces constituting the quantity required for re-inspection shall be out of the known specification we have referenced in this matter.

Unless someone else has something, this is what I'm proposing in order to move forward with this issue.