What is a good Sampling Plan for LARGE Lots of Supplier Components

#1
I'm hoping someone here can provide a solution. My problem is that I receive large lots of components from suppliers. Generally upwards of 35,000 pcs per lot. I consume these 35,000 pcs in anywhere from 3 days to 5 days. The AQL Sampling Plan I have tells me (at 1.0) to sample upwards of 60 pcs per lot. I have to measure from 15 to 30 dimensions per part to determine if the part is in spec or not. This is super time consuming and the personnel have enough time to do it.
Example: If I receive a shipment today, 14 different part numbers, all large lots. My AQL says that I should inspect 60-90 depending on which lot I select. When I calculate it all out.... I would have to inspect 14 x 75 (avg) = over 1000 pieces. Each of those pieces have 5-10 dims to measure and document. I don't have the time or resources to inspect at that level.

I continue to find bad components in my processes and I know I need to do something. HELP PLEASE!!!
 
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apestate

Quite Involved in Discussions
#2
per ANSI Z1.4-2003, sampling for inspection by attributes, you can classify certain characteristics in terms of their quality or economic effects.

Essentially the question are all of the features you inspect on each part critical?

The standard accepts using different acceptance criteria for different classes of part specifications. The sample size is the same, but you can tolerate higher acceptance numbers for features that are less critical in nature.

You could also try acceptance sampling by variables which reduces the sample size significantly.

From ANSI Z1.4-2003 6.1

"The purpose of this standard is, through the economic and psychological pressure of lot non-acceptance, to induce a supplier to maintain a process average at least as good as the specified AQL while at the same time providing an upper limit on the consideration of the consumer's risk of accepting occasional poor lots. The standard is not intended as a procedure for estimating lot quality or for segregating lots."

The same sample size problem is apparent with any quantities. Acceptance sampling sucks to deal with, and in my opinion is right there at the bottom of the barrel just above 100% inspection.

In the end, you need to work with the supplier to lower the amount of nonconforming products. If you can't tolerate the defects, and have no way of catching every single defect as you consume them, you simply need to have the supplier enact measures to reduce the number of defects. This departs from acceptance sampling and enters the world of SPC and zero defect methodologies.
 

apestate

Quite Involved in Discussions
#3
BTW this board always wants to know details. ;>

What kind of parts are they? Plastic? Metal? Assemblies?

How many specifications of each component are show stoppers if they're out of tolerance? Can the tolerance be relaxed?

How many suppliers are you working with here? What types of businesses are they? Where are they at?

How are the bad components showing up? Floor personnel noticing them? Down machines, or maybe customer complaints?

Your question really gets to the core of what we all do.
 

Golfman25

Trusted Information Resource
#4
I would try to reduce the number of dimensions you need to check. Is it really necessary to check all 15-30 dimensions on each part? If only 1 or 2 dimensions are giving you the problems, then focus on those. Bring the rest of the part into spec. with a pencil. Good luck.
 

reynald

Quite Involved in Discussions
#5
I would have to inspect 14 x 75 (avg) = over 1000 pieces. Each of those pieces have 5-10 dims to measure and document. I don't have the time or resources to inspect at that level.

I continue to find bad components in my processes and I know I need to do something. HELP PLEASE!!!
Well just an idea:
Arrange the check items by order of which occurs the most (Pareto).
Check them first, and if you find defects/defectives you dont have to inspect/measure all other dimensions by return them to the suppliers.
 

apestate

Quite Involved in Discussions
#6
What kind of actions can you initiate for remediation, too?

Has your company been successful in the past with efforts to fix?
 

harry

Super Moderator
#7
I continue to find bad components in my processes and I know I need to do something. HELP PLEASE!!!
What's your agreement with your supplier on this issue? Looks like they are not doing a good job. You may want to look into actions to tighten it from their side.
 
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