Sampling Plans & Control of Nonconforming Product

Jim Wynne

Staff member
Admin
#21
Tim Folkerts said:
I wouldn't say its a question of caring vs not caring, but rather a question of how much I care. I care enough about deer in the road to wear a seat belt, but not enough to stay at home. It's a balance.

Similarly for bad parts. There are cases where paying less is worth a few bad parts in a lot. There are cases where paying for inspection is worth avoiding unusually bad lots.

Just my $0.02


Tim F
Tim, I understand, trust me, but what you're talking about has nothing whatsoever to do with my question. In the case in point, a decision has been made to do screening inspection. This means that someone is concerned about bad parts getting into stock or production (what other reason could there be to do the inspection?). The OP informs us that after defectives are found, if the number of defectives is lower than the AQL limit, the lot is accepted without further screening even though the lot "probably" contains more defectives.
So.
Why do the inspection in the first place if you're OK with sending bad parts to production? Asked another way: What is the purpose of the inspection if you're willing to send bad parts to production?
 
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Tim Folkerts

Super Moderator
#22
Jim Wynne said:
Why do the inspection in the first place if you're OK with sending bad parts to production? Asked another way: What is the purpose of the inspection if you're willing to send bad parts to production?
The purpose of inspection isn't to verify that the lot has just a few bad parts.
The purpose is to verify that the lot isn't outrageously awful.

For every slightly bad (but still acceptable) lot, inspection is a waste of time and money. You use manpower, you reject some lots that really aren't too bad - and in the end the product is just as good (or bad) as if you hadn't done the inspection. I agree with you 100% that this is worthless.

For every truly awful lot, however, the inspection may well be advantageous. A really bad lot could easily wipe out the profit of 10 or 20 good lots. If you have no profits for a month because of one bad day, it could well be worth a few dollars per day of inspections costs as insurance against losing the month's profits!

For every acceptable lot inspected, you lose a little money. For every awful lot inspected, you save a LOT of money. Estimates of costs, rates, etc would be needed to decide in specific cases whether the savings exceeds the costs.


I think this is getting more directly at your central issue. :yes:? :nope:?



Tim F
 
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