# Incomming inspection - is the material pure or plated? - 50000 units

Discussion in 'Sampling, Standards and Inspection' started by QualityMan, Jan 14, 2020.

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1. ### QualityManMember

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Hi,
My supplier says he put the wrong labels on a lot of 50000 small metal parts.
They are named plated instead of pure. but, I ordered pure, and the suppliers says they are pure. But I want to make an incomming inspection, to verify if the suppliers tells the truth.

Visually they look 100% the same. Only using a magnet, can I tell the difference between plated and pure.
The parts come in plastic bags of 2000 pieces, so I have 25 bags.

I consider it a critial error if, I find a plated part, in any of the bags.

1) If I only take 2 samples out of each bag, what level of certainty will that give me - if they all are pure like they are supposed to be?

2) So, what is the smallest possible sample size I can take, to verify with statistical significance the content of my bags?

QualityMan

2. ### Andy NicholsModeratorStaff Member

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Does this help?

3. ### Pau CalvoNew Member

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Maybe it sound dumb but why not 100% inspection taking advantage of the magnetic properties, if are magnetic enough you just need a box and a magnet...

If works you will eliminate the risk of sampling.

4. ### QualityManMember

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Hi,
Andy: Looks interesting. I was only aware of AQL, so Zero sampling is new to me.
Will you be so kind, and elaborate a bit on the columns 0.4, 1.0 and 4.0. It is critical, major and minor?
So, red arrow (0.4) gives 123 samples. So, what kind of probability does is give, that my 50.000 parts are all nickel, if I find no faulty units in my sample?

Pau: Well, unfortunately both materials repond to a magnet. However, the plated sticks more than the pure!
Maybe there is an instrument, which can measure this? so I can tell the difference by fact, and not on a subjective basis with regards to stickyness.

Best regards
QualityMan

5. ### Pau CalvoNew Member

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Just as an idea; if you have this kind of small parts you may have a dispenser for the assembly, like a vibro or a ramp.
Talk with your process department maybe they have an idea to use the magnetic properties to discard the parts that are more affected by the magnetic field.

For me if it is critical that this component has to be plated you will have a high risk with a sample sorting.

6. ### Eric TwinameWell-Known Member

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How critical is it?
If critical, it sounds like a good job for a temp worker for a couple days.

"Here's a magnet...stick it to every part...if it doesn't stick to one, come show me immediately and I'll give you \$50 cash on the spot."

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