Sampling Plans and Cpk - Ways to Calculate the Sample Quantity

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Ricardo SKF INTERN

Re: Sampling plans and Cpk - Some way to calculate the sample quantity

Hello Bob,

I’m sorry for taking so long to reply.

I ended up using the confidence limits of Cpk to calculate the minimum n for an expected Observed Cpk (Kushler, R.H. and Hurley, P. "Confidence Bounds for Capability Indices." Journal of Quality Technology 24, 1992, 216–231).

I read some about the Xhi-LoR charts you suggested but I didn't propose them because it was a matter of interests and I had to work with restrictions and make things with what was told me.

Now that I have ended that task I’m going to analyze your suggestion.

What do you mean by run? (I'm sorry, I’m not native English speaker and sometimes I may confuse technical terms)

Best regards,

Ricardo.
 
R

Ricardo SKF INTERN

Re: Sampling plans and Cpk - Some way to calculate the sample quantity

The grinding process stops only for:

Tooling
Change of type of product

Otherwise machines are on continuous production.

An example before tooling (shorter period) is more or less 3 days non stop.
 

bobdoering

Stop X-bar/R Madness!!
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Re: Sampling plans and Cpk - Some way to calculate the sample quantity

The grinding process stops only for:

Tooling
Change of type of product

Otherwise machines are on continuous production.

An example before tooling (shorter period) is more or less 3 days non stop.

Great - if that is the case you should see a slow increase in the OD over time as the wheel wears. At some time I would suspect you adjust for the wheel wear (unless you have automated compenastion built in). The question becomes how do you decide when to adjust, and how much do you adjust?
 
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