Tolerance vs. Study Variation - Choosing the right one

[Maokun]

As we know, %Tolerance =100*R&R/[(USL-LSL)/6], and %Study Variation=100*R&R/TV. If we know the tolerance, we can get two results in a spreadsheet.And my question is Which one should be chosen.On other words, is there any condition to choose the right one?

 

[Ingo1966]

Re: Tolerance vs. Study Variation

Hello

If the Gage is used for Product Control --> % Tolerance
If the Gage is used for Process Control --> % Study Variation

AND acc. AIAG 4th edition:

If your Study Parts do not represent the whole Process Range you can also refer to a surrogate Process Variation as TV or you can also include the requested Pp in your calculation. See Details Page 120-121 AIAG MSA 4.th edition.

 

[Maokun]

Re: Tolerance vs. Study Variation

Thank for you reply.

I'm in trouble now. I have analysed the data with MiniTab. The PV is Very low, I'll choose the % Tolerance as %GR&R as your said. But I found the %Tolerance <30%, % SV>30%. I'm puzzled with the result. Is the system OK?

 

[Miner]

Re: Tolerance vs. Study Variation

For what purpose is your gauge used? As Ingo1966 stated, a gauge may be used for product control (i.e., inspection) or process control (i.e., SPC). In the case of a highly capable process, your gauge may be acceptable for inspection, but unacceptable for process control. If your gauge is only used for inspection, this is acceptable.

 

[Ingo1966]

Re: Tolerance vs. Study Variation

Hello


Thanks MINER !

 

[Maokun]

Re: Tolerance vs. Study Variation

For what purpose is your gauge used? As Ingo1966 stated, a gauge may be used for product control (i.e., inspection) or process control (i.e., SPC). In the case of a highly capable process, your gauge may be acceptable for inspection, but unacceptable for process control. If your gauge is only used for inspection, this is acceptable.

Thanks, Miner.It used for product control.And I know how to estimate the system now.