Tolerance vs. Study Variation - Choosing the right one

M

Maokun

#1
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?
 
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I

Ingo1966

#2
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.
 
M

Maokun

#3
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?
 
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Miner

Forum Moderator
Leader
Admin
#4
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.
 
M

Maokun

#6
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.
:applause:Thanks, Miner.It used for product control.And I know how to estimate the system now.
 
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