Gage RR % of contribution
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CT.
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October 26, 2005 at 11:30 am #41187
Can someone tell me where do the following specs for the Gage R&R % of contribution: less than 2% = good, more than 8% = unacceptable come from ?
Thanks in advance0October 26, 2005 at 12:08 pm #128881As per the AIAG Standards (Automotive industry action group) your Gage R&R % contribution value should be =5 for accepting Gage R&R.
0October 26, 2005 at 2:13 pm #128889What Ash said, assuming Normal Distribution with 99% of area under normal curve or 5.15 standard deviations. Also recall that %Contribution is a ratio of the Variances, so you would want this % to be as low as possible. Were as P/TV is the ratio of the measurement system standard deviation to the total observed standard deviation and thus this % can be higher (less than 30% considered ok)
CT0October 26, 2005 at 3:37 pm #128903Careful here … you are mixing up on the indices.
The AIAG MSA Reference Manual uses the following accpetance criteria for %GRR and %Tolerance. Note that these are standard deviation-based metrics:
<10% – generally acceptable
10%-30% – may be acceptable based upon importance of application, cost of measurement device, cost of repairs, etc.
>30% – not acceptable
Use %GRR when the measurement will be used for process control situations (SPC, process capaiblity, and process improvement)
Use %Tolerance when the measurement will be compared to a specification (inspection or end-of-line comparison to specs).
For a capable process (where Pp>1) the %Tolerance will always be smaller than the %GRR, since the Tolerance width is larger than the 6sigma width. Note that AIAG MSA 3rd Edition now uses 6.00 as the multiplier rather than the old 5.15.
The %Contribution, on the other hand, is a variance-based metric.
AIAG does not specify acceptance criteria for %Contribution. It is usually used to provide an understanding of the respective sources of variation. If %GRR or %Tolerance are too high, you can use %Contribution to determine if the problem is with the operators or the gage itself.
Regardless, %Contribution is actually the square of the respective %StudyVar. So to convert the standard deviation-based acceptance criteria for use with %Contribution we take the square of the cutoffs:
<1% – generally acceptable (.10^2 = .01)
1%-9% – may be acceptable based upon importance of application, cost of measurement device, cost of repairs, etc.
>9% – not acceptable (.30^2 = .09)
Again, these squared metrics are ONLY for %Contribution.0October 26, 2005 at 4:14 pm #128904
Sweta / MintuParticipant@PraveenInclude @Praveen in your post and this person will
be notified via email.Hi! None has responded Michel’s question. AIAG guidelines are fine and are well estalished. Where did Mikel get GRR % 8 not accetable has been determined. Michel please send reference document, if any
Praveen
0October 26, 2005 at 4:45 pm #128905I’m not sure where he got 2% and 8%.
I suspect these are mutated acceptance criteria taken from the 10%^2=1% and 30%^2=9% metrics I mentioned in the earlier post. These are calculated using the AIAG MSA Reference Manual acceptance criteria for %GRR and %Tolerance.
Some people have rounded the 9% up to 10% for ease-of-use/presentaiton.0October 26, 2005 at 6:09 pm #128915Page 19 of this PDF Link list the AIAG Standards for GAGE R&R
http://http://www.minitab.com.mx/training/TrainingSampleMeasurementSystems.pdf#search=’Gage%20R%26R%20%25Contribution’
CT0October 26, 2005 at 6:11 pm #128916http://www.minitab.com.mx/training/TrainingSampleMeasurementSystems.pdf#search=’Gage%20R%26R%20%25Contribution
Maybe this one will work, if not cut and paste
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