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Gage RR % of contribution

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  • #41187

    michel
    Participant

    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 advance

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    #128881

    Summerfield
    Participant

    As per the AIAG Standards (Automotive industry action group) your Gage R&R % contribution value should be =5 for accepting Gage R&R.

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    #128889

    CT
    Participant

    What 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)
    CT

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    #128903

    Doc
    Participant

    Careful 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.

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    #128904

    Sweta / Mintu
    Participant

    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
     

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    #128905

    Doc
    Participant

    I’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.

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    #128915

    CT
    Participant
    #128916

    CT
    Participant
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