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Variation

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  • #34142

    ELISEO
    Participant

    I try to get the R&R report according to the SPC book by GM, Ford and Chrysler, in my excell format that I have, but cannot to clarify the two results, %Manufacturing process variation; and % tolerance variation because the first one gives me 86.84% and the second one is 8.51%, I believe the second one is the real but; What does mean the first one percentage?.
    Best regards.

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    #93733

    Manuel Perez Aragon
    Participant

    Estimado Eliseo: lo normal el R&R sea menor si lo relacionas con las tolerancias que si lo relacionas con el proceso de producción. Porque?, porque el proceso debe variar mucho menos que los límites de las tolerancias (debe estar como poco en un 66% de dichas tolerancias). Si Tienes un RR del 86% sobre la variación del proceso eso significa que tu sistema de medición varia casi tanto como tu proceso. Es admisible siempre y cuando tu proceso este bajo control y no tengas valores cercanos a las tolerancias. Si precisas mas detalles, estoy a tu disposición. Manolo Perez Aragon. Auditor ISO/TS 16949

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    #93748

    Arend
    Participant

    Dear Eliseo,Both are ‘real’ values, and both can be important:
    -the% Manufacturing Process Variation is a measure for the repeatability and reproducability, judged against the variation in the process.
    -the% Tolerance Variation is a measure for the repeatability and reproducability, judged against the tolerance (USL-LSL).The first one is important if you want to use the measurement to differentiate between products. Typically this would be if you want to do process improvement work, laboratory tests and so on.
    The second is important if you want to judge the products against the specs. This is typically what you do in production testing.The data that you give show that the measurement is not suitable for testing differences between your products, but it is suitable for fail/pass decisions in production testing.So which of the two outcomes is important for you depends on the purpose of the measurement.I hope this was helpfull!kind regards,
    Arend

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