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Variable MSA - % GRR for one sided tolerance

Discussion in 'Gage R&R and MSA - Measurement Systems Analysis' started by Englishman Abroad, May 11, 2016.

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  1. Englishman Abroad

    Englishman Abroad Member

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    Hello All,

    How do I calculate the % GRR for a one sided tolerance?

    Typically I have a minimum paint thickness specified by the Customer. I can carry out a variable MSA to find the gauge variation, but I can not express this as a percentage of the tolerance, as the tolerance is only one sided.

    Has anyone found the industry standard relating how to express this - I cannot see in MSA 4th?

    I appreciate your thoughts about the real statistical validity of this, and also I would like your thoughts on how to explain to Customer Quality engineers and auditors who may be less statistically aware!

    (I could imagine some explanation compared to process mean, or guard banding based on 3xsigma of the gauge - But I have a problem explaining that we can not calculate a %).

    Thanks in advance to all.
     
  2. Miner

    Miner Moderator Staff Member

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  3. Englishman Abroad

    Englishman Abroad Member

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    Miner,

    Thanks, I appreciate your explanations of how Minitab calculates the percentages, and also your comments about thinking about what we are trying to express with the %.

    Do you have any experience how to explain to Customers and auditors?

    Thanks
     
  4. Miner

    Miner Moderator Staff Member

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    No. I am no longer in the automotive industry, and developed that line of reasoning after leaving. All of my MSA work now is strictly internal where I am the subject matter expert, and I do not have to justify my analyses to customers or auditors.
     

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