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GR&R Requirements

Discussion in 'IATF 16949:2016 - Automotive Quality Systems' started by gkoenig, Mar 17, 2016.

  1. gkoenig

    gkoenig New Member

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    Hello,

    I completed a PPAP for a customer part that has several critical characteristics. A GR&R was performed for a 1" micrometer that measures one of these critical dimensions. All other dimensions, including the remaining critical, are measured by an optical system, to which a GR&R was also performed.

    The customer is requiring GR&Rs to be performed for all critical characteristics. It seems to me that this is redundant since the same equipment is being used and a GR&R was already performed. The equipment has recently been calibrated and has been in spec. The equipment does not know the difference between one measurement or another.

    Are separate GR&Rs for each critical dimension necessary or is one GR&R study adequate? I would appreciate any input as I have had a hard time researching an answer.

    gjkoenig
     
  2. Miner

    Miner Moderator Staff Member

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    It depends on the measurements themselves. For example, the ability of the 1' micrometer to measure distances between flat surfaces within a limited range should be virtually identical. However, the ability to measure a diameter may be strikingly different from the flat surfaces. Same with the optical system. Discuss with your customer the possibility of grouping flat surface distances together, diameters together, angles together, etc. You may want to perform a few studies within the same group to provide data to help convince your customer.
     
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  3. ncwalker

    ncwalker Well-Known Member

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    Hi. I am a typical customer. I will echo Miner's sentiment. If you are giving me, say, some sort of shaft with several bearing journals all different (slightly) diameters. And you are going to check them with the same micrometer, because it can, I would be OK with you doing an R&R on the one with the tightest tolerance. Because that makes sense.

    However, if you are then going to use the same micrometer to check a part that is awkward and very unwieldy, I will want another Gage R&R. Why? Because everyone can hold a shaft easily. But an awkward, out of balance part requires a little more care just because it is unwieldy.

    What I am trying to say is it is reasonable to say a gage is OK a priori IF the circumstances of measurement are reasonably similar. The key is understanding if different measurement circumstances will or will not affect the reliability of the gage.

    Here's another example - Go back to the shaft ... if ONE of my journals requires a 2" micrometer, I may be OK with NOT doing a Gage R&R on that. Because a 2" micrometer is similar to a 1" micrometer. But if there is a flywheel on the end of the shaft that requires a 6" micrometer we have a different story. Comparatively, a 6" mike is much larger than a 1" or 2" mike. You can't manipulate a 6" one handed. It's a different situation.

    The perfect world situation is you do everything. In the real world, cost and timing gets in the way. Ergo you need to have reasonable discussion with your customer.
     
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