Gage Ramp;R for Destructive Testing

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    RL Bredeweg

    I could really use some help with this area, we have to respond for corrective action to our Registrar ASAP.What the test is is called is a “weld breakout test” they use a hydraulic press with a gage(Pressure meter) that reads in psi the part is fixtured and a ball on the end of the press comes down and pushes on the weld seam – Minimum specification for fracture is 3,000 Lbs. – No Max spec (infinity) or weld fracture. What I was considering is to verify the accuracy of the gage with a certified LOAD CELL for correlation to the psi meter and than to review the last 30 days of measurement recordings (which I found out were being recorded as pass/fail).



    i’m also doing a project in spot welding parameters (current, pressureand time) optimization.
    For my Gage R&R i also need to do a destructive testing and i understand that MINITAB 13 has a provision for doing Gage R&R for destructive testings.
    The file folder can be located by going in Quality -> Gage R&R -> Nested.
    I’ve not yet tried it but would be doing it soon.



    The test for your product may be destructive, but that doesn’t mean that your gage r&r has to be. Find a way to test the gage that can be repeated (something that can exceed the pressure you need to verify to without losing it’s rebound).


    Andrew Brody

    First, I would verify the accuracy of the gage itself by performing regular calibrations on the gage itself. Possible the appropriate ASTM can help you there. Once you know the gage is accurate, you will have documentation that the readings you are getting are accurate.

    Second, you need to decide if you want to continue with the pass/fail system or switch to an absolute number system. If you choose pass/fail, your documented test instructions (Work Instructions) must contain a statement that a test response of “pass” indicates a reading of 3000 or greater. If this calibration statement is imbedded in the work instruction for the test itself, you will want to include that 3000 is the minimum acceptable reading allowed for a passing test.

    Third, if you wish to change to a numeric system, simply record the readings you get stating that 3000 is your target reading. Give yourself a standard percent variance allowed by the ASTM method and when you fall outside that variance, you will have to recalibrate this piece of equipment plus follow your out of calibration requirements of your quality system. This applies as well for the second paragraph when you translate your readings to pass/fail.

    This is somewhat simplified, so feel free to e-mail me back and I will give you instructions on how to get in touch with me.

    Andy Brody, Quality Systems Manager
    Marcus Paint Co.
    Louisville, KY



    Some UP gave us a seminar about Measurement System Analysis and one of the topic there was Gage Repeatability and Reproducibility (GR&R) According to them GR&R can not be be for distructive measurement since we are conducting an analysis of the error coming from both operator and the instruments itself, if the sample is distroy there cant be no repeated measure and the error coming from the operator can not be measure. For the distructive measurement the linearity study can be use
    This is what they thought us.



    What is a linearity study ?

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