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Gage R&R – An Interview With Mario Scalzo

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  • Indium Corporation
  • You may know Mario from his “Tech Support Blog” on our web site. Today we chatted about the importance of gage R&R.

    Jim: We know measurements are only as good as the equipment you use to obtain them. How should our customers insure the integrity of their measurement equipment?
    Mario: Through internal calibration by Quality, external calibration by an accredited lab or by the [equipment] manufacturer, testing against a material of “known” properties, and yearly confirmation by an outside lab. Also, many equipment manufacturers offer a calibration program, like a Service Contract for your automobile.

    Jim: Is there a set procedure for gage R&R, is there a standard that should be referenced?
    Mario: GR&R is a test of your measurement system “drift” if you can think of it like that. This is done by measuring the SAME part, or set of parts, over and over again. There is no “set” procedure, but the more measurements, the more accurate the gage. Also, there are 2 types of gage, to test the equipment and to test the process. By having the same person measure and re-measure over and over, you are testing the machine. By having 2 or more people measure the same part, you can test the reproducibility of the process.

    Jim: I cringe when I see expensive equipment misused, what percentage of paste inspection systems do you estimate are properly verified?
    Mario: I know what we have gone through with our own paste inspection machine, and they are pretty accurate right out of the box, and are usually set-up by the manufacturer. The problem lies with the way it’s used. Paste inspection is designed to be used to maintain control of the process. Which means that within the natural variation, some piece will “fall out”, or not pass inspection. The way that they are being used is completely different. Paste inspection is an expensive waste if:
    • The process is out of control.
    • The inspection limits are set too wide, commonly to allow increased through-put
    • Nothing fails
    • Is being used as a “gate” (Data not tracked)

    From what I have seen, very few companies are using it properly.