Calculating Surface RMS

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  • Calculating Surface RMS

    (Newer PC-DMIS & CMM user)
    I have a bowl shaped part that I am tasked with measuring the Surface RMS. I have done a similar part in the past, but I realize now that the process in which I was calculating it was flawed. Fortunately for me, the error in my method was actually creating a buffer, not creating a false "pass".
    The drawing note specifies the surface shall not deviate from the theoretical surface by more than .002"RMS. One degree of freedom is allowed to calculate the best fit surface RMS, a translation of +/- .010"along the z-axis. The previous part I received Hexagon assistance programming, and what we ended up doing was calculating the RMS without allowing for a best fit translation (similar note on previous part)
    The program exported deviations in Z to a .txt, I would then copy that into an XLSX and calculate the RMS externally, and enter the calculated value as a keyed in dimension.

    Is there a way to translate these points to CAD within PC-DMIS and either: A) report to me the new deviations from nominal after translation, or B) show be how far the points translated to become a "best fit"so I can manually calculate the new deviations from CAD?
    I'm poking around now, would teh solution be somewhere within point cloud alignment?
    Thank you for your help.

  • #2
    What version are you running? I created an example routine on the 2020 R1 homepage that shows how to grab deviations and calculate the RMS for an alignment. You might be able to adapt it to your needs. On the Homepage, click on the Discover tab and then Example Routines and select the Advanced Data Assignment example.
    Neil Challinor
    PC-DMIS Product Owner

    T: +44 870 446 2667 (Hexagon UK office)
    E: [email protected]

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    • #3
      Originally posted by neil.challinor View Post
      What version are you running? I created an example routine on the 2020 R1 homepage that shows how to grab deviations and calculate the RMS for an alignment. You might be able to adapt it to your needs. On the Homepage, click on the Discover tab and then Example Routines and select the Advanced Data Assignment example.
      I am running 2019 R2. I'll check it out; thank you!

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    • #4
      Originally posted by neil-challinor
      You can also download the example here if you don't have access to 2020 R1. It will be available until the end of the month.
      https://sendit.hexagon.com/message/K...4BhfqsiU4a26DX
      I am using 2020R1 on an offline seat (Not sure why the main rig isn't on 2020 yet) but I'm reading through it right now. Thanks again; I'll let you know how it goes!

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