Surface Profile scans missing points

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  • Surface Profile scans missing points

    I have a relatively complex part with an all over surface profile dimension. I am scanning the part using patch scans and freeform scans. When I run it on the CMM, the part runs through but some of the scans have 0 points after they are done. Any clue what may be happening?

    For example, one patch scan has 9 levels, roughly 200 points per level for a rough total of 1800 points. After execution, there are none.

  • #2
    maybe regenerate or re calculate your points, or maybe show us your settings.
    (In Memory of my Loving wife, "Ronda" who I lost March 7, 2016. I love you baby.)
    They say "Nobody's Perfect." I must be Nobody.

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    • #3
      I did regenerate the points but they still vanish after running.

      Capture.JPG

      Capture.JPG

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      • KIRBSTER269
        KIRBSTER269 commented
        Editing a comment
        check the best fit box, and regenerate not saying that fixes but I myself always do best fit

    • #4
      I have only seen this happen when you have FINDNOMS checked and the points exceed the findnoms tolerance. It will normally ask you if you want to delete the points that exceed the tolerance. Are you seeing either pop-up during execution?
      153010 Global Advantage w/ LSPX1H_T Analog Probe
      7107 Global Classic TP20
      2019R1 SP1 CAD++

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      • JacobCheverie
        JacobCheverie commented
        Editing a comment
        I do not believe that warning would've been put in there but I will give it a check.

      • RIDER
        RIDER commented
        Editing a comment
        Does your 0.095" tolerance exceed your current probe's radius?

      • JacobCheverie
        JacobCheverie commented
        Editing a comment
        Probe radius is about .060" which would leave .035" for form error. The only thing that I can think is I am getting the program ready off a setup piece and the form isn't very good. The profile tolerance is .020 to begin with, so perhaps the form of the setup piece does actually exceed the allowable .035". I have assigned a variable to my findnoms tolerance and will bump it up for now. Once I get the actual part, I will try bringing it back down.

    • #5
      You might also want to check the vectors of the surfaces.
      sigpic
      Originally posted by AndersI
      I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

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      • JacobCheverie
        JacobCheverie commented
        Editing a comment
        Thanks for the suggestion, my vectors are all OK.

      • Matthew D. Hoedeman
        Matthew D. Hoedeman commented
        Editing a comment
        Another thing to check, when I scan (find noms) is to set the scan to ONLY look at the selected surfaces. I work sheet metal, I don't want the scan on a part that is 1mm off and only 0.5mm thick to look at the wrong surface when finding noms.

      • JacobCheverie
        JacobCheverie commented
        Editing a comment
        Good call, thankfully the part is quite bulky so I shouldn't have to worry about PC-DMIS looking at the opposite surfaces.

    • #6
      Hi JacobCheverie , try changing the execution controls from DEFINED to RELEARN. With a defined scan, the probe follows the predefined path that gets sent to the controller. If the part deviates from nominal by a large enough amount, it is possible for the probe to loose contact with the surface but it will continue to follow the pre-defined path and essentially scan fresh air. When this happens it will not return any points. The same thing can happen if scanning at high speed and the probe "bottoms out" - it will throw away points gathered outside of the probe limits.
      Neil Challinor
      PC-DMIS Product Owner

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

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      • JacobCheverie
        JacobCheverie commented
        Editing a comment
        Thanks Neil. Now that you mention it, I did bump up the scan speed quite a bit because I'm just trying to make sure there are no collisions and the program takes a little over an hour. I am using a passive sensor and I set my scan speed to 40 mm/s. I'm sure that's too high for a passive sensor. I'll try dropping it down, re-running the scan, and seeing if the points are kept.

    • #7
      Do not scan on CAD seams. Scans and seams don't get along
      Jesse Krook

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      • JacobCheverie
        JacobCheverie commented
        Editing a comment
        Thanks for the tip. No seam scanning here.

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