Alignment features

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  • Alignment features


    The question may look quite easy, but i'm using the CMM something like only 4 or 8 hour a month, difficult to learn quickly :/

    I would like to know: the features used to create the DCC alignment inevitably have to be re-measured after the alignment ?
    Till now, the few programs i did works well without doing such a thing, but some colleagues say i should have to, but i can't understand why. Or maybe only in some cases ?
    I remember the trainer told us to not use the features of the manual alignment during the level1 training but can't remember something about not using the DCC features...

    However, yesterday, i had issues when measuring an angularity, i'm using a line created for the alignment as datum B, and noticed that if i just re-measure that same line AFTER the alignment the results are different !

    I have to understand how it works before continuing.

  • #2
    Cosine error / Probe comp error. Google away.
    Last edited by Kp61dude!; 06-10-2017, 05:00 PM.
    PcDmis 2015.1 SP10 CAD++
    Global 7-10-7 DC800S


    • #3
      Pab, it's always best to use both a manual and DCC alignment. Whenever I use 3-2-1 alignments, I use quick align and it automatically sets up a manual and DCC. When I don't, then I pickup features and set it as a DCC.


      • #4
        There are times when the features measured in DCC mode that are used for the first DCC alignment can be dimensioned without issue, but there are times it may not be OK. If you don't have a properly leveled alignment and measure a 2D feature like a circle or line, there can be an error in size, form, and/or location. If you have a tight tolerance dimension it never hurts to remeasure a feature after the alignment to be safe.

        Once you get enough experience you can learn when the first measurement is enough, but sometimes in the beginning it's better to be safe than sorry.
        PC-DMIS 2016.0 SP8



        • #5
          Some programmers use a 2nd DCC alignment whit the "readpoint" technique (they ask the operators to position the probe in a hole for example) then let the machine go in DCC to make the alignments.
          If you lock all 6 DOF in your manual you should be Ok with one DCC.
          sigpicIt's corona time!
          737 Xcel Cad++ v2009MR1....SE HABLA ESPAƑOL


          • #6
            OK; it seems there are no really rules about that. For me that's a bit disturbing to see the machine doing the 2 same measure in just few seconds..., that breaks the program flow !

            I use this little 3D print jig to check 5 parts, and make the manual alignment on it. Then DCC alignment on the part.


            Here is the full program (link), as you can see the CER_EXT and CER2 are measured 2 times, cause they are used to create a line for the rotation.
            The program seems consistent to you ?



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