Profile of a Surface - No Datum vs Flatness

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  • Profile of a Surface - No Datum vs Flatness

    I have a print calling out Profile of a Surface with no Datum on a plane). I have always considered this basically a Flatness callout. I noticed today that the Profile and the Flatness dimension have different results. Looking into it more, the profile of a surface results change based on my current alignment. I have profile on FORMONLY and do not pick up a Datum. Is this is problem in PC-DMIS or am I doing something wrong?


    A7 =ALIGNMENT/START,RECALL:A5,LIST=YES
    ALIGNMENT/LEVEL,ZPLUS,PLN2
    ALIGNMENT/TRANS,ZAXIS,PLN2
    ALIGNMENT/END
    COMMENT/OPER,NO,FULL SCREEN=NO,AUTO-CONTINUE=NO,

    Profile of Surface (No Datum)

    DIM PROF1= PROFILE OF SURFACE OF PLANE PLN2 FORMONLY LEAST_SQR UNITS=IN ,$
    GRAPH=OFF TEXT=OFF MULT=10.00 ARROWDENSITY=100 OUTPUT=BOTH
    AX MEAS MAX MIN
    M 0.0105 0.0056 -0.0049 -------->

    RECALL/ALIGNMENT,INTERNAL,A5

    COMMENT/OPER,NO,FULL SCREEN=NO,AUTO-CONTINUE=NO,

    Profile of same surface in different Alignment. (Still no Datum)

    DIM PROF3= PROFILE OF SURFACE OF PLANE PLN2 FORMONLY LEAST_SQR UNITS=IN ,$
    GRAPH=OFF TEXT=OFF MULT=10.00 ARROWDENSITY=100 OUTPUT=BOTH
    AX MEAS MAX MIN
    M 0.0156 0.0108 -0.0048 -------->
    COMMENT/OPER,NO,FULL SCREEN=NO,AUTO-CONTINUE=NO,

    Flatness of Same surface

    DIM FLAT1= FLATNESS OF PLANE PLN2 UNITS=IN ,$
    GRAPH=OFF TEXT=OFF MULT=10.00 ARROWDENSITY=100 OUTPUT=BOTH
    AX MEAS MAX MIN
    M 0.0105 0.0056 -0.0049 -------->

  • #2
    Yes, I agree with you. Since the profile does not reference datums, then the profile of the surface would essentially be flatness.
    153010 Global Advantage w/ LSPX1H_T Analog Probe
    7107 Global Classic TP20
    2019R1 SP1 CAD++

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    • #3
      Maybe V2014 is not the best version in the past...
      I agree, form only shouldn't be different from an alignment to another, but I think that Least suare form only has no reason to be equal to flatness.
      The flatness should use Chebychev algo, LS uses Gaussian one.

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