account for height tolerance when checking a profile form and location?

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  • account for height tolerance when checking a profile form and location?

    Q
    Last edited by nitpicker; 09-09-2019, 11:11 PM.

  • #2
    It's impossible to have a profile tolerance of 0.003" to a datum if the surface that is rippled has a tolerance of 0.040" to the same datum. Are you sure there are datums on the ripple tolerance?
    AndersI
    SW support - Hexagon Metrology Nordic AB

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    • #3
      This wouldn't happen to be something called a Meter Body, for Honeywell ACS, would it? lol.
      What's the callout on the drawing? From my recollection, -if it is a meter body and the print hasn't changed in 12 years- the profile to 0.003 was not datum dependent, it was form-only profile. I measured it with 3 scan lines using a touchprobe (we didn't have scanning probes back in early 2000's) all the way across the whole convoluted/rippled surface per CAD, then did a best-fit alignment prior to measuring the profile.

      Either way, you need to measure it in accordance with what is defined on the drawing. no improvising.

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      • #4
        I think what you are trying to do is maintain 0.003 form only, for the ripple, and 0.040" to datums, correct?
        You'll want to remove the datums from the FCF on the 0.003" tolerance if you want a composite
        [Profile of surface][0.040][A][B]
        [ one symbol ][0.003][no datums defined]

        In my opinion the figure you link, the 55.4-54.8 should be basic.
        Otherwise, B datum should be removed from the FCF.
        If the 0.040" tolerance is defined on the print like this figure, then they need to either make it BASIC and composite the profile as you are pursuing, or toss B from FCF.
        Last edited by louisd; 09-04-2019, 12:33 PM.

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        • #5
          It would be totally logical if they called out for target points on the funky surface to fall within ±0.020 linear but the form of the geometry unto itself to be within 0.003

          I would suggest:

          1) on the blueprint...calling out three target points on your funky surface. XYZ locations driven from other datums on the print
          2) on PCD.. Iterative align to that surface via those points. also create a plane out of those three points. Tolerance the height of the plane ±0.010 to not only report it but to find where the geometry is. then create a z origin once found & scan and report form only profile to be within 0.003

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          • #6
            Originally posted by nitpicker
            thank you i knew i wasn't going crazy
            The two things are not necessarily mutually exclusive, you know...

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            • DAN_M
              DAN_M commented
              Editing a comment
              If he does go crazy at least it will be a short trip =P

          • #7
            Originally posted by nitpicker
            https://res.cloudinary.com/engineeri...ile_xsndeo.jpg

            no I'm not improvising. im in discussion right now with the engineers about it. I would go to cmm and try my idea, but guy is here calibrating it. I think he will be here all day. that was a picture I found with quick google search of profile with height tolerance. notice the .2 profile tolerance is way smaller than the height tolerance.
            It means 3D angularity of that surface to AB must not exceed .20, and that tolerance band must be within 55.4 - 54.8 dimension.

            In other words, the difference between the lowest and the highest point of 55.4 – 55.8 dimension when taken from AB and not the width, should not exceed .20
            Last edited by DungT; 09-05-2019, 11:23 AM.

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            • #8
              Hopefully this photo loaded. This explains my situation perfectly. How do I put this into pc dmis for form and location and get account for the from datum a height tolerance. Anything outside the .16 profile band is reported bad but drawing shows +/- .5?
              Attached Files

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              • #9
                I believe this would work. Create a point at the origin of the alignment. Do a best fit to the points on the top surface, translating Z only, no rotations. Then create another origin point at the new alignment. Check the Z height of the first origin point in the new alignment.

                This should work if the points from the top surface are created with a CAD model.
                PC-DMIS 2016.0 SP8

                Jeff

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