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Understanding Profile of A Line Report

Looking for clarification on how PC-DMIS reports the profile of a line values.

The part in question is a cylindrically symmetrical curve, with a cross section cutout listed as a profile of a line between point A<->point B. No datum structure on the control frame. Profile limit .060"

When getting a report trying to get a best-fit result, I usually expect the min and max values to be similar, and according to the online help https://docs.hexagonmi.com/pcdmis/2020.2/en/helpcenter/mergedProjects/core/geometric_tolerances/Profile_of_a_Line.htm
Setting min/max should find the smallest tolerance to fit all the points, but it shows -.016" to +.034" range.

The initial line of the report shows that it is only using .050" of the .060" tolerance but also is out of tolerance, not helping my confusion.

Taking the actual points reported and running them with the other softwares we have at our facility, I have more experience in and can get the even split of the deviations (-.023"<->+.019") or an overall lower profile (-.013"<->+.025") with another

So is there a simple answer to the following questions
1) is the profile good at the initial .050" reporting, even though it is listing it .004" over?
2) Is there a obvious reason that the min max in not having all the point inside the tolerance window.







  • Graphing your result may give you more insight.
  • Looking for clarification on how PC-DMIS reports the profile of a line values.

    When getting a report trying to get a best-fit result, I usually expect the min and max values to be similar, and according to the online help https://docs.hexagonmi.com/pcdmis/2020.2/en/helpcenter/mergedProjects/core/geometric_tolerances/Profile_of_a_Line.htm
    Setting min/max should find the smallest tolerance to fit all the points, but it shows -.016" to +.034" range.

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    In your example of a profile of a bowl shape, I WOULD expect to see the MAX and Min be equal in magnitude. But, looking at the numbers on the report, I don't think you have reported that feature correctly for a Line Profile.

    A Line Profile is a 2D evaluation relative to a workplane. Like measuring a profile on a optical comparator. The part needs to be oriented correctly to measure it. The points from your evaluation all lie on the same plane, but it is not in the same orientation as your coordinate system.



    Also, in your reporting, you are evaluating the profile relative to the ZPLUS workplane. So, it is viewing the points from the direction shown in top left view in the picture above. The deviations along the Z axis can't be observed properly by the vector_min_max fitting algorithm.

    You can create a temporary alignment that rotates your current alignment about the Z axis by an offset value, so all the points lie on either the YZ or XZ planes. Then report the profile using either XPLUS, XMINUS, YPLUS, or YMINUS workplane - whichever makes sense for the direction you rotate the alignment.
  • try using a specific Gauss filter with remove outliers option