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PC-DMIS 2021.2 - Possible bug with variable of position evaluation

Aaron Baldauf
Hello

I think I found a bug with the extraction (in a variable) of the z value in a position command.

I have a position of a plane to datum B (also a plane). The nominal distance is 43.64mm.
The measured TP value of the feature is 0.518015 and the measured z-value of the feature is 43.899007.

When extracting the z-value via a variable I get a totally different value of ​43.810238. A difference of approx. 0.09mm

To verify the result of the position feature, I aligned to datum B and evaluated each z-value of the plane.
The worst z-value of the individual points is 43.899024... so nearly identical to the position evaluation.
So the error must be in the extracted value.

I don't have any special characters in the name of the features.
PC-DMIS version is 2021.2 SP8 (Build-Nr. 524).

neil.challinor Don Ruggieri

May I send the routine to one of you guys to investigate?




  • We have the constructed extreme point (added in 2021.2 I think): https://docs.hexagonmi.com/pcdmis/20...reme_Point.htm​

    neil.challinor

    I'm aware that the extreme point is part of the newer version of PC-DMIS.

    I meant that it would be great, to have a similar tool (like the HighPoint.exe before PC-DMIS got the native ability) but to help the user extract axis data.
    The current way of extracting the axis data is way too complicated for the user. The old syntax still gets accepted by PC-DMIS but can give wrong results.
    So a tool like this would be a great benefit. Of course a native solution would be preferred.

    I'm in contact with David (and Don) from your team and he mentioned he will talk to you after both your holidays.
  • In the meantime I also got another response from Hexagon by mail:
    Apologies for the delay in responding I was on holiday last week. I have spoken to Neil and we are going to raise this as a bug. I will keep you posted on how this progresses.

    In the short term if you want to find the highest or lowest point you can use the Construct Point option and there is an Extreme Point method which uses the raw hits to evaluate the max or min point either to the current alignment or a user defined alignment. So in your example after the alignment is created you can construct the extreme point and then report this using the legacy position.

    ​
    ​
    And again my reply:
    Thank you very much for looking into this again and treating this as a bug.

    Regarding the highest and lowest point. I think there was a misunderstanding.

    I only mentioned the extreme points to show that Hexagon used to provide little helper tools (in my example the HighPoint.exe) for stuff that was hard for the user to do.
    As it's very complicated to get to the axis data at the moment, I thought a little helper tool would be great addition until PC-DMIS gets an easier native way.

    To actually use the extreme point method is not a solution as not every datum system is reproducible using a classic alignment.
    Again, this was only to show about what kind of tools I was referring.

    ​
  • Great news regarding this topic.

    I reached out to neil.challinor to get an update about this issue.

    This is Neils response:
    You will be pleased to hear that we’ve already made several changes in response to your query.
    • "Old expression syntax" is not available from the expression builder but is supported if typed in via the edit window or if already present in migrated routines.
    • For Position of a cylinder, the older expression now returns the correct value (worst value) when previously these returned only the start point.
    • For Position of a plane, the older expression now returns the worst values as shown in the FCF rather than the first line of the textual table.
      • All GD&T callouts using the old expression language now return the measurement value in the FCF and are no longer based on the first line of the textual analysis, so this fixes the customer issue.

    • Using the old expression syntax FCFLOC1.TP.MEAS or FCFLOC1.MEAS now return the same value.
    • Geometric Tolerance commands now support the assigning the worst X, Y or Z value on a per segment, per feature basis – for example FCFLOC1.SEGMENT[1].FEATURE[1].X.MEAS.

    These changes are available in PC-DMIS 2022.2 SP7 and will also be in the following builds once they are released…

    PC-DMIS 2023.1 SP7
    PC-DMIS 2023.2 SP3
    PC-DMIS 2024.1 Release
    ​

    Thanks for everyone involved Slight smile
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