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Xact Measure problem

slesholdofthreep
Has anyone had problems with Xact Measure TP dims? I have various parts with MMC on the DF as well as the Datums. As may be expected the DF and the datums all have different size tolerances. When setting up the dimension I tolerance them correctly, but once created the datum tolerances default to the DF tolerance. I have assigned variables for tolerances with little success. In fact I can type in the correct tolerance right into the dimension in the edit window and.. pfft... it reverts back to the DF tol. I am attempting to use this "improved" method because the hexagoon's say that legacy TP dims don't account for MMC on the datums correctly. WTF!

I am running V4.2mr2, but I have seen this in 4.1 and 4.2mr1.
  • Matt- thats a good one when you have a VC on the DF only. Unfortunately, I have VCs on the datums as well which requires a qausi BF on the datums limited to there individual tolerances. If I had a coding solution for that I would be a much better programmer than I am.

    James- thanks for the tip. On a side note, do you think it reports the deviation for the set when dimensioning a group?

    No I don't believe so.

    James, this is only a problem when you need stats for multiple holes right? I ask because doesn't this method solve for simultaneous requirement Jan mentioned?

    Jan, in light of James' statement could one use PCDMIS silmultaneous evaluation function?
    Can you elaborate?

    If by "simultaneous requirement and/or simultaneous evaluation function", you mean the usage of datums as modifiers, no this is not the same as what I am talking about.

    From the left hand side oof the screen you pick your features to be dimensioned and in the FCF you pick your datums. I am picking multiple features from the feature list on the left hand side and only one statistic is being saved. This is incorrect
  • From the left hand side oof the screen you pick your features to be dimensioned and in the FCF you pick your datums. I am picking multiple features from the feature list on the left hand side and only one statistic is being saved. This is incorrect

    Can't one use this approach if stats are not needed?

    I am referring to using the command Insert | Dimension | Simultaneous Evaluation as it pertains to ASME Y14.5M-1994 5.3.6 pg 92. If each feature was dimensioned seperately wouldn't this allow one to output the correct stats while correctly evaluating a part?
  • Yes, that's exactly what you would use. This becomes very important if you have multiple TP calls with EXACTLY the same datum call. You have to use simultaneous evaluation unless the print states otherwise.

    I was told that PC-DMIS will take all features and tries to find a datum shift that creates a "go" situation for all the holes. If it finds one, it will use that datum shift and report all other features to that datum shift.

    I tried it and, again, in my humble opinion, it seems to work!


    Jan.
  • Jan,

    If one does not need to output stats, is it acceptable to select multiple features to evaluate in a single Xact Measure dim? In other words, will that practice adhere to 5.3.6?
  • Jan,

    If one does not need to output stats, is it acceptable to select multiple features to evaluate in a single Xact Measure dim? In other words, will that practice adhere to 5.3.6?

    Ah, good question!

    I can't say for sure. Only Hexagon can tell you this.

    My gut feel is that if you have simultaneous requirements, you should use the simultaneous evaluation. I think that if you use multiple features and use them in a single Xact Measure dim, all wil be individually evaluated against the DRF (they will all get there own unique datum shift).

    But I have never tried to do this specifically.

    What I DID do is measure points and evaluate all them for surface profile. You will get the MAX and MIN, which is corresponds with the maximum and minimum if you evaluate all individually. However, I never tried this with TP.
  • Guys,

    I think you just taught me something. But, can you delve into the subject a little more?

    Let me start by regurgitating what I think I have just read in ASME y14.5 1994. If I have 6 holes that have a True Position of...

    6X DIA 6mm +0.3 -0.00
    |TP|DIA|0.1M|A|B|C|

    ...I should report this as a pattern? So really I would only have 1 statistic? Interesting, because I have been taught to report these all separately.
  • James,

    I believe your initial approach to reporting TP stats of multiple features is the correct one. The spec states, in so many words, that all conditions must be satisfied concurrently. It says nothing about reporting. Therefore one should report the results in whatever manner is advantageous to the concerned parties.
  • So anyone have any thoughts on the pugnacious behavior of the datum tolerances?
  • So anyone have any thoughts on the pugnacious behavior of the datum tolerances?
    I just got some free time. I'll look
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