Xact Measure vs legacy mode True Position

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  • Xact Measure vs legacy mode True Position

    Can someone please help me understand the difference between xact an legacy. I really need to be dimensioning our True positions in xact. I just started here a few months ago and this is the way it's always been done and its easier for the operators to understand since tp on legacy mode does not subtract the mmc like xact does in the report. I'm attaching a picture of a dimension with both to try and get some understanding.

    Why is the measured field for the datum .055 under the feature I'm tolerancing is my main question

    I also need to know what fixed means and why my x deviation is 0 in xact measure when it is .065 in legacy?

    What does rotation mean?

    Thanks for your help
    Attached Files

  • #2
    Your alignment is different for the legacy from what xact calculates with just datum A. Also in xact you have MMB on the datum A. Did you incorporate it into legacy? LOL

    Comment


    • dhoughton
      dhoughton commented
      Editing a comment
      The alignment is the same as you can see in legacy, yes I incorporated MMC for datum A in legacy.....

    • Nano Vujkovic
      Nano Vujkovic commented
      Editing a comment
      For datums it's MMB (maximum material boundary), and legacy does't do well with modifiers on datums. In exact you are only aligned to datum A. What is your alignment to measure in legacy mode, i bet its more than just datum A (you probably constrained all 6 DOF's).

  • #3
    I'm extremely confused by this. The legacy position leads me to believe that you're measuring two nominally concentric circles in the Z workplane.

    The xact position shifts and rotations make it look as if the primary datum feature is in the Y workplane.

    Everything about the xact position looks botched to me. And the D1 diameter in the legacy position is OOT, but not flagged as being OOT. In the legacy position, the 24.200 diameter is the primary datum. Is this same diameter defined as the datum A used in the xact position?

    Comment


    • dhoughton
      dhoughton commented
      Editing a comment
      Is this same diameter defined as the datum A used in the xact position?

      Yes, the same 24.2 Diameter is defined as Datum A and the workplane is Z and these are two nominally concentric circles. Datum A is an ID and the feature is an OD

    • vpt.se
      vpt.se commented
      Editing a comment
      This can depend on what is chosen as reporting alignment - "Use current" or "According to datums". I'd make sure I selected "Use current" in order to correlate with legacy.

    • dhoughton
      dhoughton commented
      Editing a comment
      vpt.se

      I changed to use current and nothing changed. Can you tell me why on the second line in xact CIRA has a value of .055?

  • #4
    Seeing the actual code for Datum A, the hole being measured, and the alignment would be helpful.
    PC-DMIS 2016.0 SP8

    Jeff

    Comment


    • dhoughton
      dhoughton commented
      Editing a comment
      CIR_A =FEAT/CONTACT/CIRCLE/DEFAULT,CARTESIAN,IN,LEAST_SQR
      THEO/<0,6.374,0>,<0,-1,0>,24.2
      ACTL/<-0.268,6.374,-1.485>,<0,-1,0>,24.246
      TARG/<0,6.374,0>,<0,-1,0>
      START ANG=0,END ANG=360
      ANGLE VEC=<1,0,0>
      DIRECTION=CCW
      SHOW FEATURE PARAMETERS=NO
      SHOW CONTACT PARAMETERS=NO
      XZ_ALN =ALIGNMENT/START,RECALL:MAN_ALN,LIST=YES
      ALIGNMENT/TRANS,XAXIS,CIR_A
      ALIGNMENT/TRANS,ZAXIS,CIR_A
      ALIGNMENT/END
      PLN_Z =FEAT/CONTACT/PLANE/DEFAULT,CARTESIAN,TRIANGLE,LEAST_SQR
      THEO/<0,0,0>,<0,-1,0>
      ACTL/<-0.004,-0.276,-0.02>,<0.0114583,-0.9995881,0.0263138>
      TARG/<0,0,0>,<0,-1,0>
      ANGLE VEC=<1,0,0>,RADIAL
      SHOW FEATURE PARAMETERS=NO
      SHOW CONTACT PARAMETERS=NO
      DCC_ALN =ALIGNMENT/START,RECALL:XZ_ALN,LIST=YES
      ALIGNMENT/LEVEL,ZPLUS,PLN_Z
      ALIGNMENT/TRANS,ZAXIS,PLN_Z
      ALIGNMENT/TRANS,XAXIS,CIR_A
      ALIGNMENT/TRANS,YAXIS,CIR_A
      ALIGNMENT/END
      MOVE/POINT,NORMAL,<0,30,20>
      MOVE/INCREMENT,<0,100,0>
      TIP/T1A0B0, SHANKIJK=0, 1, 0.027, ANGLE=179.351
      MOVE/POINT,NORMAL,<-15,60,-30>
      CIR_001 =FEAT/CONTACT/CIRCLE/DEFAULT,CARTESIAN,OUT,LEAST_SQR
      THEO/<0,0,-35.64>,<0,0,-1>,20.44,0
      ACTL/<0.062,0.066,-35.64>,<0,0,-1>,20.481,0
      TARG/<0,0,-35.64>,<0,0,-1>
      START ANG=0,END ANG=180
      ANGLE VEC=<-1,0,0>
      DIRECTION=CCW
      SHOW FEATURE PARAMETERS=NO
      SHOW CONTACT PARAMETERS=NO
      CIR_020 =FEAT/CONTACT/CIRCLE/DEFAULT,CARTESIAN,OUT,LEAST_SQR
      THEO/<0,0,-11.47>,<0,0,1>,20.44,0
      ACTL/<0.044,0.062,-11.47>,<0,0,1>,20.488,0
      TARG/<0,0,-11.47>,<0,0,1>
      START ANG=0,END ANG=180
      ANGLE VEC=<1,0,0>
      DIRECTION=CCW
      SHOW FEATURE PARAMETERS=NO
      SHOW CONTACT PARAMETERS=NO
      DIM 002= POSITION OF CIRCLE CIR_001 UNITS=MM ,$
      GRAPH=OFF TEXT=OFF MULT=10.00 OUTPUT=BOTH FIT TO DATUMS=OFF DEV PERPEN CENTERLINE=ON DISPLAY=DIAMETER
      AX MEAS NOMINAL +TOL -TOL BONUS DEV OUTTOL
      X 0.062 0.000 0.062
      Y 0.066 0.000 0.066
      DF 20.481 20.440 0.050 0.050 0.009 0.041 0.000 ---#
      D1 24.246 24.200 0.040 0.040 0.080 CIRCLE CIR_A AT MMC
      TP 0.181 MMC 0.200 0.089 0.181 0.000 --#-
      END OF DIMENSION 002
      DIM 021= POSITION OF CIRCLE CIR_020 UNITS=MM ,$
      GRAPH=OFF TEXT=OFF MULT=10.00 OUTPUT=BOTH FIT TO DATUMS=OFF DEV PERPEN CENTERLINE=ON DISPLAY=DIAMETER
      AX MEAS NOMINAL +TOL -TOL BONUS DEV OUTTOL
      X 0.044 0.000 0.044
      Y 0.062 0.000 0.062
      DF 20.488 20.440 0.050 0.050 0.002 0.048 0.000 ---#
      D1 24.246 24.200 0.040 0.040 0.080 CIRCLE CIR_A AT MMC
      TP 0.153 MMC 0.200 0.082 0.153 0.000 --#-
      END OF DIMENSION 021
      MOVE/POINT,NORMAL,<-15,175,-10>
      DATDEF/FEATURE=CIR_A,A
      FCFLOC1 =POSITION : CIR_001
      FEATCTRLFRAME/SHOWNOMS=YES,SHOWPARAMS=YES,SHOWEXPANDED=YES
      CADGRAPH=OFF,REPORTGRAPH=OFF,TEXT=OFF,MULT=10.00,A RROWDENSITY=100,OUTPUT=BOTH,UNITS=MM
      COMPOSITE=NO,FIT TO DATUMS=YES,DEV PERPEN CENTERLINE=ON,OUTPUT ALIGNMENT=Datum Reference Frame
      CUSTOMIZED DRF=NO
      STANDARDTYPE=ASME_Y14_5
      SIZE TOLERANCES/1,DIAMETER,20.49,0.05,0.05
      PRIMARY DIMENSION/POSITION,DIAMETER,0.2,MMC,A,MMC,<size>,<dat>,<dat>
      SECONDARY DIMENSION/<Dim>,<tol>,<MC>,<dat>,<dat>,<dat>
      NOTE/FCFLOC1
      FEATURES/CIR_001,,
      CIR_001
      X:NOM=0
      Y:NOM=0
      <NEW>
      DATUMS
      D1:NOM=24.2,+TOL=0.04,-TOL=0.04

  • #5
    I have ever seen XactMeasure seem to get confused if you measure a datum or feature in one workplane and then rotate the alignment to another workplane. You measure datum A with it in the Yminus workplane and then level a Yminus plane to Zplus essentially rotating the alignment by 90 degrees. This could be the cause for the error.
    Try leveling PLN_Z to Yminus as it is measured or remeasure CIR_A with a new name after you level to Zplus and using that as the datum. This could make the difference.
    PC-DMIS 2016.0 SP8

    Jeff

    Comment


    • dhoughton
      dhoughton commented
      Editing a comment
      I will give this a try and let you know if this changes anything. Thanks for your help.

  • #6
    Blatantly stealing a picture from Josh Carpenter :

    breakdown of bonus xactmeasure.jpg
    PC-DMIS CAD++ 2o19 R1 SP4

    Comment


    • dhoughton
      dhoughton commented
      Editing a comment
      Thank you so much! This at least helps me understand the report. I really appreciate your help

    • dhoughton
      dhoughton commented
      Editing a comment
      One more question. When this line reports in red but all my diameters are in tolerance. Is this number red because the part is using bonus tolerance to be in spec and without bonus it would be out of spec?

      Thanks

    • vpt.se
      vpt.se commented
      Editing a comment
      That depends on the version (I think). IIIRC, some versions displayed the datums red (wrongly) but was within tolerance.

      I think it's meant to say if the diameters are within, but the datum is out (red) the fitting succeeded but made the datum out of tolerance (the fitting used more bonus than allowed), in other words, the position is OOT. Like I said, I am not 100% on this speculation.

  • #7
    Originally posted by Nano Vujkovic View Post
    For datums it's MMB (maximum material boundary), and legacy does't do well with modifiers on datums. In exact you are only aligned to datum A. What is your alignment to measure in legacy mode, i bet its more than just datum A (you probably constrained all 6 DOF's).
    To say Legacy "doesn't do well with modifiers on datums" is a bit of a not well done description. There is a document somewhere, penned by Rob Jensen IIRC, that explains when you use datum modifiers in Legacy the software then 'switches' from a viable variable data output to a coded Go/NoGo output. That is if it shows you are OOT is NG and if shows you are In Tolerance, then you are but the actual numerical value displayed in either case is not what would be obtained by doing a proper surface plate layout and True Position Calculation. (By proper surface plate layout I mean the incredibly difficult and time consuming process of measuring the datums that material boundary modifiers apply to and using the allowed deviations based on size to 'shift' the Datums to 'best fit' the feature to be reported. The document I refer to above does a much better job of explaining if anyone wants to dig it up and read it. If you have searched and can't find it, PM me, I think I have it in my archives somewhere, but it may be a day or so before I am willing to spend the time to dig it out.

    Also, I wrote a review of the Pc-Dmis Xactemeasure GD&T course I took in 2010 that provides a lot of valuable insight into what Xactmeasure does and why. It has been posted to this forum many times.

    tl:dr Legacy is a very blunt tool for position with MMB applied to datums. If you must use legacy you will get more reliable data by acting as if there are no modifiers on datums. If you must use legacy with modifiers on datums, do the research to know what the output really means.

    HTH & Lot's O' Luck!


    sigpic"Hated by Many, Loved by Few" _ A.B. - Stone brewery

    Comment


    • Nano Vujkovic
      Nano Vujkovic commented
      Editing a comment
      **** Wes, what was the point of your post? Just to tell me how stupid i am? lol

    • EmilySue
      EmilySue commented
      Editing a comment
      That's not his point at all. I'm a year in and most of this is over my head. ;-) But I will remember to come looking for it when I'm ready. Thanks, Wes!

    • JamesMannes
      JamesMannes commented
      Editing a comment
      I believe this is the paper that Wes spoke of....
      https://drive.google.com/open?id=0B9...HVaY1BiWmtzMUE
      ...check it out, and read the whole thing to get the way it all works. This is old but the info is still valid.

  • #8
    Originally posted by Nano Vujkovic View Post
    **** Wes, what was the point of your post? Just to tell me how stupid i am? lol
    No. My purpose was not to tell you how stupid you are. If I had intended to do that, I would have done just that. I honestly have not read enough posts from you to have an opinion about your intelligence or lack thereof, but I can say your epidermis seems to be a bit thin.

    I was attempting to disseminate important information relevant to the topic that no one else had mentioned in the thread prior to my post.

    All that said, feel free to ignore my posts, or even better, put me on 'ignore', not that I post all that often here . . . anymore . . .


    sigpic"Hated by Many, Loved by Few" _ A.B. - Stone brewery

    Comment


    • Nano Vujkovic
      Nano Vujkovic commented
      Editing a comment
      My skin is just fine, thank you. What i said, i said jokingly.
      Either way, we used to talk some 5 years back and you thought me a lot, i figured you might remember me, guess not. But if you want to ignore each other, that's fine too.

    • KIRBSTER269
      KIRBSTER269 commented
      Editing a comment
      "You want this, don't you? The hate is swelling in you now. Take your Jedi weapon. Use it. I am unarmed. Strike me down with it. Give in to your anger. With each passing moment you make yourself more my servant."

  • #9
    Originally posted by Nano Vujkovic View Post
    My skin is just fine, thank you. What i said, i said jokingly.
    Either way, we used to talk some 5 years back and you thought me a lot, i figured you might remember me, guess not. But if you want to ignore each other, that's fine too.
    Now that you mention it, I do remember you . . . vaguely. . . I have slept since then. We use or [sarcasm] tags [/sarcasm] or "JK" (Just Kidding) to indicate as much.

    Happy Friday Eve!
    sigpic"Hated by Many, Loved by Few" _ A.B. - Stone brewery

    Comment


    • Schrocknroll
      Schrocknroll commented
      Editing a comment
      [sarcasm]Would "lol" work?[/sarcasm] Asking for a friend. JK

  • #10
    Originally posted by Schrocknroll View Post
    [sarcasm]Would "lol" work?[/sarcasm] Asking for a friend. JK
    LOL

    sigpic"Hated by Many, Loved by Few" _ A.B. - Stone brewery

    Comment


    • #11
      Originally posted by KIRBSTER269 View Post
      "You want this, don't you? The hate is swelling in you now. Take your Jedi weapon. Use it. I am unarmed. Strike me down with it. Give in to your anger. With each passing moment you make yourself more my servant."
      "Whatever Man. I mean that's just like your opinion."
      sigpic"Hated by Many, Loved by Few" _ A.B. - Stone brewery

      Comment


      • KIRBSTER269
        KIRBSTER269 commented
        Editing a comment
        I was going to attach the clip, but I figured you got the jist of it.

    • #12
      Wes Cisco yes this is the link to that paper that Rob did. Also in Legacy you can select (fit to datums)..

      https://drive.google.com/open?id=0B9...HVaY1BiWmtzMUE
      Time for the Trolls to leave.

      Comment


      • #13
        something...

        I don't see a ROTATE in your alignment.

        XactMeasure will **** the bed unless you have a complete alignment.

        Also, Xact will blow up if you use two circles to rotate to.
        Code:
        ALIGNMENT/ROTATE_CIRCLE,ZPLUS,TO,C_02,AND,C_01,ABOUT,YMINUS
        Even if they're not part of your datum structure.

        Construct a line between the circles, and ROTATE to that.

        [Disclaimer: This all applies to v2011. Newer versions may be different.]
        One screenshot is worth a thousand Need more info
        Never attribute to malice that which is adequately explained by stupidity...

        Comment


        • vpt.se
          vpt.se commented
          Editing a comment
          I use circles to rotate to all the time without issues. Then again, I am not using v2011.

        • AndersI
          AndersI commented
          Editing a comment
          XactMeasure should [in theory] be *totally* independent of your alignment if the datums lock all 6 DOF. If the datums are not a complete lock, the mathematics demand that the missing parts are filled in from somewhere, and here the current alignment comes in...

        • dhoughton
          dhoughton commented
          Editing a comment
          OK....this has all helped me understand xact measure TP.....I thought. Now the report is not subtracting the bonus and giving me a measurement value above the tolerance but not calling it OOT. For example...tolerance is 0.1 / meas = .147 / bonus = .160. [email protected]%^???

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