CMM not taking hit at theoretical coordinate

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  • CMM not taking hit at theoretical coordinate

    Why are my measured values of a vector point so far off from my theoretical values? I'm measuring points on a blade airfoil and for example my vector point theo is (X 1, Y 1, Z 1) w/ (I 0, J 1, Z 0) but when my program runs in takes the hit at (.994, .999, 1.001) (0,1,0) The .006 off in the X is a big difference in my world. I don't understand why the probe would hit that far off when it is approaching the part parallel to the Y-axis at the given X & Z coordinates.

  • #2
    Sloppy machine, slack in the drive system. You might see better results with a larger prehit/retract value, give it more time to settle in.
    sigpic
    Originally posted by AndersI
    I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

    Comment


    • #3
      Please post your alignment code and then code for the section of your program that is giving you trouble.

      We'd like to help...but this will be very hard without more info.
      Beep beep beep..

      Comment


      • #4
        Here is my code:

        ALN_PART_THEO_CENTER=ALIGNMENT/START,RECALL:TG37728_TBALL,LIST=YES
        ALIGNMENT/TRANS_OFFSET,XAXIS,2.8661
        ALIGNMENT/TRANS_OFFSET,YAXIS,-0.2178
        ALIGNMENT/TRANS_OFFSET,ZAXIS,4.1724
        ALIGNMENT/ROTATE_OFFSET,0.3,ABOUT,ZPLUS
        ALIGNMENT/END
        MOVE/POINT,NORMAL,<-3,0,10>
        TIP/T1A90B0, SHANKIJK=0.007, 1, 0, ANGLE=-179.9977
        ALIGN_START=LABEL/
        MOVE/POINT,NORMAL,<0,2,5>
        WORKPLANE/YPLUS
        MOVE/POINT,NORMAL,<-.445,2,-0.4>
        DAT_X1 =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
        THEO/<-0.445,0.241,-0.4>,<0,1,0>
        ACTL/<-0.4533,0.2531,-0.4035>,<0.0005148,0.9999997,0.000604>
        TARG/<-0.445,0.241,-0.4>,<0,1,0>
        SNAP=NO
        SHOW FEATURE PARAMETERS=NO
        SHOW CONTACT PARAMETERS=YES
        AVOIDANCE MOVE=BOTH,DISTANCE=0.25
        SHOW HITS=NO
        DAT_X3 =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
        THEO/<0.36,0.202,-0.4>,<0,1,0>
        ACTL/<0.3516,0.2137,-0.4041>,<0.0005148,0.9999997,0.000604>
        TARG/<0.36,0.202,-0.4>,<0,1,0>
        SNAP=NO
        SHOW FEATURE PARAMETERS=NO
        SHOW CONTACT PARAMETERS=YES
        AVOIDANCE MOVE=BOTH,DISTANCE=0.25
        SHOW HITS=NO
        MOVE/POINT,NORMAL,<0.36,2,-0.4>
        MOVE/POINT,NORMAL,<0.36,2,0.3>
        DAT_Z1 =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
        THEO/<0.5984,0,-0.0731>,<0.1000067,-0.0048222,0.9949751>
        ACTL/<0.5903,0.0113,-0.0773>,<0.1008071,-0.005475,0.9948909>
        TARG/<0.5984,0,-0.073>,<0.1000067,-0.0048222,0.9949751>
        SNAP=NO
        SHOW FEATURE PARAMETERS=NO
        SHOW CONTACT PARAMETERS=YES
        AVOIDANCE MOVE=BOTH,DISTANCE=0.25
        SHOW HITS=NO
        MOVE/POINT,NORMAL,<0.36,2,0.3>
        DAT_X2 =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
        THEO/<-0.155,0.5644,1.8605>,<0.2086474,0.9755214,-0.0694565>
        ACTL/<-0.1613,0.575,1.8573>,<0.2090935,0.9754558,-0.0690357>
        TARG/<-0.155,0.5644,1.86>,<0.2086474,0.9755214,-0.0694565>
        SNAP=NO
        SHOW FEATURE PARAMETERS=NO
        SHOW CONTACT PARAMETERS=YES
        AVOIDANCE MOVE=BOTH,DISTANCE=0.25
        SHOW HITS=NO
        MOVE/POINT,NORMAL,<-1,2,1.8605>
        DAT_Y2 =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
        THEO/<-0.5266,0.1719,1.8605>,<-0.9774794,0.2102724,-0.0178762>
        ACTL/<-0.5331,0.1827,1.8573>,<-0.9773851,0.2107859,-0.01696>
        TARG/<-0.5266,0.172,1.86>,<-0.9774794,0.2102724,-0.0178762>
        SNAP=NO
        SHOW FEATURE PARAMETERS=NO
        SHOW CONTACT PARAMETERS=YES
        AVOIDANCE MOVE=BOTH,DISTANCE=0.25
        SHOW HITS=NO
        MOVE/POINT,NORMAL,<-1.5,0.1,1.8605>
        MOVE/POINT,NORMAL,<-1.5,0.1,-0.34>
        DAT_Y1 =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
        THEO/<-0.6621,-0.1,-0.34>,<-0.9961947,-0.000926,0.0871508>
        ACTL/<-0.6705,-0.0878,-0.3432>,<-0.9961244,-0.0004663,0.0879545>
        TARG/<-0.6621,-0.1,-0.34>,<-0.9961947,-0.000926,0.0871508>
        SNAP=NO
        SHOW FEATURE PARAMETERS=NO
        SHOW CONTACT PARAMETERS=YES
        AVOIDANCE MOVE=BOTH,DISTANCE=1
        SHOW HITS=NO
        MOVE/POINT,NORMAL,<-1.5,0.1,-0.34>
        MOVE/POINT,NORMAL,<-1.5,0.1,5>
        MOVE/POINT,NORMAL,<0,2,5>
        DCC_PART_ALIGN=ALIGNMENT/START,RECALL:ALN_PART_THEO_CENTER,LIST=YES
        ALIGNMENT/ITERATE
        PNT TARGET RAD=0.002,START LABEL=,FIXTURE TOL=0,ERROR LABEL=ALIGN_FAILED
        MEAS ALL FEAT=ALWAYS,MAX ITERATIONS=4,LEVEL AXIS=YAXIS,ROTATE AXIS=XAXIS,ORIGIN AXIS=ZAXIS
        LEVEL=DAT_X1,DAT_X3,DAT_X2,,
        ROTATE=DAT_Y1,DAT_Y2,,
        ORIGIN=DAT_Z1,,
        ALIGNMENT/END
        GOTO/ALIGN_PASSED

        Comment


        • #5
          The X is a known value at all of the points except DAT_Y1 & DAT_Y2 so I need the machine to hit there. The Z is known for all points except Dat_Z1 and the Y for all except DAT_Y1 and Dat_Y2

          Comment


          • #6
            JABrown,

            The ACTL numbers shown are based their position relative to your previous alignment (ALN_PART_THEO_CENTER). From all of the blades and vanes I've inspected, an iterative alignment of the airfoil target points to the stacking axis is the correct way to go. The iterative alignment will repeat until it places all of the points within the target radius of .002. If you put a location dimension below your alignment your points should be very close to nominal. For aero and IGT blades/vanes I have always had good luck with a target radius of .010 and never saw any benefit going tighter than that.

            Comment


            • #7
              if you are talking about the results from an iterative alignment, yeah, you won't see exact values for the non-locating axis.
              sigpic
              Originally posted by AndersI
              I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

              Comment


              • #8
                Under Parameter Settings (F10), Probe options, look for positioning accuracy. This is how close to the target point the machine must come to call the move complete and move on. A lower number may cause a bit of cycle time increase, a really low number WILL cause cycle time increase.

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