True Postion tolerance

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  • True Postion tolerance

    I have a true postion tolerance for this measurement. It includes max material condition for the feature. The problem is the feature as I have created it is a mid-point. See attached dwg. the true position would end up 2 x the deviation in the X direction. Any suggestions?
    Attached Files

  • #2
    I'm assuming the 18.9 dim is not round. you could do 2 lines & construct a mid point.
    sigpic.....Its called golf because all the other 4 letter words were taken

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    • #3
      I took a hit on each side. I constructed a midpoint with these two points. I cannot apply MMC to the constructed point.

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      • #4
        Do you know how to assign variables ???
        sigpic.....Its called golf because all the other 4 letter words were taken

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        • #5
          I must not. Is that how you add MMC to true position of a point?

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          • #6
            Here is something I did quick, just an example....could get you started.


            DIM DIST2= 2D DISTANCE FROM POINT PNT1 TO POINT PNT2 PERP TO YAXIS, NO_RADIUS UNITS=MM ,$
            GRAPH=OFF TEXT=OFF MULT=5.00 OUTPUT=STATS
            AX NOMINAL +TOL -TOL MEAS DEV OUTTOL
            M 18.900 0.040 0.070 18.900 0.000 0.000 -----#---
            ASSIGN/V1 = IF(DIST2.M.OUTTOL==0.00,ABS(DIST2.M.MEAS-18.94),0.00)
            ASSIGN/V2 = V1+.10
            DIM LOC1= TRUE POSITION OF POINT PNT3 UNITS=MM ,$
            GRAPH=OFF TEXT=OFF MULT=1.00 OUTPUT=BOTH DEV PERPEN CENTERLINE=OFF DISPLAY=DIAMETER
            AX NOMINAL +TOL -TOL BONUS MEAS DEV OUTTOL
            X 0.000 -0.041 -0.041
            TP RFS V2 0.000 0.082 0.000 -----#---
            END OF DIMENSION LOC1
            sigpic.....Its called golf because all the other 4 letter words were taken

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            • #7
              If you're not too concerned on MMC, you can report the TP as "Display as Radius". This will only use the displacement and not the 2x part.

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              • #8
                Another option would be to measure the feature with two points as you mentioned previous. Construct a midpoint from these two points then construct a min circsc external circle through these three points which will automatically capture the 18.9 size.
                As long as you are in the correct alignment, simply select true position, apply MMC, enter 0.1 as the geometric tolerance, set the circle tolerance as the tolerance of your feature (+0.04, -0.07) and pick the correct axis

                I have constructed this with generic features below to give you an idea. Hope this helps

                F1 =GENERIC/POINT,DEPENDENT,RECT,$
                NOM/XYZ,0,0,0,$
                MEAS/XYZ,0,0,0,$
                NOM/IJK,0,0,1,$
                MEAS/IJK,0,0,1
                F2 =GENERIC/POINT,DEPENDENT,RECT,$
                NOM/XYZ,18.9,0,0,$
                MEAS/XYZ,18.9,0,0,$
                NOM/IJK,0,0,1,$
                MEAS/IJK,0,0,1
                PNT1 =FEAT/POINT,RECT
                THEO/9.45,0,0,0,0,1
                ACTL/9.45,0,0,0,0,1
                CONSTR/POINT,MID,F1,F2
                A2 =ALIGNMENT/START,RECALL:STARTUP, LIST= YES
                ALIGNMENT/TRANS,XAXIS,PNT1
                ALIGNMENT/END
                CIR1 =FEAT/CIRCLE,RECT,OUT,MIN_CIRCSC
                THEO/0,0,0,0,0,1,18.9
                ACTL/0,0,0,0,0,1,18.9
                CONSTR/CIRCLE,BF,F1,F2,PNT1,,
                OUTLIER_REMOVAL/OFF,3
                FILTER/OFF,UPR=0
                DIM LOC1= TRUE POSITION OF CIRCLE CIR1 UNITS=IN ,$
                GRAPH=OFF TEXT=OFF MULT=10.00 OUTPUT=BOTH DEV PERPEN CENTERLINE=OFF DISPLAY=DIAMETER
                AX NOMINAL +TOL -TOL BONUS MEAS DEV OUTTOL
                X 0.0000 0.0000 0.0000
                DF 18.9000 0.0400 -0.0700 0.0400 18.9000 0.0000 0.0000 -----#---
                TP MMC 0.1000 0.0400 0.0000 0.0000 #--------
                END OF DIMENSION LOC1
                sigpic

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                • #9
                  My method is similar to the others.



                  SLT_1 =AUTO/VECTOR POINT,SHOWALLPARAMS = YES
                  THEO/-0.2175,-0.215,0.305,1,0,0
                  ACTL/-0.2171,-0.215,0.305,1,0,0
                  TARG/-0.2175,-0.215,0.305,1,0,0
                  THEO_THICKNESS = 0,RECT,SNAP = YES,$
                  AUTO MOVE = NO,DISTANCE = 0.2
                  SLT_2 =AUTO/VECTOR POINT,SHOWALLPARAMS = YES
                  THEO/-0.2175,-0.215,-0.45,1,0,0
                  ACTL/-0.2172,-0.215,-0.45,1,0,0
                  TARG/-0.2175,-0.215,-0.45,1,0,0
                  THEO_THICKNESS = 0,RECT,SNAP = YES,$
                  AUTO MOVE = NO,DISTANCE = 0.2
                  SLT_3 =AUTO/VECTOR POINT,SHOWALLPARAMS = YES
                  THEO/0.2175,-0.215,-0.45,-1,0,0
                  ACTL/0.218,-0.215,-0.45,-1,0,0
                  TARG/0.2175,-0.215,-0.45,-1,0,0
                  THEO_THICKNESS = 0,RECT,SNAP = YES,$
                  AUTO MOVE = NO,DISTANCE = 0.2
                  ASSIGN/SLT_V1 = SLT_3.X-SLT_2.X
                  SLT_CPT1 =FEAT/POINT,RECT
                  THEO/0,-0.215,-0.45,0,-1,0
                  ACTL/0.0004,-0.215,-0.45,-0.0018643,-0.9999954,0.0024068
                  CONSTR/POINT,MID,SLT_2,SLT_3
                  ASSIGN/SLT_V2 = SLT_CPT2.X
                  ASSIGN/SLT_V3 = SLT_CPT2.Y
                  ASSIGN/SLT_V4 = SLT_CPT2.Z
                  F3 =GENERIC/CIRCLE,DEPENDENT,RECT,IN,$
                  NOM/XYZ,0,-0.215,-0.45,$
                  MEAS/XYZ,SLT_V2,SLT_V3,SLT_V4,$
                  NOM/IJK,0,-1,0,$
                  MEAS/IJK,0,-1,0,$
                  DIAMETER/0.435,SLT_V1
                  SLT_4 =AUTO/VECTOR POINT,SHOWALLPARAMS = YES
                  THEO/0.2175,-0.215,0.305,-1,0,0
                  ACTL/0.2182,-0.215,0.305,-1,0,0
                  TARG/0.2175,-0.215,0.305,-1,0,0
                  THEO_THICKNESS = 0,RECT,SNAP = YES,$
                  AUTO MOVE = NO,DISTANCE = 0.2
                  ASSIGN/SLT_V5 = SLT_4.X-SLT_1.X
                  SLT_CPT2 =FEAT/POINT,RECT
                  THEO/0,-0.215,0.305,0,-1,0
                  ACTL/0.0005,-0.215,0.305,-0.0018643,-0.9999954,0.0024068
                  CONSTR/POINT,MID,SLT_1,SLT_4
                  ASSIGN/SLT_V6 = SLT_CPT2.X
                  ASSIGN/SLT_V7 = SLT_CPT2.Y
                  ASSIGN/SLT_V8 = SLT_CPT2.Z
                  F4 =GENERIC/CIRCLE,DEPENDENT,RECT,IN,$
                  NOM/XYZ,0,-0.215,0.305,$
                  MEAS/XYZ,SLT_V6,SLT_V7,SLT_V8,$
                  NOM/IJK,0,-1,0,$
                  MEAS/IJK,0,-1,0,$
                  DIAMETER/0.435,SLT_V5
                  A5 =ALIGNMENT/START,RECALL:A_C_D, LIST= YES
                  ALIGNMENT/TRANS,XAXIS,DAT_B1
                  ALIGNMENT/END
                  COMMENT/REPT,Width and position of .435 wide slot to -B- (2X, bottom then top)
                  DIM DIM_3= TRUE POSITION OF CIRCLE F3 UNITS=IN ,$
                  GRAPH=OFF TEXT=OFF MULT=10.00 OUTPUT=BOTH DEV PERPEN CENTERLINE=OFF DISPLAY=DIAMETER
                  AX MEAS NOMINAL +TOL -TOL BONUS DEV OUTTOL
                  X 0.0000 0.0000 0.0000
                  DF 0.4352 0.4350 0.0050 0.0050 0.0052 0.0002 0.0000 ----#----
                  D1 0.2322 0.2320 0.0005 0.0000 0.0002 CIRCLE DAT_B1 AT MMC
                  TP MMC 0.0000 0.0052 0.0000 0.0000 #--------
                  END OF DIMENSION DIM_3
                  A6 =ALIGNMENT/START,RECALL:A5, LIST= YES
                  ALIGNMENT/TRANS,XAXIS,DAT_B2
                  ALIGNMENT/END
                  DIM DIM_4= TRUE POSITION OF CIRCLE F4 UNITS=IN ,$
                  GRAPH=OFF TEXT=OFF MULT=10.00 OUTPUT=BOTH DEV PERPEN CENTERLINE=OFF DISPLAY=DIAMETER
                  AX MEAS NOMINAL +TOL -TOL BONUS DEV OUTTOL
                  X 0.0006 0.0000 0.0006
                  DF 0.4354 0.4350 0.0050 0.0050 0.0054 0.0004 0.0000 ----#----
                  D1 0.2323 0.2320 0.0005 0.0000 0.0003 CIRCLE DAT_B2 AT MMC
                  TP MMC 0.0000 0.0054 0.0012 0.0000 -#-------
                  END OF DIMENSION DIM_4
                  Xcel & MicroVal Pfx & Global 37mr4 thru 2012mr1sp3
                  Contura Calypso 5.4

                  Lord, keep Your arm around my shoulder and Your hand over my mouth. Amen.

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