True Postion tolerance

[calbritton]

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?

[bw_bob]

I'm assuming the 18.9 dim is not round. you could do 2 lines & construct a mid point.

[calbritton]

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

[bw_bob]

Do you know how to assign variables ???

[calbritton]

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

[bw_bob]

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

[than_357]

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.

[jon_dav_uk]

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

[dwade]

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