Iterative alignment question

[Marken199]

I am trying to create an alignment to an airfoil using a six point nest. I have been supplied with the XYZijk of all six points. I can reputably locate this part in a fixture on the CMM.
I set the fixture up and save the alignment for recall into my program.
I start my program out by recalling external alignment. I know where the part coordinate system should be relative to the fixture, so I make the shift for external alignment.
I go to DCC mode and do a my six AutoVector points.
I'm not sure if an iterative alignment is the correct way to go about aligning to these six points. After measuring the six points, I go to Iterative ALignment.
I pick the three points that are on the face of the airfoil. Then two points on the leading edge of airfoil, and one point on a platform for Z.
I use a fixture tolerance of .0002 (inches). Measure ALL always max iterations=6. When I run the program it cycles through the six points 2 times and comes up with a window (see below ) saying there are deviations up to .023inch. Not sure why it would not rehit those points again. I figured I would rehit those 6 points after this alignment and they actually showed on devations up to .0015.
I am a PCDMIS noob ( 3 months ).. Hope I made sense. Thanks
iterpic.jpg

PART NAME  : mddt5612
REV NUMBER :
SER NUMBER :
STATS COUNT : 1

STARTUP    =ALIGNMENT/START,RECALL:USE_PART_SETUP,LIST=YES
            ALIGNMENT/END
            MODE/MANUAL
            FORMAT/TEXT,OPTIONS, ,HEADINGS,SYMBOLS, ;NOM,TOL,MEAS,DEV,OUTTOL, ,
            TEMPCOMP/METHOD = AUTOMATIC,MATERIAL = Zerodur; Nexcera,CTE=0
              ,SET WARNING LIMIT = TRUE,MINIMUM = 18,MAXIMUM = 22
              ,PART SENSOR NUM=DEFAULT,X SCALE= 20,Y SCALE= 20,Z SCALE= 20,PART TEMP=25.1017
            LOADPROBE/STAR_2MM
            TIP/TIP4, SHANKIJK=-0.5378, 0.8431, 0, ANGLE=-90
            RECALL/ALIGNMENT,EXTERNAL,LEFT_MDD
A1         =ALIGNMENT/START,RECALL:LEFT_MDD,LIST=YES
              ALIGNMENT/TRANS_OFFSET,XAXIS,-0.658
              ALIGNMENT/TRANS_OFFSET,YAXIS,-0.2
              ALIGNMENT/TRANS_OFFSET,ZAXIS,-5.4279
            ALIGNMENT/END
A2         =ALIGNMENT/START,RECALL:A1,LIST=YES
              ALIGNMENT/ROTATE_OFFSET,-32.5333,ABOUT,ZPLUS
            ALIGNMENT/END
            MODE/DCC
PNT1B      =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
            THEO/<0.1945,0.1533,6.732>,<-0.3626097,0.8887237,-0.2805075>
            ACTL/<0.2255,0.1463,6.7528>,<-0.3849318,0.8792587,-0.2805917>
            TARG/<0.1945,0.1533,6.732>,<-0.3626097,0.8887237,-0.2805075>
            SNAP=NO
            SHOW FEATURE PARAMETERS=NO
            SHOW CONTACT PARAMETERS=NO
PNT2B      =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
            THEO/<-0.1728,-0.1351,6.732>,<-0.8336443,0.5463291,0.0810043>
            ACTL/<-0.1353,-0.1502,6.7577>,<-0.8446707,0.528159,0.0870598>
            TARG/<-0.1728,-0.1351,6.732>,<-0.8336443,0.5463291,0.0810043>
            SNAP=NO
            SHOW FEATURE PARAMETERS=NO
            SHOW CONTACT PARAMETERS=NO
PNT3B      =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
            THEO/<-0.0343,0.0526,7.245>,<-0.7347837,0.675285,-0.0638986>
            ACTL/<0.0041,0.0428,7.2685>,<-0.7501282,0.6586222,-0.0593676>
            TARG/<-0.0343,0.0526,7.245>,<-0.7347837,0.675285,-0.0638986>
            SNAP=NO
            SHOW FEATURE PARAMETERS=NO
            SHOW CONTACT PARAMETERS=NO
PNT5B      =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
            THEO/<-0.1962,-0.1852,6.732>,<-0.7339043,-0.678704,0.0273002>
            ACTL/<-0.1576,-0.2008,6.7582>,<-0.7184164,-0.6946013,0.0375084>
            TARG/<-0.1962,-0.1852,6.732>,<-0.7339043,-0.678704,0.0273002>
            SNAP=NO
            SHOW FEATURE PARAMETERS=NO
            SHOW CONTACT PARAMETERS=NO
PNT6B      =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
            THEO/<-0.1791,-0.184,7.245>,<-0.6461089,-0.7629105,0.0226003>
            ACTL/<-0.1354,-0.1969,7.2709>,<-0.6288323,-0.7768705,0.0322826>
            TARG/<-0.1791,-0.184,7.245>,<-0.6461089,-0.7629105,0.0226003>
            SNAP=NO
            SHOW FEATURE PARAMETERS=NO
            SHOW CONTACT PARAMETERS=NO
PNT7B      =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
            THEO/<-0.216,-0.069,6.6161>,<-0.0137005,-0.0119004,0.9998353>
            ACTL/<-0.1811,-0.0856,6.642>,<-0.003506,-0.0077766,0.9999636>
            TARG/<-0.216,-0.069,6.6161>,<-0.0137005,-0.0119004,0.9998353>
            SNAP=NO
            SHOW FEATURE PARAMETERS=NO
            SHOW CONTACT PARAMETERS=NO
A5         =ALIGNMENT/START,RECALL:A2,LIST=YES
              ALIGNMENT/ITERATE
                PNT TARGET RAD=0.07,START LABEL=,FIXTURE TOL=0.0002,ERROR LABEL=
                MEAS ALL FEAT=ALWAYS,MAX ITERATIONS=10,LEVEL AXIS=XAXIS,ROTATE AXIS=YAXIS,ORIGIN AXIS=ZAXIS
              LEVEL=PNT1B,PNT2B,PNT3B,,
              ROTATE=PNT5B,PNT6B,,
              ORIGIN=PNT7B,,
            ALIGNMENT/END
PNT1C      =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
            THEO/<0.1945,0.1533,6.732>,<-0.3626097,0.8887237,-0.2805075>
            ACTL/<0.1945,0.1531,6.7321>,<-0.3626097,0.8887237,-0.2805075>
            TARG/<0.1945,0.1533,6.732>,<-0.3626097,0.8887237,-0.2805075>
            SNAP=NO
            SHOW FEATURE PARAMETERS=NO
            SHOW CONTACT PARAMETERS=NO
PNT2C      =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
            THEO/<-0.1728,-0.1351,6.732>,<-0.8336443,0.5463291,0.0810043>
            ACTL/<-0.1738,-0.1354,6.7313>,<-0.8336443,0.5463291,0.0810043>
            TARG/<-0.1728,-0.1351,6.732>,<-0.8336443,0.5463291,0.0810043>
            SNAP=NO
            SHOW FEATURE PARAMETERS=NO
            SHOW CONTACT PARAMETERS=NO
PNT3C      =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
            THEO/<-0.0343,0.0526,7.245>,<-0.7347837,0.675285,-0.0638986>
            ACTL/<-0.0355,0.0529,7.244>,<-0.7347837,0.675285,-0.0638986>
            TARG/<-0.0343,0.0526,7.245>,<-0.7347837,0.675285,-0.0638986>
            SNAP=NO
            SHOW FEATURE PARAMETERS=NO
            SHOW CONTACT PARAMETERS=NO
PNT5C      =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
            THEO/<-0.1962,-0.1852,6.732>,<-0.7339043,-0.678704,0.0273002>
            ACTL/<-0.1975,-0.1859,6.7316>,<-0.7339043,-0.678704,0.0273002>
            TARG/<-0.1962,-0.1852,6.732>,<-0.7339043,-0.678704,0.0273002>
            SNAP=NO
            SHOW FEATURE PARAMETERS=NO
            SHOW CONTACT PARAMETERS=NO
PNT6C      =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
            THEO/<-0.1791,-0.184,7.245>,<-0.6461089,-0.7629105,0.0226003>
            ACTL/<-0.1804,-0.1848,7.2448>,<-0.6461089,-0.7629105,0.0226003>
            TARG/<-0.1791,-0.184,7.245>,<-0.6461089,-0.7629105,0.0226003>
            SNAP=NO
            SHOW FEATURE PARAMETERS=NO
            SHOW CONTACT PARAMETERS=NO
PNT7C      =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
            THEO/<-0.216,-0.069,6.6161>,<-0.0137005,-0.0119004,0.9998353>
            ACTL/<-0.2163,-0.0691,6.6161>,<-0.0137005,-0.0119004,0.9998353>
            TARG/<-0.216,-0.069,6.6161>,<-0.0137005,-0.0119004,0.9998353>
            SNAP=NO
            SHOW FEATURE PARAMETERS=NO
            SHOW CONTACT PARAMETERS=NO
DIM LOC1= LOCATION OF POINT PNT1C  UNITS=IN ,$
GRAPH=OFF  TEXT=OFF  MULT=10.00  OUTPUT=BOTH  HALF ANGLE=NO
AX    NOMINAL       +TOL       -TOL       MEAS        DEV     OUTTOL
X       0.1945     0.0020     0.0020     0.1945     0.0000     0.0000 ----#----
Y       0.1533     0.0020     0.0020     0.1531    -0.0002     0.0000 ----#----
Z       6.7320     0.0020     0.0020     6.7321     0.0001     0.0000 ----#----
T       0.0000     0.0020     0.0020    -0.0002    -0.0002     0.0000 ----#----
END OF DIMENSION LOC1
DIM LOC2= LOCATION OF POINT PNT2C  UNITS=IN ,$
GRAPH=OFF  TEXT=OFF  MULT=10.00  OUTPUT=BOTH  HALF ANGLE=NO
AX    NOMINAL       +TOL       -TOL       MEAS        DEV     OUTTOL
X      -0.1728     0.0020     0.0020    -0.1738    -0.0010     0.0000 --#------
Y      -0.1351     0.0020     0.0020    -0.1354    -0.0003     0.0000 ---#-----
Z       6.7320     0.0020     0.0020     6.7313    -0.0007     0.0000 --#------
T       0.0000     0.0020     0.0020     0.0006     0.0006     0.0000 -----#---
END OF DIMENSION LOC2
DIM LOC3= LOCATION OF POINT PNT3C  UNITS=IN ,$
GRAPH=OFF  TEXT=OFF  MULT=10.00  OUTPUT=BOTH  HALF ANGLE=NO
AX    NOMINAL       +TOL       -TOL       MEAS        DEV     OUTTOL
X      -0.0343     0.0020     0.0020    -0.0355    -0.0012     0.0000 -#-------
Y       0.0526     0.0020     0.0020     0.0529     0.0003     0.0000 -----#---
Z       7.2450     0.0020     0.0020     7.2440    -0.0010     0.0000 --#------
T       0.0000     0.0020     0.0020     0.0011     0.0011     0.0000 -------#-
END OF DIMENSION LOC3
DIM LOC4= LOCATION OF POINT PNT5C  UNITS=IN ,$
GRAPH=OFF  TEXT=OFF  MULT=10.00  OUTPUT=BOTH  HALF ANGLE=NO
AX    NOMINAL       +TOL       -TOL       MEAS        DEV     OUTTOL
X      -0.1962     0.0020     0.0020    -0.1975    -0.0013     0.0000 -#-------
Y      -0.1852     0.0020     0.0020    -0.1859    -0.0007     0.0000 --#------
Z       6.7320     0.0020     0.0020     6.7316    -0.0004     0.0000 ---#-----
T       0.0000     0.0020     0.0020     0.0015     0.0015     0.0000 -------#-
END OF DIMENSION LOC4
DIM LOC5= LOCATION OF POINT PNT6C  UNITS=IN ,$
GRAPH=OFF  TEXT=OFF  MULT=10.00  OUTPUT=BOTH  HALF ANGLE=NO
AX    NOMINAL       +TOL       -TOL       MEAS        DEV     OUTTOL
X      -0.1791     0.0020     0.0020    -0.1804    -0.0013     0.0000 -#-------
Y      -0.1840     0.0020     0.0020    -0.1848    -0.0008     0.0000 --#------
Z       7.2450     0.0020     0.0020     7.2448    -0.0002     0.0000 ----#----
T       0.0000     0.0020     0.0020     0.0015     0.0015     0.0000 -------#-
END OF DIMENSION LOC5

[Schlag]

I think it exceeded your TOL by so far it knows it cannot solve ? Increase the TOL and run it and see if it make sit thru.

[AndersI]

What's your "Point Target Radius"? That's what will decide if the iteration should stop or retry. The "Fixture Tolerance" doesn't come into play until you have more than six points (if I have understood it correctly).

[Marken199]

The point target tolerance is .070. Maybe the initial points are out that much. I will increase the target tolerance and try again later today. Thanks for the help Anders and Schlag.

[AndersI]

Actually, you should probably lower it, to get more iterations. The largest dev in your picture is 0.023, so with a 0.07 tolerance PC-DMIS will think that's "good enough". But mainly, listen to Matthew - he knows those things!

[Matthew D. Hoedeman]

Well, the ONLY time I have ever had Pcdmis run through the iterative more than twice is when the part was such a POS that my standard POINT TARGET RADIUS of 0.5mm (0.020") wasn't big enough for the crappy part. I use 0.5mm and 0.05mm (fixture tolerance) standard forever. I was told that if you used a ZERO fixture tolerance that it would run through the alignment as many times as you had for MAX ITERATIONS. This is NOT true. I've used ZERO fixture tolerance and still only had it go through twice. I use iterative alignments on sheet metal part holding fixtures, so, vectors and nominals not "square" to the world, and still it will only go through twice (measure all always). ONLY time it did more than 2 was when the target radius wasn't big enough for a garbage part. Keep in mind when I do this on fixtures, I do a minimum of 3 hits per net pad (datum simulator, whatever you want to call them), and there is usually at least 4, but I've had up to 27 net pads for a part (yes, that was insane!). No matter the fixture tolerance, 2 times through. And yes, there is ALWAYS deviation if using more than the minimum features.

[Matthew D. Hoedeman]

a 6 hit iterative alignment should show zero deviation for the 6 hits after it solves. 3X, 2Y, 1Z, all should show zero deviation.

[Matthew D. Hoedeman]

Looking at your features, your VECTORS are wrong for the iterative action you want to do with them.

1B is mostly Y
2B is mostly X
3B is mostly X
5B is mostly X
6B is mostly Y
7B is mostly Z

So you should be using 2B, 3B, 5B for 'level'. 1B & 6B for rotate, 7B for origin

And those vectors are way too far (IMO) from any axis to use for an iterative alignment. Close to 45 degrees? BAD choice for an iterative alignment feature.

[Marken199]

Thanks Mattew. That's the problem.... it was about 32 degrees. I rotated 32 degrees to square up the coordinate system and recalculated vector touches, then did iterative alignment. It resolved perfectly... I then rotated -32 degrees from there. All good. Thanks!