Positon interpretation

[tracee]

I'm using the CMM to check a pretty basic part, essentially a rectangle with 8 holes placed through it. I wrote a program and proceeded to start checking parts and a common theme occurred (the part is near symmetrical) when I measured the top side everything would measure in spec. When I measured the part flipped over all distances would measure in spec, but multiple hole position callouts would show as rejected saying they are outtol/the icon showing red.

I assumed somehow I was missing something and rechecked my datum references and call outs(everything checked out). The part is pretty thin (.090") so I was measuring the holes as circles......I had our CNC operator make me a thicker part so I could measure the holes as cylinders......same result. I added additional information to check; each individual hole distance from the other holes, distance to all 4 edges, rechecked the diameter, all clearly in spec. I double checked these measurements with a vision system, everything passed. Everything seems to be 100% fine, but the program continues to tell me 1 side is in spec, when I flip it and measure the other side multiple holes are outtol in the position callout. Any idea what could be causing this? II'm just kind of stumped , any help would be appreciated.

[Darrollh]

You need to check your alignment. Something really square, I would take 4 hits for a plane, 2 for a line and 2 for another line. Use quick alignment then take your measurements.

[tracee]

That's what I'm using the top surface as a plane, front edge and left edge. I'm just perplexed that I can do 20 parts in a row and all check out, but soon as I flip it, it's consistently out of positon.

[DAN_M]

Two things immediately come to mind.

1) Your alignment surfaces must not be square to one another.

2) Your code is incorrect.

Can you look into #1..and report back...as well as post the code so we can dig into #2 for you?

[tracee]

Thanks for the responses, I'm pretty much a novice flying by the seat of his pants at this, so I appreciate any help

here is the alignment code:

STARTUP =ALIGNMENT/START,RECALL:USE_PART_SETUP,LIST=YES
ALIGNMENT/END
MODE/MANUAL
PREHIT/0.12
RETRACT/0.12
MOVESPEED/ 150
FORMAT/TEXT,OPTIONS, ,HEADINGS,SYMBOLS, ;NOM,TOL,MEAS,DEV,OUTTOL, ,
LOADPROBE/3
TIP/T1A0B0, SHANKIJK=0, 0, 1, ANGLE=0
PLN1 =FEAT/PLANE,CARTESIAN,TRIANGLE
THEO/<6.4944,7.6626,-15.9747>,<0.0002364,0.0131115,0.999914>
ACTL/<7.8722,7.6348,-15.8191>,<0.0006148,-0.0729915,0.9973324>
MEAS/PLANE,3
HIT/BASIC,NORMAL,<3.5131,7.5393,-15.9723>,<0.0002364,0.0131115,0.999914>,<3.7935,7. 5064,-15.826>,USE THEO=YES
HIT/BASIC,NORMAL,<7.47,7.9254,-15.9783>,<0.0002364,0.0131115,0.999914>,<8.1883,7. 7506,-15.8108>,USE THEO=YES
HIT/BASIC,NORMAL,<8.5001,7.5231,-15.9733>,<0.0002364,0.0131115,0.999914>,<11.6349,7 .6474,-15.8205>,USE THEO=YES
ENDMEAS/
A1 =ALIGNMENT/START,RECALL:,LIST=YES
ALIGNMENT/LEVEL,ZPLUS,PLN1
ALIGNMENT/TRANS,ZAXIS,PLN1
ALIGNMENT/END
LIN1 =FEAT/LINE,CARTESIAN,UNBOUNDED
THEO/<2.6578,7.5064,-0.0589>,<0.9999682,0.0079789,0>
ACTL/<2.8338,6.007,-0.0957>,<0.999755,0.0221324,0>
MEAS/LINE,2,ZPLUS
HIT/BASIC,NORMAL,<2.6578,7.5064,-0.059>,<0.0079789,-0.9999682,0>,<2.8338,6.007,-0.0945>,USE THEO=YES
HIT/BASIC,NORMAL,<3.4909,7.513,-0.0588>,<0.0079789,-0.9999682,0>,<5.4367,6.0646,-0.097>,USE THEO=YES
ENDMEAS/
A2 =ALIGNMENT/START,RECALL:A1,LIST=YES
ALIGNMENT/ROTATE,XPLUS,TO,LIN1,ABOUT,ZPLUS
ALIGNMENT/END
PNT1 =FEAT/POINT,CARTESIAN
THEO/<2.6428,7.5541,-0.0574>,<-1,0,0>
ACTL/<2.8604,6.0034,-0.1031>,<-0.9216687,-0.3868746,0.0292389>
MEAS/POINT,1,WORKPLANE
HIT/BASIC,NORMAL,<2.6428,7.5541,-0.0574>,<-1,0,0>,<2.8604,6.0034,-0.1031>,USE THEO=YES
ENDMEAS/
A3 =ALIGNMENT/START,RECALL:A2,LIST=YES
ALIGNMENT/TRANS,XAXIS,PNT1
ALIGNMENT/TRANS,YAXIS,LIN1
ALIGNMENT/END
COMMENT/OPER,NO,FULL SCREEN=NO,AUTO-CONTINUE=NO,
dcc
MODE/DCC
MOVE/POINT,NORMAL,<-0.1972,0.0702,-0.0575>
MOVE/POINT,NORMAL,<-0.1964,0.0592,0.7923>
MOVE/POINT,NORMAL,<1.2206,0.3680,0.7967>
PLN2 =FEAT/PLANE,CARTESIAN,TRIANGLE
THEO/<4.4342,0.3587,-0.0045>,<-0.0021723,-0.0318627,0.9994899>
ACTL/<4.4341,0.3518,0.0123>,<-0.0002715,0.075521,0.9971442>
MEAS/PLANE,6
HIT/BASIC,NORMAL,<1.221,0.3824,-0.0212>,<-0.0021723,-0.0318627,0.9994899>,<1.2209,0.3754,0.0081>,USE THEO=YES
HIT/BASIC,NORMAL,<2.315,0.5889,-0.0019>,<-0.0021723,-0.0318627,0.9994899>,<2.3149,0.583,-0.0065>,USE THEO=YES
HIT/BASIC,NORMAL,<3.7023,0.2342,0.004>,<-0.0021723,-0.0318627,0.9994899>,<3.7021,0.2271,0.0227>,USE THEO=YES
HIT/BASIC,NORMAL,<5.0633,0.4716,0.0073>,<-0.0021723,-0.0318627,0.9994899>,<5.0632,0.4653,0.0061>,USE THEO=YES
HIT/BASIC,NORMAL,<6.3291,0.2279,-0.0095>,<-0.0021723,-0.0318627,0.9994899>,<6.3289,0.2203,0.0247>,USE THEO=YES
HIT/BASIC,NORMAL,<7.9748,0.2471,-0.0056>,<-0.0021723,-0.0318627,0.9994899>,<7.9746,0.2399,0.0187>,USE THEO=YES
ENDMEAS/
A4 =ALIGNMENT/START,RECALL:A3,LIST=YES
ALIGNMENT/LEVEL,ZPLUS,PLN2
ALIGNMENT/TRANS,ZAXIS,PLN2
ALIGNMENT/END
MOVE/POINT,NORMAL,<7.9750,0.2542,0.2593>
MOVE/POINT,NORMAL,<-0.1785,-0.3902,0.2863>
MOVE/POINT,NORMAL,<-0.1784,-0.3954,-0.0016>
MOVE/POINT,NORMAL,<0.0800,-0.3955,-0.0018>
MOVE/POINT,NORMAL,<0.0813,-0.3944,-0.0612>
MOVE/POINT,NORMAL,<0.0407,-0.0950,-0.0324>
LIN2 =FEAT/LINE,CARTESIAN,UNBOUNDED
THEO/<0.0414,0.0006,-0.042>,<0.9999827,-0.00588,0>
ACTL/<-0.1603,-0.1571,-0.0435>,<0.9999616,0.0086862,-0.0011551>
MEAS/LINE,4,ZPLUS
HIT/BASIC,NORMAL,<0.0414,0.0024,-0.0332>,<-0.00588,-0.9999827,0>,<-0.1595,-0.1568,-0.0349>,USE THEO=YES
HIT/BASIC,NORMAL,<2.6793,-0.0154,-0.0376>,<-0.00588,-0.9999827,0>,<2.4784,-0.1345,-0.0425>,USE THEO=YES
HIT/BASIC,NORMAL,<7.2085,-0.0453,-0.0453>,<-0.00588,-0.9999827,0>,<7.0077,-0.0949,-0.0554>,USE THEO=YES
HIT/BASIC,NORMAL,<10.8875,-0.0605,-0.0518>,<-0.00588,-0.9999827,0>,<10.6868,-0.0627,-0.0661>,USE THEO=YES
ENDMEAS/
A5 =ALIGNMENT/START,RECALL:A4,LIST=YES
ALIGNMENT/ROTATE,XPLUS,TO,LIN2,ABOUT,ZPLUS
ALIGNMENT/END
MOVE/POINT,NORMAL,<10.8932,-0.6876,-0.0400>
MOVE/POINT,NORMAL,<-0.5881,-0.6586,-0.0208>
MOVE/POINT,NORMAL,<-0.5861,-0.0360,-0.0325>
MOVE/POINT,NORMAL,<-0.1272,0.0124,-0.0342>
MOVE/POINT,NORMAL,<-0.1272,0.0449,-0.0348>
PNT2 =FEAT/POINT,CARTESIAN
THEO/<-0.0011,0.0462,-0.0349>,<-1,0,0>
ACTL/<-0.0025,0.0464,-0.0349>,<-1,0,0>
MEAS/POINT,1,WORKPLANE
HIT/BASIC,NORMAL,<-0.0011,0.0462,-0.0349>,<-1,0,0>,<-0.0025,0.0464,-0.0349>,USE THEO=YES
ENDMEAS/
A6 =ALIGNMENT/START,RECALL:A5,LIST=YES
ALIGNMENT/TRANS,XAXIS,PNT2
ALIGNMENT/TRANS,YAXIS,LIN2
ALIGNMENT/END
MOVE/POINT,NORMAL,<-0.1717,0.0517,-0.0349>
MOVE/POINT,NORMAL,<-0.2757,0.7577,-0.0331>
MOVE/POINT,NORMAL,<-0.1827,0.7585,-0.0331>

[DAN_M]

Thanks!

A few things are jumping out at me.

1) I don't see a touchspeed command. Insert one in your code and make sure the touchspeed you use is the same as what you qualified your probe at.

2) Suggest forcing the NOMINAL X,Y,Z,I,J, and K values to "0" or "1" wherever applicable". Your vectors are skewed all through your program.

3) You should NEVER have an alignment that controls rotation that also doesn't control leveling first. When you're rotating, you're rotating ABOUT your leveled feature. A1 is fine....A2 is a huge "no-no'. I would have measured PLN1, LIN1, and then PNT1 one after another. Then, MY A1 would recall startup alignment and would level, rotate, and set the origin all at the same time. One could also make A2 by recalling startup, leveling, and then rotating... but they have to be TOGETHER, not separate.

4) The physical geometry that you're probing and making your alignments off of MUST not be square. If you have a part that is completely symmetrical, and one side measures differently than the other, and if your program is correct....then your part datums are messing you up.

[Schlag]

I would clean up all my line vectors and thoreticals. It makes for a much easy program to trouble shoot ? I see this and think you are writing a program from an imperfect part , which will give you a program with error already built into it. I don't know whats recomended on newer revs of DMIS but I will create 1 alignment that has all 6 DOF contained at the end of your DCC. LEVEL, ROTATE, X 0, Y 0 ,Z 0 all in a single alignment. After this is completed, never refer to any alignment "above" this one in the program. Also to keep things simple, more than 1 alignment in you MANUAL mode, doesn't do anything for you.

[tracee]

Thanks for the insight guys I am going to try to clean it up and give it another look.

[Matthew D. Hoedeman]

if you are flipping the part over, but just running the same program, you're using different 'datums' to check the part. You would need a NEW program that measures the same 'datums' in the same way to get the same results.

[VinniUSMC]

I'm using the CMM to check a pretty basic part, essentially a rectangle with 8 holes placed through it. I wrote a program and proceeded to start checking parts and a common theme occurred (the part is near symmetrical) when I measured the top side everything would measure in spec. When I measured the part flipped over all distances would measure in spec, but multiple hole position callouts would show as rejected saying they are outtol/the icon showing red.

...

Umm, the part is near symmetrical, or the part is symmetrical? Did you account for this being near symmetrical?

[louisd]

I'm with Matthew D. Hodeman. Let's say you are leveling to top of part, rotating to left edge, & origin to upper left intersect point.
If you flip part over, re-execute, you should rotate to RIGHT edge and orign to upper right intersect point.

[tracee]

Thanks for the insight and help on this one...new program for the flipped side was the way to go