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Issues with measuring holes at 90 degrees.

metrology_dept117

I've never been able to get this to work. Everything works great when I'm measuring holes level to the surface plate, but as soon as I articulate the probe to A90B0, A90B90, or any other combination, all of my holes come out at least .010" shifted from the actual values. 

I'm guessing it's something to do with my alignment, but it seems like I've tried everything. I've used the normal level, created a plane on that 90deg surface and leveled to that, articulated the probe first before measuring the plane and then leveling to that, and I'm just stuck and don't know how to get this to work. Can't find any other forum posts relating to this problem.

The main issue here is I'm forced to re-fixture the part 6 different times and write 6 different programs just to check every hole in every face. It's extremely time consuming and I'm hoping someone has an easy solution that I'm completely missing.

I can write a quick program just showing the issue if that helps.

  • 0 in reply to WilliamL 

    PART NAME  : AXS83016 HOLES
REV NUMBER : E
SER NUMBER :
STATS COUNT : 1
 
STARTUP    =ALIGNMENT/START,RECALL:USE_PART_SETUP,LIST=YES
            ALIGNMENT/END
            MODE/MANUAL
            MOVESPEED/ 100
            FORMAT/TEXT,OPTIONS, ,HEADINGS,SYMBOLS, ;NOM,TOL,MEAS,DEV,OUTTOL, ,
            LOADPROBE/2BY20
            TIP/T1A0B0, SHANKIJK=0, 0, 1, ANGLE=0
PLN1       =FEAT/PLANE,CARTESIAN,TRIANGLE
            THEO/<0.303,0.338,0.192>,<0,0,1>
            ACTL/<12.5,11.474,-2.135>,<0.0026072,0.0003248,0.9999965>
            MEAS/PLANE,3
              HIT/BASIC,NORMAL,<1.75,1.126,0.192>,<0,0,1>,<11.936,11.917,-2.134>,USE THEO=YES
              HIT/BASIC,NORMAL,<1.276,-1.051,0.192>,<0,0,1>,<13.095,11.917,-2.137>,USE THEO=YES
              HIT/BASIC,NORMAL,<-2.118,0.939,0.192>,<0,0,1>,<12.468,10.589,-2.134>,USE THEO=YES
            ENDMEAS/
A1         =ALIGNMENT/START,RECALL:STARTUP,LIST=YES
              ALIGNMENT/LEVEL,ZPLUS,PLN1
              ALIGNMENT/TRANS,ZAXIS,PLN1
            ALIGNMENT/END
LIN1       =FEAT/LINE,CARTESIAN,UNBOUNDED
            THEO/<-2.146,-1.997,-0.183>,<1,0,0>
            ACTL/<14.152,10.596,-0.119>,<-0.0027556,0.9999962,0>
            MEAS/LINE,2,ZPLUS
              HIT/BASIC,NORMAL,<-2.146,-1.998,-0.179>,<0,-1,0>,<14.152,10.596,-0.119>,USE THEO=YES
              HIT/BASIC,NORMAL,<2.194,-1.998,-0.187>,<0,-1,0>,<14.149,11.635,-0.119>,USE THEO=YES
            ENDMEAS/
A2         =ALIGNMENT/START,RECALL:A1,LIST=YES
              ALIGNMENT/ROTATE,XPLUS,TO,LIN1,ABOUT,ZPLUS
              ALIGNMENT/TRANS,YAXIS,LIN1
            ALIGNMENT/END
PNT1       =FEAT/POINT,CARTESIAN
            THEO/<-3,2.373,-0.139>,<-1,0,0>
            ACTL/<7.05,1.332,-0.131>,<-1,0,0>
            MEAS/POINT,1,WORKPLANE
              HIT/BASIC,NORMAL,<-3,2.373,-0.139>,<-1,0,0>,<7.05,1.332,-0.131>,USE THEO=YES
            ENDMEAS/
A3         =ALIGNMENT/START,RECALL:A2,LIST=YES
              ALIGNMENT/TRANS,XAXIS,PNT1
            ALIGNMENT/END
            MODE/DCC
            CLEARP/ZPLUS,0.25,ZPLUS,0,ON
PLN2       =FEAT/PLANE,CARTESIAN,TRIANGLE
            THEO/<3.234,1.788,0>,<0,0,1>
            ACTL/<3.234,1.788,0.001>,<0.0000908,-0.0002629,1>
            MEAS/PLANE,12
              MOVE/CLEARPLANE
              HIT/BASIC,NORMAL,<5.346,3.556,0>,<0,0,1>,<5.346,3.556,0.001>,USE THEO=YES
              HIT/BASIC,NORMAL,<5.292,2.105,0>,<0,0,1>,<5.292,2.105,0>,USE THEO=YES
              HIT/BASIC,NORMAL,<5.069,0.462,0>,<0,0,1>,<5.069,0.462,0>,USE THEO=YES
              HIT/BASIC,NORMAL,<4.293,0.851,0>,<0,0,1>,<4.293,0.851,0>,USE THEO=YES
              HIT/BASIC,NORMAL,<4.764,2.858,0>,<0,0,1>,<4.764,2.858,0.001>,USE THEO=YES
              HIT/BASIC,NORMAL,<3.777,1.782,0>,<0,0,1>,<3.777,1.781,0>,USE THEO=YES
              HIT/BASIC,NORMAL,<3.373,0.323,0>,<0,0,1>,<3.373,0.322,0>,USE THEO=YES
              HIT/BASIC,NORMAL,<2.065,2.083,0>,<0,0,1>,<2.066,2.083,0>,USE THEO=YES
              HIT/BASIC,NORMAL,<1.962,0.604,0>,<0,0,1>,<1.962,0.603,0>,USE THEO=YES
              HIT/BASIC,NORMAL,<0.82,0.508,0>,<0,0,1>,<0.821,0.508,0.001>,USE THEO=YES
              HIT/BASIC,NORMAL,<1.51,3.512,0>,<0,0,1>,<1.51,3.511,0.001>,USE THEO=YES
              HIT/BASIC,NORMAL,<0.54,2.812,0>,<0,0,1>,<0.54,2.812,0.001>,USE THEO=YES
            ENDMEAS/
LIN2       =FEAT/LINE,CARTESIAN,UNBOUNDED
            THEO/<0.664,0,-0.141>,<1,0,0>
            ACTL/<0.664,0,-0.141>,<1,-0.0000451,0>
            MEAS/LINE,4,ZPLUS
              MOVE/CLEARPLANE
              HIT/BASIC,NORMAL,<0.664,0,-0.151>,<0,-1,0>,<0.664,0,-0.151>,USE THEO=YES
              HIT/BASIC,NORMAL,<1.983,0,-0.153>,<0,-1,0>,<1.983,0,-0.153>,USE THEO=YES
              HIT/BASIC,NORMAL,<3.746,0,-0.118>,<0,-1,0>,<3.746,0,-0.118>,USE THEO=YES
              HIT/BASIC,NORMAL,<5.328,0,-0.142>,<0,-1,0>,<5.329,0,-0.142>,USE THEO=YES
            ENDMEAS/
LIN3       =FEAT/LINE,CARTESIAN,UNBOUNDED
            THEO/<0,0.608,-0.112>,<0,1,0>
            ACTL/<0,0.607,-0.112>,<0.0002027,1,0>
            MEAS/LINE,3,ZPLUS
              MOVE/CLEARPLANE
              HIT/BASIC,NORMAL,<0,0.608,-0.107>,<-1,0,0>,<0,0.607,-0.107>,USE THEO=YES
              HIT/BASIC,NORMAL,<0,1.603,-0.126>,<-1,0,0>,<0,1.603,-0.126>,USE THEO=YES
              HIT/BASIC,NORMAL,<0,3.292,-0.103>,<-1,0,0>,<0.001,3.292,-0.103>,USE THEO=YES
            ENDMEAS/
A4         =ALIGNMENT/START,RECALL:STARTUP,LIST=YES
              ALIGNMENT/LEVEL,ZPLUS,PLN2
              ALIGNMENT/TRANS,ZAXIS,PLN2
              ALIGNMENT/ROTATE,XPLUS,TO,LIN2,ABOUT,ZPLUS
              ALIGNMENT/TRANS,YAXIS,LIN2
              ALIGNMENT/TRANS,XAXIS,LIN3
            ALIGNMENT/END
            MOVE/CLEARPLANE
            LOADPROBE/1BY20CYLINDER
            MOVE/CLEARPLANE
            TIP/T1A90B-90, SHANKIJK=-0.013, -1, 0.002, ANGLE=179.99
            MOVE/POINT,NORMAL,<2.603,-0.769,0.361>
            MOVE/CLEARPLANE
CIR1       =FEAT/CONTACT/CIRCLE/DEFAULT,CARTESIAN,IN,LEAST_SQR
            THEO/<3,0,-0.222>,<0,-1,0>,0.118
            ACTL/<2.988,0,-0.218>,<0,-1,0>,0.102
            TARG/<3,0,-0.222>,<0,-1,0>
            START ANG=0,END ANG=360
            ANGLE VEC=<1,0,0>
            DIRECTION=CCW
            SHOW FEATURE PARAMETERS=NO
            SHOW CONTACT PARAMETERS=YES
              NUMHITS=5,DEPTH=0.079,PITCH=0
              SAMPLE METHOD=SAMPLE_HITS
              SAMPLE HITS=0,SPACER=0
              AVOIDANCE MOVE=BOTH,DISTANCE BEFORE=0.394,DISTANCE AFTER=0.394,DIRECTION=ALONG FEATURE VECTOR
              FIND HOLE=DISABLED,ONERROR=NO,READ POS=NO
            SHOW HITS=NO
DIM LOC1= LOCATION OF CIRCLE CIR1  UNITS=IN ,$
GRAPH=OFF  TEXT=OFF  MULT=10.00  OUTPUT=BOTH  HALF ANGLE=NO
AX    NOMINAL       +TOL       -TOL       MEAS        DEV     OUTTOL
X        3.000      0.005      0.005      2.988     -0.012      0.007 <--------
Z       -0.222      0.005      0.005     -0.218      0.004      0.000 --------#
D        0.118      0.005      0.005      0.102     -0.016      0.011 <--------
END OF DIMENSION LOC1

  • 0

    This may be resolved. I had to level to the plane at 90 degrees and align everything else as usual.

    I swear up and down I've tried this in the past and it didn't help whatsoever. Thank you guys for all your help.

  • 0 in reply to metrology_dept117

    You shouldn't normally have to align to each side of the part after establishing a solid base alignment. If you're using more than 1 probe build to inspect these parts, which it looks like you are, then a calibration issue seems possible. That's the reason I asked about a master probe. 

  • 0 in reply to Zen Cat

    Yeah, you could be right, I just tried to implement this into a program and it completely failed.

    Problem is I don't even know how to begin fixing the calibration. I'm totally lost.

  • 0 in reply to metrology_dept117

    Search Master probe in this forum. There are numerous threads. Here's one that explains the process and rationale. 

    "Master Probe" question - PC-DMIS for CMMs - PC-DMIS - Nexus Community (hexagon.com)

  • 0

    Accuracy in CMM relies on minimizing cosine error whenever possible. Determining the center of a circle is a key method to reduce variation between the measured and actual values. In certain conditions, the number of sample hits can significantly influence the accuracy, especially when measuring circles on thin materials, as they help better define the surface for precise measurements.

  • 0 in reply to metrology_dept117

    Hexagon has a free pc-dmis basics that you should take. If you don't understand the calibration and what effects it can have, then you should insist that you be sent to onsite training at a hexagon facility for the 101 / 201 training. 

    https://learning.hexagonmi.com/login.asp 

  • 0 in reply to metrology_dept117

    I'm sorry. I assumed your styli were correctly calibrated.  After reading the comments after my post, I feel you should first calibrate correctly so that all your styli and tip angles relate to one another correctly.

    Basically, assign a MASTER probe.  Short and stiff is best.  Calibrate in A0B0 and when asked if the sphere has moved, answer YES.  After this is complete, calibrate all other styli and tip angles answering NO when asked if the sphere has moved.

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