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Legacy TP - NoOK, Xact TP - OK

Vladimir
Recently we had a dispute, for many years we measured a part according to the program sent to us by our collegues from another country, I am forbidden to doubt their qualifications. They used an legacy method for measuring TP, everything was in order until we started having problems with the cnc producing this part, some holes went out of tolerance, for the sake of interest I tried to apply xact and for these measurements it is not ideal but in the tolerance zone, now we do not know what to do, because our parts do not pass through the old dimensions, but the repair service says that it cannot find the problem, I am still a beginner and do not want to go against great minds, but I just wonder how it would be more correct. Here measurements of the same part, and we use iterative alignment.
Have a great sunny weekend everyone Slight smile
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  • In both cases A level, B origin, C one of the six holes to Y- according to drawing

    Are you sure about this? One of the holes PA should then be at zero deviation (in legacy evaluation). Could it be that a 2D-bestfit is done after the level/rotate alignment (as it should be done)?
    Xact does this for you, according to the datum structure.

    Possible to post the alignment code?
  • yes, here is the code from the program provided for us
    Part 1 
    PNT1 =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
THEO/<-13.239,32.138,10.2>,<0,0,1>
ACTL/<121.514,277.054,-720.653>,<0.0000705,-0.0006548,0.9999998>
TARG/<-13.239,32.138,10.2>,<0,0,1>
SHOW FEATURE PARAMETERS=YES
SURFACE=THEO_THICKNESS,0
MEASURE MODE=NOMINALS
RMEAS=NONE,NONE,NONE
AUTO WRIST=NO
GRAPHICAL ANALYSIS=NO
FEATURE LOCATOR=NO,NO,""
SHOW CONTACT PARAMETERS=YES
AVOIDANCE MOVE=BOTH,DISTANCE=20
SHOW HITS=NO
PNT2 =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
THEO/<-21.993,-25.32,10.2>,<0,0,1>
ACTL/<121.121,218.934,-720.688>,<0.0000705,-0.0006548,0.9999998>
TARG/<-21.993,-25.32,10.2>,<0,0,1>
SHOW FEATURE PARAMETERS=YES
SURFACE=THEO_THICKNESS,0
MEASURE MODE=NOMINALS
RMEAS=NONE,NONE,NONE
AUTO WRIST=NO
GRAPHICAL ANALYSIS=NO
FEATURE LOCATOR=NO,NO,""
SHOW CONTACT PARAMETERS=YES
AVOIDANCE MOVE=BOTH,DISTANCE=20
SHOW HITS=NO
PNT3 =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
THEO/<32.524,-3.431,10.2>,<0,0,1>
ACTL/<171.92,248.445,-720.676>,<0.0000705,-0.0006548,0.9999998>
TARG/<32.524,-3.431,10.2>,<0,0,1>
SHOW FEATURE PARAMETERS=YES
SURFACE=THEO_THICKNESS,0
MEASURE MODE=NOMINALS
RMEAS=NONE,NONE,NONE
AUTO WRIST=NO
GRAPHICAL ANALYSIS=NO
FEATURE LOCATOR=NO,NO,""
SHOW CONTACT PARAMETERS=YES
AVOIDANCE MOVE=BOTH,DISTANCE=20
SHOW HITS=NO
PNT4 =FEAT/CONTACT/VECTOR POINT/DEFAULT,CARTESIAN
THEO/<18.15,27.13,10.2>,<0,0,1>
ACTL/<153.297,276.618,-720.65>,<0.0000705,-0.0006548,0.9999998>
TARG/<18.15,27.13,10.2>,<0,0,1>
SHOW FEATURE PARAMETERS=YES
SURFACE=THEO_THICKNESS,0
MEASURE MODE=NOMINALS
RMEAS=NONE,NONE,NONE
AUTO WRIST=NO
GRAPHICAL ANALYSIS=NO
FEATURE LOCATOR=NO,NO,""
SHOW CONTACT PARAMETERS=YES
AVOIDANCE MOVE=BOTH,DISTANCE=20
SHOW HITS=NO
B CIR =FEAT/CONTACT/CIRCLE/DEFAULT,CARTESIAN,IN,LEAST_SQR
THEO/<0,0,10.2>,<0,0,1>,45
ACTL/<139.235,247.162,-720.657>,<0.0002473,-0.0008993,0.9999996>,45.032
TARG/<0,0,10.2>,<0,0,1>
START ANG=0,END ANG=0
ANGLE VEC=<1,0,0>
DIRECTION=CCW
SHOW FEATURE PARAMETERS=YES
REMEASURE=NO
SURFACE=THEO_THICKNESS,0
MEASURE MODE=NOMINALS
RMEAS=NONE,NONE,NONE
AUTO WRIST=NO
GRAPHICAL ANALYSIS=NO
FEATURE LOCATOR=NO,NO,""
SHOW CONTACT PARAMETERS=YES
NUMHITS=4,DEPTH=3,PITCH=0
SAMPLE HITS=3,SPACER=3
AVOIDANCE MOVE=BOTH,DISTANCE=20
FIND HOLE=DISABLED,ONERROR=NO,READ POS=NO
SHOW HITS=NO
C CIR =FEAT/CONTACT/CIRCLE/DEFAULT,CARTESIAN,IN,LEAST_SQR
THEO/<-4.307,-32.724,10.2>,<0,0,1>,11.5
ACTL/<139.704,214.105,-720.693>,<0.000345,-0.0023923,0.9999971>,11.548
TARG/<-4.307,-32.718,10.2>,<0,0,1>
START ANG=0,END ANG=360
ANGLE VEC=<1,0,0>
DIRECTION=CCW
SHOW FEATURE PARAMETERS=YES
REMEASURE=NO
SURFACE=THEO_THICKNESS,0
MEASURE MODE=NOMINALS
RMEAS=NONE,NONE,NONE
AUTO WRIST=NO
GRAPHICAL ANALYSIS=NO
FEATURE LOCATOR=NO,NO,""
SHOW CONTACT PARAMETERS=YES
NUMHITS=4,DEPTH=3,PITCH=0
SAMPLE HITS=3,SPACER=3
AVOIDANCE MOVE=BOTH,DISTANCE=20
FIND HOLE=DISABLED,ONERROR=NO,READ POS=NO
SHOW HITS=NO
A1 =ALIGNMENT/START,RECALL:STARTUP,LIST=YES
ALIGNMENT/ITERATE
PNT TARGET RAD=0.1,START LABEL=,FIXTURE TOL=0.05,ERROR LABEL=
MEAS ALL FEAT=ALWAYS,MAX ITERATIONS=1,LEVEL AXIS=ZAXIS,ROTATE AXIS=XAXIS,ORIGIN AXIS=YAXIS
LEVEL=PNT1,PNT2,PNT3,PNT4,,
ROTATE=B CIR,C CIR,,
ORIGIN=B CIR,,
ALIGNMENT/END
MODE/DCC
CLEARP/ZPLUS,35,ZPLUS,35,ON
PNT5 =FEAT/POINT,CARTESIAN
THEO/<5.216,32.796,0.118>,<0,0,1>
ACTL/<5.217,32.796,-0.659>,<0,0,1>
MEAS/POINT,1,WORKPLANE
MOVE/CLEARPLANE
HIT/BASIC,NORMAL,<5.216,32.796,0.118>,<0,0,1>,<5.217,3 2.796,-0.659>,USE THEO=YES
ENDMEAS/
PNT6 =FEAT/POINT,CARTESIAN
THEO/<-27.029,20.012,0.111>,<0,0,1>
ACTL/<-27.029,20.012,-0.652>,<0,0,1>
MEAS/POINT,1,WORKPLANE
MOVE/CLEARPLANE
HIT/BASIC,NORMAL,<-27.029,20.012,0.111>,<0,0,1>,<-27.029,20.012,-0.652>,USE THEO=YES
ENDMEAS/
PNT7 =FEAT/POINT,CARTESIAN
THEO/<-5.7,-34.325,0.074>,<0,0,1>
ACTL/<-5.7,-34.328,-0.609>,<0,0,1>
MEAS/POINT,1,WORKPLANE
MOVE/CLEARPLANE
HIT/BASIC,NORMAL,<-5.7,-34.325,0.074>,<0,0,1>,<-5.7,-34.328,-0.609>,USE THEO=YES
ENDMEAS/
PNT8 =FEAT/POINT,CARTESIAN
THEO/<29.959,11.994,0.102>,<0,0,1>
ACTL/<29.96,11.995,-0.627>,<0,0,1>
MEAS/POINT,1,WORKPLANE
MOVE/CLEARPLANE
HIT/BASIC,NORMAL,<29.959,11.994,0.102>,<0,0,1>,<29.96, 11.995,-0.627>,USE THEO=YES
ENDMEAS/
A PLN =FEAT/PLANE,CARTESIAN,TRIANGLE,NO
THEO/<0.611,7.62,0.101>,<0.0000598,-0.0006592,0.9999998>
ACTL/<0.612,7.618,-0.637>,<-0.0003234,0.0007474,0.9999997>
CONSTR/PLANE,BFRE,PNT5,PNT6,PNT7,PNT8,,
OUTLIER_REMOVAL/OFF,3
FILTER/OFF,WAVELENGTH=0
MOVE/CLEARPLANE
A2 =ALIGNMENT/START,RECALL:A1,LIST=YES
ALIGNMENT/LEVEL,ZPLUS,A PLN
ALIGNMENT/TRANS,ZAXIS,A PLN
ALIGNMENT/END
  • in reply to Vladimir
    Part 2 
    dim loc3= position of circle c cir units=mm ,$
graph=off text=off mult=10.00 output=both fit to datums=off dev perpen centerline=off display=diameter
ax meas nominal +tol -tol bonus dev outtol
pr 33.053 33.000 0.053
pa 262.512 262.500 0.012
df 11.548 11.500 0.100 0.100 0.048 0.000 ------#--
d1 45.032 45.000 0.025 0.000 circle b cir at rfs
d2 plane a pln at rfs
tp 0.107 rfs 0.300 0.000 0.107 0.000 ---#-----
end of dimension loc3
cir3 =feat/contact/circle/default,cartesian,in,least_sqr
theo/<26.181,-20.089,10.125>,<-0.0006008,0.0002778,0.9999998>,11.5
actl/<26.191,-20.164,10.805>,<0.0020137,-0.0017493,0.9999964>,11.542
targ/<26.175,-20.086,10.125>,<-0.0006008,0.0002778,0.9999998>
start ang=0,end ang=360
angle vec=<0.5000004,0.8660252,0.0000598>
direction=ccw
show feature parameters=yes
remeasure=no
surface=theo_thickness,0
measure mode=nominals
rmeas=none,none,none
auto wrist=no
circular moves=no
clearplane=no
graphical analysis=no
feature locator=no,no,""
show contact parameters=yes
numhits=4,depth=3,pitch=0
sample hits=3,spacer=3
avoidance move=both,distance=20
find hole=disabled,onerror=no,read pos=no
show hits=no
dim loc3= position of circle cir3 units=mm ,$
graph=off text=off mult=10.00 output=both fit to datums=off dev perpen centerline=off display=diameter
ax meas nominal +tol -tol bonus dev outtol
pr 33.042 33.000 0.042
pa 322.424 322.500 -0.076
df 11.542 11.500 0.100 0.100 0.042 0.000 ------#--
d1 45.032 45.000 0.025 0.000 circle b cir at rfs
d2 plane a pln at rfs
tp 0.121 rfs 0.300 0.000 0.121 0.000 ---#-----
end of dimension loc3
cir4 =feat/contact/circle/default,cartesian,in,least_sqr
theo/<30.488,12.629,10.125>,<-0.000541,-0.0003814,0.9999998>,11.5
actl/<30.491,12.576,10.833>,<0.0018994,0.0004675,0.9999 981>,11.549
targ/<30.483,12.625,10.125>,<-0.000541,-0.0003814,0.9999998>
start ang=0,end ang=360
angle vec=<-0.4999996,0.8660256,0.0000598>
direction=ccw
show feature parameters=yes
remeasure=no
surface=theo_thickness,0
measure mode=nominals
rmeas=none,none,none
auto wrist=no
circular moves=no
clearplane=no
graphical analysis=no
feature locator=no,no,""
show contact parameters=yes
numhits=4,depth=3,pitch=0
sample hits=3,spacer=3
avoidance move=both,distance=20
find hole=disabled,onerror=no,read pos=no
show hits=no
dim loc3= position of circle cir4 units=mm ,$
graph=off text=off mult=10.00 output=both fit to datums=off dev perpen centerline=off display=diameter
ax meas nominal +tol -tol bonus dev outtol
pr 32.984 33.000 -0.016
pa 22.440 22.500 -0.060
df 11.549 11.500 0.100 0.100 0.049 0.000 ------#--
d1 45.032 45.000 0.025 0.000 circle b cir at rfs
d2 plane a pln at rfs
tp 0.076 rfs 0.300 0.000 0.076 0.000 --#------
end of dimension loc3
cir5 =feat/contact/circle/default,cartesian,in,least_sqr
theo/<4.307,32.718,10.125>,<0.0000598,-0.0006592,0.9999998>,11.5
actl/<4.305,32.665,10.859>,<-0.0000744,0.0006359,0.9999998>,11.55
targ/<4.308,32.711,10.125>,<0.0000598,-0.0006592,0.9999998>
start ang=0,end ang=360
angle vec=<-1,0.0000005,0.0000598>
direction=ccw
show feature parameters=yes
remeasure=no
surface=theo_thickness,0
measure mode=nominals
rmeas=none,none,none
auto wrist=no
circular moves=no
clearplane=no
graphical analysis=no
feature locator=no,no,""
show contact parameters=yes
numhits=4,depth=3,pitch=0
sample hits=3,spacer=3
avoidance move=both,distance=20
find hole=disabled,onerror=no,read pos=no
show hits=no
dim loc3= position of circle cir5 units=mm ,$
graph=off text=off mult=10.00 output=both fit to datums=off dev perpen centerline=off display=diameter
ax meas nominal +tol -tol bonus dev outtol
pr 32.961 33.000 -0.039
pa 82.502 82.500 0.002
df 11.550 11.500 0.100 0.100 0.050 0.000 ------#--
d1 45.032 45.000 0.025 0.000 circle b cir at rfs
d2 plane a pln at rfs
tp 0.078 rfs 0.300 0.000 0.078 0.000 --#------
end of dimension loc3
cir6 =feat/contact/circle/default,cartesian,in,least_sqr
theo/<-26.181,20.089,10.125>,<0.0006008,-0.0002778,0.9999998>,11.5
actl/<-26.185,20.019,10.86>,<-0.0007274,-0.0007158,0.9999995>,11.546
targ/<-26.175,20.086,10.125>,<0.0006008,-0.0002778,0.9999998>
start ang=0,end ang=360
angle vec=<-0.5000004,-0.8660252,0.0000598>
direction=ccw
show feature parameters=yes
remeasure=no
surface=theo_thickness,0
measure mode=nominals
rmeas=none,none,none
auto wrist=no
circular moves=no
clearplane=no
graphical analysis=no
feature locator=no,no,""
show contact parameters=yes
numhits=4,depth=3,pitch=0
sample hits=3,spacer=3
avoidance move=both,distance=20
find hole=disabled,onerror=no,read pos=no
show hits=no
dim loc3= position of circle cir6 units=mm ,$
graph=off text=off mult=10.00 output=both fit to datums=off dev perpen centerline=off display=diameter
ax meas nominal +tol -tol bonus dev outtol
pr 32.972 33.000 -0.028
pa 142.585 142.500 0.085
df 11.546 11.500 0.100 0.100 0.046 0.000 ------#--
d1 45.032 45.000 0.025 0.000 circle b cir at rfs
d2 plane a pln at rfs
tp 0.112 rfs 0.300 0.000 0.112 0.000 ---#-----
end of dimension loc3
cir7 =feat/contact/circle/default,cartesian,in,least_sqr
theo/<-30.488,-12.629,10.125>,<0.000541,0.0003814,0.9999998>,11.5
actl/<-30.486,-12.701,10.835>,<-0.000272,-0.0015425,0.9999988>,11.559
targ/<-30.483,-12.625,10.125>,<0.000541,0.0003814,0.9999998>
start ang=0,end ang=360
angle vec=<0.4999996,-0.8660256,0.0000598>
direction=ccw
show feature parameters=yes
remeasure=no
surface=theo_thickness,0
measure mode=nominals
rmeas=none,none,none
auto wrist=no
circular moves=no
clearplane=no
graphical analysis=no
feature locator=no,no,""
show contact parameters=yes
numhits=4,depth=3,pitch=0
sample hits=3,spacer=3
avoidance move=both,distance=20
find hole=disabled,onerror=no,read pos=no
show hits=no
dim loc3= position of circle cir7 units=mm ,$
graph=off text=off mult=10.00 output=both fit to datums=off dev perpen centerline=off display=diameter
ax meas nominal +tol -tol bonus dev outtol
pr 33.024 33.000 0.024
pa 202.591 202.500 0.091
df 11.559 11.500 0.100 0.100 0.059 0.000 -------#-
d1 45.032 45.000 0.025 0.000 circle b cir at rfs
d2 plane a pln at rfs
tp 0.115 rfs 0.300 0.000 0.115 0.000 ---#-----
end of dimension loc3
  • in reply to Vladimir
    I think this is a weighty enough argument to give to my boss Smiley
  • in reply to KIRBSTER269
    I will bring up this moment for discussion today
  • in reply to Kp61dude!
    Our city is very far from the space industry, but I understand you Smiley
  • in reply to KIRBSTER269
    yes, I understand that, but no one else is interested in it except me
  • in reply to KIRBSTER269
    Ok, but I have one problem
    I write the correct program, measure the center hole (dat B) with three sample hits and use iterative alignment, but for this to be a cylinder I need to manually measure the hole twice at both levels, this will take much more time and my colleagues will not agree.
    How much it will be correct to use alignment in a circle in manual mode and only in dcc to align with a cylinder ?
  • This one looks like it has been in discussion for a while and it is quite a common cause of confusion so I thought I'd help out. As many people have said, the original program is wrong. Based on your sketch of the part and the position call out you are trying to measure, the correct approach should be as follows....

    1) Measure the top face (datum A) as a plane, taking enough points to capture the form error (flatness).
    2) Measure the centre bore (datum B) as a cylinder.
    3) Measure the 6 x holes as cylinders.
    4) Dimension the holes.

    To dimension using XactMeasure (feature control frame reporting), add a DATDEF command defining the top plane as datum A. Add another DATDEF command defining the centre cylinder as datum B. INSERT>DIMENSION>POSITION. Select all 6 holes and build the feature control frame - position, Ø0.3 to A (primary), B (secondary).

    To dimension using Legacy dimensions you need to create the A,B alignment. Level ZPLUS to the top plane and origin Z. Origin X & Y to the centre cylinder. Click the BESTFIT button. Select all 6 holes, 2D no translation, 2D plane = ZPLUS then click COMPUTE and OK. INSERT>DIMENSION>POSITION, select all 6 holes, enter the 0.3 tolerance and hit create - you do not need to select datums as it reports relative to your current alignment which simulates the datum reference frame.

    Both methods should yield the same results but it is very important that the nominal (THEO) X,Y,Z,I,J & K values are correct for all features, especially if you have had to manually type them in.


    My justification for saying the original program is wrong is this...

    There is no tertiary datum for the position call out - it is simply |Ø0.3|A|B|. A is the primary and B is the secondary so we must level to A and origin to B but since there is no rotational constraint, the 6 holes are free to rotate around B until they are optimized. The original program ignores this and constrains rotation using one of the holes rather than best fitting all 6 as a set. The original program also measures datum B and the 6 holes as circles and as such is not satisfying the position requirement. Position relates to the entire axis of the feature. By measuring the holes as circles it is only evaluating a point at whatever depth the hole was measured. It is ignoring any orientation error that may be present and could result in passing parts that are actually bad and would not assemble. In addition to this, in the legacy position dimensions, it references the two datums in the wrong order - D1 references datum B when it should be A and D2 references A when it should be B.

    In terms of my credentials to back up this evaluation. I have been a CMM programmer for over 20 years having worked as an inspector, (5 years) quality engineer (5 years), hexagon applications engineer (8 years) and software technical specialist (2 years). I have taught both first principles measurement and GD&T classes for Hexagon and on behalf of the National Physical Laboratory (UK) and I have been heavily involved in the development of the new geometric tolerance command for PC-Dmis 2020 R2.
  • in reply to KIRBSTER269
    manual alignment is just to locate the part on the machine, you don't use those features for anything else. In DCC mode you can create a auto plane (A), auto cylinder(B), another auto cylinder for clocking, You don't have to make manual hits. cleaner program also
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