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Composite position, threaded hole pattern

d.evans
I have a cylindrical part with a set of holes drilled 90 deg apart (3 o'clock, 6 o'clock, 9 o'clock and noon) around the circumference. Total of 8 holes- 4 at one level, 4 at another. The callout is very common to this type part, a PLTZF callout of .038" RFS to A|B, then a FRTZF callout of .018" RFS to A.

My question, if I have done this properly in my PC-DMIS program, is there any way that all 8 holes could pass for the upper PLTZF callout, and simultaneously all 8 holes fail the FRTZF callout? I can't see how they could, but when I executed a program recently that I've used on many of these same parts, this is exactly what the results show.

On a side-note, the drawing doesn't restrain all 6 degrees of freedom, so I chose a feature on the part that made sense to me to use to close that gap.

Thanks in advance Confused
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  • I am using the terms float and fit interchangeably - sorry for switching terminology on you. The best-fit alignment you are using is doing rotation about Z axis, and translation in X and Y. You are not allowing the holes to "float" from datum B, because your best fit is not allowing translation in Z axis. To deal with this, add a 2nd best-fit alignment(recalling the first best fit alignment) and choose "Specified Constraints", then use the radio buttons to lock down all degrees of freedom except translation in Z axis. Thing is, I'm not sure this method is available in 3.7MR3. If it is not, then I would deal with it this way (after the first best fit alignment):
    - construct midpoint between the 2 holes at 3 o'clock
    - construct midpoint between the 2 holes at 6 o'clock
    - construct midpoint between the 2 holes at 9 o'clock
    - construct midpoint between the 2 holes at 12 o'clock
    - construct plane from the 4 midpoints
    - set Z origin on plane

    (v3.7MR3 doesn't seem to have the tools you mentioned, at least not in the Best Fit Alignment dialog box). So if Im understanding this correctly, I should make sure I've got my cursor inside the 2D-best-fit (the one I normally do), then create a new alignment and only change the Z origin with that alignment?

    Like this?
    set origin =ALIGNMENT/START,RECALL:2dBF_8Holes, LIST= YES
    ALIGNMENT/TRANS,ZAXIS,MPLN1
    ALIGNMENT/END

    Doing it that way, I got the following result...

    DIM LOC19= TRUE POSITION OF CIRCLE C1 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
    Z -1.8535 -1.8544 -0.0009
    PR 1.6336 1.6324 -0.0012
    PA -89.9870 -90.0082 -0.0212
    DF 0.1042 0.0000 0.0000 0.1084 0.0042 0.0042 -------->
    TP RFS 0.0180 0.0000 0.0033 0.0000 -#-------
    END OF DIMENSION LOC19
    DIM LOC20= TRUE POSITION OF CIRCLE C2 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
    Z 1.8535 1.8543 0.0009
    DF 0.1042 0.0000 0.0000 0.1072 0.0030 0.0030 -------->
    TP RFS 0.0180 0.0000 0.0017 0.0000 #--------
    PR 1.6336 1.6314 -0.0022
    PA -89.9878 -89.8944 0.0934
    END OF DIMENSION LOC20
    DIM LOC21= TRUE POSITION OF CIRCLE C3 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
    Z -1.8535 -1.8503 0.0032
    DF 0.1042 0.0000 0.0000 0.1058 0.0016 0.0016 -------->
    TP RFS 0.0180 0.0000 0.0064 0.0000 ---#-----
    PR 1.6337 1.6364 0.0028
    PA -179.9876 179.9900 -0.0224
    END OF DIMENSION LOC21
    DIM LOC22= TRUE POSITION OF CIRCLE C4 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
    Z 1.8535 1.8527 -0.0008
    DF 0.1042 0.0000 0.0000 0.1064 0.0022 0.0022 -------->
    TP RFS 0.0180 0.0000 0.0015 0.0000 #--------
    PR 1.6327 1.6299 -0.0028
    PA 179.9879 -179.9293 0.0828
    END OF DIMENSION LOC22
    DIM LOC23= TRUE POSITION OF CIRCLE C5 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
    Z -1.8535 -1.8522 0.0013
    DF 0.1042 0.0000 0.0000 0.1072 0.0030 0.0030 -------->
    TP RFS 0.0180 0.0000 0.0026 0.0000 -#-------
    PR 1.6334 1.6335 0.0001
    PA 90.0118 90.0412 0.0294
    END OF DIMENSION LOC23
    DIM LOC24= TRUE POSITION OF CIRCLE C6 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
    Z 1.8535 1.8542 0.0007
    DF 0.1042 0.0000 0.0000 0.1067 0.0025 0.0025 -------->
    TP RFS 0.0180 0.0000 0.0014 0.0000 #--------
    PR 1.6336 1.6339 0.0004
    PA 90.0120 89.9267 -0.0854
    END OF DIMENSION LOC24
    DIM LOC25= TRUE POSITION OF CIRCLE C7 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
    Z -1.8535 -1.8581 -0.0047
    DF 0.1042 0.0000 0.0000 0.1151 0.0109 0.0109 -------->
    TP RFS 0.0180 0.0000 0.0093 0.0000 ----#----
    PR 1.6336 1.6293 -0.0042
    PA 0.0120 -0.0130 -0.0250
    END OF DIMENSION LOC25
    DIM LOC26= TRUE POSITION OF CIRCLE C8 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
    Z 1.8535 1.8538 0.0003
    DF 0.1042 0.0000 0.0000 0.1092 0.0050 0.0050 -------->
    TP RFS 0.0180 0.0000 0.0005 0.0000 #--------
    PR 1.6333 1.6338 0.0005
    PA 0.0121 -0.0392 -0.0513
    END OF DIMENSION LOC26

    Everything reports OK. But still not sure if this is what you had in mind.
Reply
  • I am using the terms float and fit interchangeably - sorry for switching terminology on you. The best-fit alignment you are using is doing rotation about Z axis, and translation in X and Y. You are not allowing the holes to "float" from datum B, because your best fit is not allowing translation in Z axis. To deal with this, add a 2nd best-fit alignment(recalling the first best fit alignment) and choose "Specified Constraints", then use the radio buttons to lock down all degrees of freedom except translation in Z axis. Thing is, I'm not sure this method is available in 3.7MR3. If it is not, then I would deal with it this way (after the first best fit alignment):
    - construct midpoint between the 2 holes at 3 o'clock
    - construct midpoint between the 2 holes at 6 o'clock
    - construct midpoint between the 2 holes at 9 o'clock
    - construct midpoint between the 2 holes at 12 o'clock
    - construct plane from the 4 midpoints
    - set Z origin on plane

    (v3.7MR3 doesn't seem to have the tools you mentioned, at least not in the Best Fit Alignment dialog box). So if Im understanding this correctly, I should make sure I've got my cursor inside the 2D-best-fit (the one I normally do), then create a new alignment and only change the Z origin with that alignment?

    Like this?
    set origin =ALIGNMENT/START,RECALL:2dBF_8Holes, LIST= YES
    ALIGNMENT/TRANS,ZAXIS,MPLN1
    ALIGNMENT/END

    Doing it that way, I got the following result...

    DIM LOC19= TRUE POSITION OF CIRCLE C1 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
    Z -1.8535 -1.8544 -0.0009
    PR 1.6336 1.6324 -0.0012
    PA -89.9870 -90.0082 -0.0212
    DF 0.1042 0.0000 0.0000 0.1084 0.0042 0.0042 -------->
    TP RFS 0.0180 0.0000 0.0033 0.0000 -#-------
    END OF DIMENSION LOC19
    DIM LOC20= TRUE POSITION OF CIRCLE C2 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
    Z 1.8535 1.8543 0.0009
    DF 0.1042 0.0000 0.0000 0.1072 0.0030 0.0030 -------->
    TP RFS 0.0180 0.0000 0.0017 0.0000 #--------
    PR 1.6336 1.6314 -0.0022
    PA -89.9878 -89.8944 0.0934
    END OF DIMENSION LOC20
    DIM LOC21= TRUE POSITION OF CIRCLE C3 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
    Z -1.8535 -1.8503 0.0032
    DF 0.1042 0.0000 0.0000 0.1058 0.0016 0.0016 -------->
    TP RFS 0.0180 0.0000 0.0064 0.0000 ---#-----
    PR 1.6337 1.6364 0.0028
    PA -179.9876 179.9900 -0.0224
    END OF DIMENSION LOC21
    DIM LOC22= TRUE POSITION OF CIRCLE C4 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
    Z 1.8535 1.8527 -0.0008
    DF 0.1042 0.0000 0.0000 0.1064 0.0022 0.0022 -------->
    TP RFS 0.0180 0.0000 0.0015 0.0000 #--------
    PR 1.6327 1.6299 -0.0028
    PA 179.9879 -179.9293 0.0828
    END OF DIMENSION LOC22
    DIM LOC23= TRUE POSITION OF CIRCLE C5 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
    Z -1.8535 -1.8522 0.0013
    DF 0.1042 0.0000 0.0000 0.1072 0.0030 0.0030 -------->
    TP RFS 0.0180 0.0000 0.0026 0.0000 -#-------
    PR 1.6334 1.6335 0.0001
    PA 90.0118 90.0412 0.0294
    END OF DIMENSION LOC23
    DIM LOC24= TRUE POSITION OF CIRCLE C6 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
    Z 1.8535 1.8542 0.0007
    DF 0.1042 0.0000 0.0000 0.1067 0.0025 0.0025 -------->
    TP RFS 0.0180 0.0000 0.0014 0.0000 #--------
    PR 1.6336 1.6339 0.0004
    PA 90.0120 89.9267 -0.0854
    END OF DIMENSION LOC24
    DIM LOC25= TRUE POSITION OF CIRCLE C7 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
    Z -1.8535 -1.8581 -0.0047
    DF 0.1042 0.0000 0.0000 0.1151 0.0109 0.0109 -------->
    TP RFS 0.0180 0.0000 0.0093 0.0000 ----#----
    PR 1.6336 1.6293 -0.0042
    PA 0.0120 -0.0130 -0.0250
    END OF DIMENSION LOC25
    DIM LOC26= TRUE POSITION OF CIRCLE C8 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
    Z 1.8535 1.8538 0.0003
    DF 0.1042 0.0000 0.0000 0.1092 0.0050 0.0050 -------->
    TP RFS 0.0180 0.0000 0.0005 0.0000 #--------
    PR 1.6333 1.6338 0.0005
    PA 0.0121 -0.0392 -0.0513
    END OF DIMENSION LOC26

    Everything reports OK. But still not sure if this is what you had in mind.
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