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Alignment from FCF Datum Shift



I think what vpt (and me) were hoping for was a way to create an alignment that uses the Xact fit shift. There are all sorts of applications for this. Using the available options in best-fit alignment is not the same, because they do not attempt to fit within a tolerance zone.

A few years old but I haven't found anything using search.

SPH1       =GENERIC/SPHERE,DEPENDENT,CARTESIAN,OUT,$
            NOM/XYZ,<0,0,0>,$
            MEAS/XYZ,<0,0,0>,$
            NOM/IJK,<0,0,1>,$
            MEAS/IJK,<0,0,1>,$
            DIAMETER/1,1.1
DIM LOC1= LOCATION OF SPHERE SPH1
AX    NOMINAL       +TOL       -TOL       MEAS        DEV     OUTTOL
D       1.0000     0.2500    -0.2500     1.1000     0.1000     0.0000 ------#--
END OF DIMENSION LOC1
            DATDEF/FEATURE=SPH1,A
            DISPLAYPRECISION/6
FCFLOC1 =POSITION : CIR152_1,CIR152_2,CIR152_3,...
            FEATCTRLFRAME/SHOWNOMS=NO,SHOWPARAMS=NO,SHOWEXPANDED=NO
              SIZE TOLERANCES/33,DIAMETER,0.375,0.005,-0.005
              PRIMARY DIMENSION/POSITION,DIAMETER,0.01,MMC,A,MMC,,
              NOTE/FCFLOC1
            FEATURES/CIR152_1,CIR152_2,CIR152_3,CIR152_4,CIR152_5,
                                CIR152_6,CIR152_7,CIR152_8,CIR152_9,CIR152_10,
                                CIR152_11,CIR152_12,CIR152_13,CIR152_14,
                                CIR152_15,CIR152_16,CIR152_17,CIR152_18,
                                CIR152_19,CIR152_20,CIR152_21,CIR152_22,
                                CIR152_23,CIR152_24,CIR152_25,CIR152_26,
                                CIR152_27,CIR152_28,CIR152_29,CIR152_30,
                                CIR152_31,CIR152_32,CIR152_33,,
            ASSIGN/V1=GETTEXT("DRF_SHIFTX",1,{FCFLOC1})
            ASSIGN/V2=GETTEXT("DRF_SHIFTY",1,{FCFLOC1})
            ASSIGN/V3=GETTEXT("DRF_SHIFTZ",1,{FCFLOC1})
            ASSIGN/V4=GETTEXT("DRF_ROTATIONX",1,{FCFLOC1})*-1
            ASSIGN/V5=GETTEXT("DRF_ROTATIONY",1,{FCFLOC1})*-1
            ASSIGN/V6=GETTEXT("DRF_ROTATIONZ",1,{FCFLOC1})*-1
            FORMAT/TEXT, , ,HEADINGS, , ;NOM,MEAS, , , , , 
DIM BEFORE= LOCATION OF CIRCLE CIR152_1
AX     NOMINAL        MEAS
X     10.153721   10.154507
Y    -27.402826  -27.405035
Z     -8.032519   -8.025360
END OF DIMENSION BEFORE
ALIGN1     =ALIGNMENT/START,RECALL:PREVIOUS,LIST=YES
              ALIGNMENT/ROTATE_OFFSET,V4,ABOUT,XPLUS
              ALIGNMENT/ROTATE_OFFSET,V5,ABOUT,YPLUS
              ALIGNMENT/ROTATE_OFFSET,V6,ABOUT,ZPLUS
              ALIGNMENT/TRANS_OFFSET,XAXIS,V1
              ALIGNMENT/TRANS_OFFSET,YAXIS,V2
              ALIGNMENT/TRANS_OFFSET,ZAXIS,V3
            ALIGNMENT/END
DIM AFTER= LOCATION OF CIRCLE CIR152_1
AX     NOMINAL        MEAS
X     10.151373   10.152161
Y    -27.394485  -27.396694
Z     -8.041472   -8.034312
D      0.376500    0.377383
END OF DIMENSION AFTER
            COMMENT/REPT,
            "Xshift:  "+V1
            "Yshift:  "+V2
            "Zshift:  "+V3
            "Rotation X:  "+V4*-1
            "Rotation Y:  "+V5*-1
            "Rotation Z:  "+V6*-1

The FCF output with datum shift is:


Using a sphere as the only datum seems to allow all 6 degrees to float. There is some small round-off error due to the numbers being used limited to the current DISPLAYPRECISION (not much).

Now what? Trying to actually use this has me baffled. I'd like to simulate the FCF output having the transformed measured coordinates evaluated against the model nominal values. The BEFORE dim has the nominals I want but the AFTER dim has the measured I want (like the FCF output). Inserting & Recalling alignments, Updating Dependent Commands (answering both yes and no) leaves me feeling like I've found my way into a rabbit hole. Maybe Profile dims behave differently?

I'm aware that some settings may influence the results: Update Dependent Commands (warning), UpdateBelowChangedAlignmentDuringExecution (registry), Ignore CAD to part (F5 settings), Allow Fine Tuning of Alignment (F5 settings). I'd really like to get this working inline without resorting to any type of external automation if possible. Can someone throw me a bone here? There's gotta be a way to get some mileage out of this.
Parents
  • Shouldn't you do trans_offset before rotate_offset?

    Thinking about it, we don't know the order it was done in the FCF, and if it's done in the order the standard dictates, we have to decode the datums to know it...

    Or am I completely out on a limb here?

    I agree with you anders.

    The xyz ijk offsets aren't a sequence as such they're a final result - I think you'd have to do xyz first then ijk.

    Both of you are right. The translation should come first (per AndersI example) then the rotations. I was hasty in attributing the small "round off" error of millionths I saw to the precision being worked to. Following AndersI's sequence left me with absolutely no difference at all. Thanks to both of you for clearing that up!
Reply
  • Shouldn't you do trans_offset before rotate_offset?

    Thinking about it, we don't know the order it was done in the FCF, and if it's done in the order the standard dictates, we have to decode the datums to know it...

    Or am I completely out on a limb here?

    I agree with you anders.

    The xyz ijk offsets aren't a sequence as such they're a final result - I think you'd have to do xyz first then ijk.

    Both of you are right. The translation should come first (per AndersI example) then the rotations. I was hasty in attributing the small "round off" error of millionths I saw to the precision being worked to. Following AndersI's sequence left me with absolutely no difference at all. Thanks to both of you for clearing that up!
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