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Tertiary Datum doesn't constrain any degrees of freedom?

brian.freeman
2023.1--Selecting Datum A as a plane; Datum B as a hole, Datum C as a hole.
"GEOMAJIC" States Datum C doesn't control any degree of freedom
Without Datum C, Datum B doesn't constrain the final degree of rotational freedom.
Am I wrong here?
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  • If the vector of Dat B was EXACTLY perpendicular to Dat A then Dat C would control the rotation.

    Because Dat B isn't exactly perpendicular, PC-Dmis sees it as having some amount of inclination (relative to Dat A) which would control the rotation.

    PD-Dmis doesn't differentiate between if it was at 90° or 0.00001°.


    In alignment terms, Pc-Dmis is doing this:

    A_ABC =ALIGNMENT/START,RECALL:STARTUP,LIST=YES
    ALIGNMENT/LEVEL,YPLUS,PLN_A
    ALIGNMENT/ROTATE,ZPLUS,TO,CIR_B,ABOUT,YPLUS
    ALIGNMENT/TRANS,YAXIS,PLN_A
    ALIGNMENT/TRANS,XAXIS,CIR_B
    ALIGNMENT/TRANS,ZAXIS,CIR_B
    ALIGNMENT/END​

    Can, May, Must - because Dat B Can control the Rotation, and it May, then it Must!

    I asked previously but you didn't answer - are the Datums defined by Datum symbols (little triangle on the feature or leader lines) or by Datum Targets (A1, A2, A3, B1, B2 C1 etc)​
  • in reply to NinjaBadger
    Both--
    Datum A Targets
    Datum B Hole
    Datum C Hole
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