best fit and true pos

Hello,
Very new to the romer and pc-dmis...
I aligned my part with a Plane, Circle and Circle. Defined the datums A, B & C. Did a True Pos to A B & C to a bunch of holes.
Now I insert a new alignment Best Fit to 3 of the circles. I do the True Pos dimension again and get the exact same results..? When switching between the two alignments I do see everything shift a tiny bit. Should the True Pos results change or do they stay the same as the relationship between datums AB&C to the holes is still the same?
thanks,
eric

Colin Simithraaratchy over 12 years ago

Hello,
Very new to the romer and pc-dmis...
I aligned my part with a Plane, Circle and Circle. Defined the datums A, B & C. Did a True Pos to A B & C to a bunch of holes.
Now I insert a new alignment Best Fit to 3 of the circles. I do the True Pos dimension again and get the exact same results..? When switching between the two alignments I do see everything shift a tiny bit. Should the True Pos results change or do they stay the same as the relationship between datums AB&C to the holes is still the same?
thanks,
eric

If you're using an FCF true position:

PCDMIS creates a temporary alignment to the ABC datum ref frame. It even displays it: when you have your cursor on the FCFTruePos in the Edit Window, you should see a blue/yellow XYZ trihedron show up. In your case, since you aligned to ABC, the blue/yellow trihedron and traditional red/green trihedron will be superimposed atop one another.

Basically, the FCF retains the ABC alignment despite your Best Fit alignment.
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