Does Translating The Trihedron Ruin "True Zero"?

Unless we are inspecting in plane or car locations, the model is often not in the same place in a CMM or on installation as when it was drawn.

And, so far as I know, machines aren't capable of machining in those coordinates, they zero on a vice, or a tooling ball, or the corner of a block of metal. The CNC machine never (that I've ever witnessed) picks up G54 at the part's A-B-C zero.

When the model is drawn, it isn't drawn in A-B-C zero coordinates. It is drawn off planes that are created all over the place, often incrementally, and the solid is added to and cut away.
That is then mated into an assembly and run through some analysis (for structural stuff at least).
THEN it is isolated back out and a drawing is made. That drawing probably has very limited tie-in to the way it was drawn.

We draw perfect.
The print is to let us make it imperfect while still working and controlling cost.

You can import the model, take hits in probe mode, make the alignment and then run that, which will spin the part to match the way it is sitting in the machine
-or-
you can import the model, translate it so it is like in the machine and move the zero where you want it to make it easier on the guy to load the part so it looks like the screen
-or-
you can manipulate the part in some cad system and export it with those coordinates and leave it like that.

Does not matter in any way, shape or form.

Closest you get to an issue is with translating the model from its native CAD creation, and that is usually very minimal, other than the odd fillet radius trimming backwards.

If I now understand what you are asking. Nothing you do with translation has any effect on the model's coordinates system for any features in the model.

I have never seen a probe be placed perfectly to a readpoint position. We have always used multiple translations prior to starting to measure the actual datum features. I'm not sure what your coworker's thought is, but I feel I'm missing something in these explanations.
At the end of it all, as long as you are aligning to your datums as described by your print, you shouldn't have any issues with your 0 point. And the measured 0 point is more important than the CAD 0 point, imo.

I agree with everything you're saying 100%. My coworker's argument is that if the trihedron doesn't move from the zero point on the drawing when it is imported, and he just creates features and Best Fit aligns to them then that origin point will be "perfect". My argument would be that it's a theoretical origin point with no real tie to the physical part itself.

I appreciate everyone's input on this. It's a difficult problem to explain but I think I've gotten some valuable responses here.
As far as I know the only way to tell if my "origin" point is correct is that when I dimension true positions my nominal values should be accurate to the drawing, which they are.

I agree with R2ah1ze1l,
Maybe I'm missing something important but I also feel your co-worker has been told or made to believe something in the past and is unwilling to see it any other way.
My origin is almost always somewhere other than the original cad origin. Align to the datum structure and dimension away. Never had a problem...

I appreciate everyone's input on this. It's a difficult problem to explain but I think I've gotten some valuable responses here.
As far as I know the only way to tell if my "origin" point is correct is that when I dimension true positions my nominal values should be accurate to the drawing, which they are.

then you have no issue. let your co-worker program the way he wants, and you go your own way. I have found over the years of programming I have done, there are MANY ways to achieve the end result. I have worked with programmers that create programs I can immediately understand their thought patterns, and one I totally don't get. as they say, "there's a 100 ways to skin a cat", its the results that matter.

9* ways to skin a cat. Cats have 9 lives after all

That's about where we've landed. I'm going to continue doing what I was taught in training, it hasn't failed me yet!

I've always asked whoever is trying to feed me a line of BS to show me. Most of the time they have to back off and once in a great while I learn something.

If the cad model is built to the drawing sometimes they will use other co-ordinate systems i.e. Wing system instead of part and they will build from there and then rotate to a part system after. This means in catia a hole might be X 14.00453 Y 20.00764 Z 10.000. but the drawing will only be to 2 decimal places. Therefore if you translate to said hole and then offset back drawing values as round number ( X14, Y20, Z10. you wont end up at the exact original co-ordinate and could put errors into rotations or other features. drawings are very commonly rounded up decimal places. In reality you need either the original 3d data or tabulation data i.e. Anvil,Cadd5,catia ect.