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Does Translating The Trihedron Ruin "True Zero"?

Bearpierro
Hello All!

I'm having a debate with a fellow programmer today on the effects of moving the trihedron away from the CAD's zero point.

This is in reference to a True Position measurement of a hole located at X0 Y14.5.


So there are two different methods to get our alignments and then dimension the true position:

Method 1
"Locate" The Part, by tapping a point on X, Translating the trihedron to that point, tapping a point on Y, Translating the trihedron to that point, etc for Z.

This obviously moves the trihedron around a bunch, and because of that physical features need to be used on the part to "return" the trihedron back to X0, Y0, Z0 on the drawing for the true position measurement to be taken.

Method 2
Leave the trihedron at X0, Y0, Z0 of the CAD model and NEVER translate it. Instead, tap points around the part and align without ever moving the trihedron.


Now, once dimensioned, both of these methods give me the same Nominal Measurement Values, X0, Y14.5.

Both of these methods use the same features to create their Iterative and Best Fit alignments.

Is there any difference in the end?

Please let me know if that wasn't clear enough, and thanks in advance for any help!
Parents
  • Your initial alignment locks the part down from moving, so anything you do after is moving around the part, don’t be fooled by being able to move the CAD model virtually, your program represents the mating part or parts. So you can move your trihedran around, and the part never moves. Even when using Xactmeasure or Geo Tolerances, if your alignment isn’t the same as your Datum structure, if you put your cursor on that callout, you’ll see a temporary trihedron on the screen. Technically your moving the mating part around when changing the coordinates of the trihehdron

    I may need you to dumb this down for me. If I'm reading this correctly it means that movement is happening regardless when we make alignments throughout the program, so it shouldn't make a difference which method is used?

    For some added clarity, both methods are using a READ POINT alignment to establish the initial zero on the part.
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  • Your initial alignment locks the part down from moving, so anything you do after is moving around the part, don’t be fooled by being able to move the CAD model virtually, your program represents the mating part or parts. So you can move your trihedran around, and the part never moves. Even when using Xactmeasure or Geo Tolerances, if your alignment isn’t the same as your Datum structure, if you put your cursor on that callout, you’ll see a temporary trihedron on the screen. Technically your moving the mating part around when changing the coordinates of the trihehdron

    I may need you to dumb this down for me. If I'm reading this correctly it means that movement is happening regardless when we make alignments throughout the program, so it shouldn't make a difference which method is used?

    For some added clarity, both methods are using a READ POINT alignment to establish the initial zero on the part.
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