Part Alignment and Datum Setup

[[Do...]]

I have this part that I am unsure as to how I should setup my alignment and datum structures. My part is initially leveled to datum A, and then my origin is datum B which is a through hole and then datum C (which is a plane) is used to align the part or set the rotation. Can someone please advise as to what the best practice would be for setting this up. I have provided a crude image of what the part looks like and where the datums are.

Screenshot 2021-11-04 164747.jpg

[[Pa...]]

On my opinions,Drawing is just drawing,more important is what is the usage of this component. 😃

[[Do...]]

It is a pedal. The part is nested up against datum A with a shaft through B. Datum C is a pad that activates a switch when the pedal is pressed down.

[[To...]]

I might consider using other features that are larger and more stable for the base alignment. Then, use A, B & C in the characteristics. Using ABC for Primary, Secondary and Tertiary will create a new coordinate system but will likely be more repeatable due to using BA that is more stable and robust.


Also, if you do this, avoid looking at the features for location information because it WILL be different. If you do the above, I suppose you could create a secondary alignment using ABC and assign it to the rest of the features but you'll need to make sure evaluation settings are the same as the ABC reference frame, i.e. outer tangential, constraints per ISO 5459.

[[Do...]]

How would you incorporate C in the secondary alignment? It is an angled plane and would cause your secondary WCS to rotate.

[[Ro...]]

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Hi Donny,
As it should. If you want to report the results to a different orientation, use the "Special" button in the alignment after aligning to A-B-C and rotate a basic angle to your desired orientation for reporting dimensions.

[[Ow...]]

Here is a good video link showing how to use the special rotations with examples.
https://www.youtube.com/watch?v=rZJ50rd4gjg

[[Ow...]]

A document that might help if you don't have good enough internet to support videos.

[[Do...]]

Thank you. Both the video and the document were helpful.

[[Ma...]]

One thing to bear in mind regarding all alignments including the base alignment is that elements with an axis are zeroed at the point they intersect with the other reference axes. So in this case, if A is the primary in the alignment and B is measured as a cylinder B will be zero where it intersects plane A rather than at the middle of the B axis. In most cases this isn't very significant but if the two features are significantly out of square and/or long projections are involved it can become significant. This can be worked around by intersecting B with a theoretical plane at mid-depth and using this intersection as the B datum in the alignment.