Challenges with Origins, Mate Connectors, and Imported Assemblies

S1mon

If I import an assembly (call it 'A'), and its origin is not located on a part feature, but yet I want to use the origin as a mate reference in another assembly (call it 'B'), what is the best way to do this?
(this happens to be a PCBA that I can't share)

Steps

1. Import a STEP from Allegro for a PCBA
2. fix one part in assembly A (a connector or some other unlikely to change part)
3. group all the parts in assembly A
4. add a mate connector (call it 'C') at the origin of A
5. create a mate connector in B (call it 'D')
6. insert A into B and use a fasten mate between 'C' and 'D'
7. drag parts of A around in B
8. C and D stay locked together, but because the fix from #1 goes away in B, C just floats relative to the parts from A

It seems like there's probably a better way to do step #3 so that the mate connector is tied to the parts, but since there's no feature at the origin, it's awkward. I can create a mate connector which is manually offset from some part feature, but if there's a good chance it won't be a round number, and then I can't be sure that my assembly positions will match the other CAD system. This seems like madness when all I want is a reference at 0,0,0 that doesn't float around.

I'm slowing wrapping my head around how the mates in Onshape work but decades of Pro/E and Solidworks are making this confusing. Especially since so many things that I work on are assembled and don't have a lot of motion. I'm used to dropping in an assembly at a default position and having it not move.

sebastien_frys

Hi Simon,
I have a very similar issue.
Did you find a solution?

S1mon

I can't remember exactly how I ended up dealing with this. I think I might have manually created a mate connector in a part studio using offsets to put the MC out in space at the 0,0,0. I don't remember there being a great solution.

romeograham

I use this Custom FeatureScript "Mate Connector at Origin" (by @Jake_Rosenfeld at Onshape) for this: https://cad.onshape.com/documents/7a2aca223858e21747087f1c/v/d06b9de45deb6bba4211204a/e/36a983633c3f3c601fd50add

It creates Mate Connectors (one for each part you select) at the Origin, with Z aligned with Z.

Great for positioning parts later in the assembly.

Though - you'd need to ensure that your original import put all the bodies in their correct positions in the Part Studio (rather than putting them all at the origin).

S1mon

@romeograham

I remember reading about this FeatureScript before. Now I've added it to our toolbar.

(BTW. Your link has an enterprise account in the URL.)

romeograham

Thanks @S1mon - interesting - that's the original FS that I linked to...not an internal copy or anything. I think it builds the URL that way because I'm logged into my Enterprise account - not to cad.onshape.com.

I'm guessing that when you click that link above, the URL that you go to is either cad.onshape, or your enterprise account. Is that the case?

S1mon

When I click that link, I get an error because I don't have permission to log into your enterprise. If I edit it to replace "jps" with "cad" then it works.

romeograham

OK - thanks. I edited the URL to fix that for others. Haven't run into this before when I paste URLs.