Splitting part after assembly - is it possible to relink mates?

grzegorz_zdanowski

I think my problem is relatively simple problem. Example document: https://cad.onshape.com/documents/e54a188f695469ab600fefe5/w/7ea27d683f3bb7e915a1367e/e/d5536f4b1cbde0ee22c8b95a

As you can see there's a simple assembly, consisting of 4 rods and some case/block where they can slide:



Now, lets say I want to e.g. use FDM and need to split the case part like so:



As I expected, this naturally breaks the assembly process as the original non-split part doesn't exist in the Parts Studio:



OnShape allows replacing the part with new one and it will restore all mates. However, there's an interesting head-scratcher: you cannot replace one part with two (i.e. a split one). I can insert two of them back and relink one but it will only relink a [small] subset of mates which are present on that fragment of the part:



One workaround I found is creating a composite part in Parts Studio and replacing with the composite. However, this solution is also flawed: doing makes it impossible to do assembly of split parts (as the Assembly Studio gets a single logical entity - the composite part).
Is there something I'm doing wrong here?

rick_randall

You might try this - Edit your slider mates, so that you use the midpoint of the hole in the case (there will always be a midpoint, even if you edit the case), instead of using the ends of the holes.  I have not tried this, but I think it could work.

good luck

nick_papageorge073

That is the nature of CAD. If you make major changes, expect to rebuild a few things.

You could put in mate connectors after the split in the part studio, and have them all owned by the right-side part. Then mate the cylinders to the mate connectors in the assembly. You would have still had to redo your mates, however, unless you had pre-planned to do that.

grzegorz_zdanowski

rick_randall said:

You might try this - Edit your slider mates, so that you use the midpoint of the hole in the case (there will always be a midpoint, even if you edit the case), instead of using the ends of the holes.  I have not tried this, but I think it could work.

good luck

I don't think this will work. The major problem is OnShape is losing reference to the part and the new state contains two parts rather than one.

nick_papageorge073 said:

That is the nature of CAD. If you make major changes, expect to rebuild a few things. (...)

Coming from software engineering background, this is understandable. However, I think I'm missing an option like "relink all selected to this part" - I don't have a problem hinting CAD that mates just moved somewhere else, this is logical. However, the only option I see is to replace missing part with new one (in which case all mates are linked back as they were), and then manually re-do mating of all other parts for the other side of the split. While in this case with 5 parts total it's easy, doing this with 50+ parts is going to be tedious to say the least

nick_papageorge073 said:

(...)
You could put in mate connectors after the split in the part studio, and have them all owned by the right-side part. Then mate the cylinders to the mate connectors in the assembly. You would have still had to redo your mates, however, unless you had pre-planned to do that.

So what you're saying, I should define manual mate connectors in the parts studio(s) for every part, and then use these mate points in assembly to quickly re-do mating if a major change like split of a big part happens? While this will not help me a lot here saving time, it will be a great lesson for the future if this is the case
I guess the magic auto-creation of mates bit me here then.

eric_pesty

Another option would be to create a "helper surface composite part" that includes all the "hole ends" before you do the split, then insert that and "fix" in you assembly. Then you can mate your cylinders to that and then the other part that is either one or multiple can be either manually mated to that helper surface or possibly even just "grouped" with the surface.

https://cad.onshape.com/documents/cfc51e9ec1a584a29cd7e254/w/5e19cec11feaa5a72e38acd6/e/5e71e4e2d5c67471812f6dfb