Assembly Mates with Subassemblies are driving me crazy - what am I doing wrong??

dave_franchino

Hey folks,

I'm sorry but working with Assembly mates in Onshape is driving me crazy. Here is my current problem. I'm trying to assemble a subassembly into an upper level assembly. Because my subassembly is, in turn, made up of it's own subassemblies, when I bring it in and add a mate it is only moving part of the subassembly - not the entire thing. Never made any sense to me but I've been told I need to "group" the assembly before moving. However when I try to group that subassembly I am getting an error: Group 1 has error: Mate cannot be added between members of the same group (hidden). I have no idea what this means. How do I fix this??? I just want to put a subassembly into a higher level assembly and mate it. Shouldn't be that hard.

I continue to struggle with:

Why don't we have access the planes in an assembly. That makes it really hard to assemble in many real-word situations.
Why isn't the "default" bringing in a subassembly as a group. Isn't that the whole point of an assembly?

I know smart people created this system but a search online appears to show a lot of people struggling with these same issues. I'm wondering if Onshape outsmarted itself here.

I do like Onshapes in-context design but I really struggle to effectively use assemblies and it's getting pretty tiring. What am I missing here?

S1mon

It does take time to get used to, coming from Creo or Solidworks (my frames of reference), but ultimately, I'm pretty happy with it now (minus a few things that continue to drive me crazy - like not being able to start a cross section of swoopy parts in an assembly).

Try some of these threads:

https://forum.onshape.com/discussion/comment/91998#Comment_91998

https://forum.onshape.com/discussion/23472/using-fix-rather-than-mates

https://forum.onshape.com/discussion/15459/placing-mate-connector-on-origin-or-on-planes

jelte_steur814

Hi Dave,

Just stick with it, once you'll get the hang of it, it's really not that hard.

A sub assembly that is not fully constrained to itself, will also not be when loaded into a parrent assembly. It will remain loose.
when the subassembly is in the correct position internally, create that group IN the subassembly level.

the only thing that changes from the subassembly when loaded into the parent is the fix. so in the subassembly, feel free to fix one part, group the rest to it and see in the part tree that all parts are now no longer movable.

then within the parent assembly, the subassembly will behave as one fixed group of parts.

@S1mon : completely agree with your cross section issue. I sometimes load this part into the assembly and fix it to the origin:

feel free to use it..

Now with configurable size…

Origin cube for section cuts

S1mon

@jelte_steur814

That's an interesting work around.

rick_randall

@jelte_steur814 This is one I have got to remember. Thanks

MDesign

Ha I just used the cube method earlier this morning to do sections to inspect some assembly of stl meshes. Works great. Was looking for a way to create planes in assembly but I guess that confirms it wasn't possible.

rick_randall

@dave_franchino - Getting back to your original question, are you aware that groups and mates don't mix well together? The problem occurs if you try to group parts that already have mates, this condition will always throw a red flag(s) - to correct this, you can delete or suppress the mates, or make your groups first, then mate the groups together afterwards. It's an "order of operation" kind of issue - and, only group parts that will act as one single unit (think of a group as a single part), and don't group anything that will move later, relative to other parts in the same group. Once you wrap your head around how this works, it's a pretty straight forward concept.

eric_pesty

Also note that you now have the ability to "lock" a sub-assembly so that it's components are all grouped together, which is a better way of doing this than using a group mate!
It also lest you leverage any "named positions" defined in the sub-assembly.

dave_franchino

Thanks for the helpful suggestions. One common issue I could use a bit of advice on. It's pretty common for me to bring in ball bearings or other standard "assemblies" from McMaster Carr - I'm assuming I'm not unique in doing this.

When I import a ball bearing it shows up as a part studio with a whole bunch of parts. If I want to use this in an assembly what is the best way to do so?

I could create a subassembly, insert all these parts, rebuild mates and then put this into my assembly but that feels like a lot of work.

On a few of their downloaded "parts" containing multiple parts I can add a boolean union to essentially combine everything into one part but that doesn't always work - for example on ball bearings they balls don't actually touch or intersect in a way that allows the boolean to work.

I have taken to just inserting the McMaster part studio into my assembly and "grouping" it but my model tree it getting really long and confusing with tons of "part1, part2, part3, etc.

What's the best way to handle this common scenario if grouping and mating don't play well together?

Thanks!!!

eric_pesty

Composite part…

rick_randall

@dave_franchino - partial quote …

"I have taken to just inserting the McMaster part studio into my assembly and "grouping" it but my model tree it getting really long and confusing with tons of "part1, part2, part3, etc."

Once you make that composite part that Eric said - rename it. Do yourself a favor, and get into the habit of renaming all your parts (and features for that matter). The names don't have to be very long (the shorter the better actually) but something meaningful, that will make sense to you in the future. This may seem like it takes extra time, but is especially important, when it comes time to edit parts or sketches later on.