Need clarification of workflow with assemblies

sam_quintanar

Project background:
I purchased a 'diymore 2WD Smart Robot Car Chassis Kit' to learn a little about robotics and decided to simulate the robot before/during building it by using Onshape to create my robot model assembly  to support simulation in Webots.

onshape-to-robot software(https://onshape-to-robot.readthedocs.io/en/latest/ ) is being used to create a URDF file from an assembly that will be used with urdf2webots software(https://github.com/cyberbotics/urdf2webots ) to convert the URDF file to a PROTO file for use in webots.

If there is a more efficient way to go from an Onshape assembly to Webots, please chime in!

These are the steps taken to create a 2WD Smart Robot Car  assembly: (please point out better ways of doing things at any step)

1- Perused public documents & found what I needed & created an editable copy

2- The editable copy had an assembly, but no supporting sub-assemblies existed so I exported the assembly as PARASOLID and imported into a new document. This created all sub-assemblies & parts.

3- The newly imported assembly & sub-assemblies were without material assignments & mates/connectors. The onshape-to-robot software requires material assignments & mates/connectors to connect all parts to a 'root' base.

4- Made a copy of the assembly called 'Arduino Car Copy 1' to preserve original as I make modifications & deleted unnecessary sub-assemblies  https://cad.onshape.com/documents/d4a2496b8cc17c84bfc652c2/w/6f5a8ba8b99f0a3caed5feca/e/f47783f205d45f7af00acd30

5- Easily assigned materials to assembly & sub-assemblies

6- The task of connecting all parts to a 'root' base is where I currently am & is where I need further clarity. Is there a way to attach/connect all parts of the main assembly & sub-assemblies without having to break apart each sub-assembly to apply mate connectors? ; >>While at the same time declaring the motor axles, side wheels and caster wheel to be revolute without breaking them apart to apply mates? Placement of all sub-assemblies are already done, so it would be nice not to move them around. 

 i.e.- This motor sub-assembly https://cad.onshape.com/documents/d4a2496b8cc17c84bfc652c2/w/6f5a8ba8b99f0a3caed5feca/e/d3fade3ce844de5f303d7480  has all its parts disconnected & I want to connect everything, but have the axle revolute. Must I pull the axle out of the motor assembly to apply a mate connector, or is there a better way?   

wout_theelen541

I don't get everything in your post, when you make a post assume that the users answering will not have a technical background in what you're working on. If you need to explain something I assume that people won't open links instead explain your problem as concisely as possible use pics if you need to. With that being said I think I can provide some assistance. The first 1-5 steps sound fine. It doesn't matter if the parts have a Parasolid history or not the final model is the same. I would however try to keep things in OnShape in case you want to change your parts later on it's easier to do so with the history.

I am confused as to step 2 in that you say you didn't have subassemblies but then when you exported and imported the document you got subassemblies. Either you had subassemblies in the original exported files from Onshape or you manipulated the files after you exported. Either way it's sounds like it would be more logical to make the subassemblies in the original Onshape document to keep the Parasolid history as mentioned before. When you're in an assembly you should be able to right click on any other subassemblies or instances in the instance list and there should be an option to "move to new subassembly".

As for step 6 I am less familiar with the specifics as I haven't run any simulations yet but Onshape introduced Simulations only a short time ago. I don't think you will be able to run that on Onshape but you are doing everything else in terms of defining your materials and mates. There is a great webinar for that.
https://www.onshape.com/en/resource-center/videos/introducing-onshape-simulation
As for creating the mates without taking everything apart I would make use of section views and the isolate options.

I hope this helps if not feel free to ask some more.

wout_theelen541

I was just reading the Jan 11 updates and it seems that I was wrong. You might be able to use Simulation after all.
It might be handy to try this out first and make sure it works in OnShape. That way you can save time going back
and forth when you export to create your PROTO file.
https://forum.onshape.com/discussion/19873/improvements-to-onshape-january-11th-2023#latest
It would be interesting to compare the two simulation programs and see the results.

tim_hess

Hi @sam_quintanar, 

I think you're over-complicating thins a little bit here. I've never used Webots. However, I don't understand why you need to do steps 2, 3, and 4. Is it because the original document doesn't include the individual parts in part studios? If you have edit rights to the document, you should be able to directly add the sub-assemblies and mates that you need.

If you share a link to the document you're starting with, I think that would help others suggest a good workflow. 

Also, you don't have to create a copy to preserve anything. Onshape keeps a full history of all changes automatically. You can restore any previous version of a document at any time from the history tree. 

sam_quintanar

wout_theelen541   

Let me say first, that I greatly appreciate your input!

When I write of 'simulation' I'm referring to simulating the complete operation of my robot using 'Webots', not Onshape. Then I describe the tooling workflow to get from Onshape to Webots.

Your wrote: 'I am confused as to step 2 in that you say you didn't have sub-assemblies but then when you exported and imported the document you got sub-assemblies.' ---> Before exporting and importing, when I tried to export an individual part in the main assembly', I received a message saying the part did not exist or I didn't have permission to access the part. When looking at the left hand pane of the document listing all available sub-assemblies, some were there but most were not. After export and importing, 'all' sub-assemblies appeared and I was able to export individual parts from the main assembly. This is my experience using Onshape in this way.

When you write: 'As for creating the mates without taking everything apart I would make use of section views and the isolate options.', please recognize that such statements assume some advanced level of Onshape expertise. I am a Onshape novice, so if you could provide some links to what 'section views' and isolate options' are and how to use them, it would be great. They sound promising. Do you have readily available links?

sam_quintanar

@tim_hess
Thank you for your contribution!
Somehow, my replies/comments are not getting posted?! 

I already explained how I made a copy of the original document to edit it; so yes, I could edit it just fine, but if I tried to export any parts within the main assembly, a message would appear saying there was no permission to access the part or the part does not exist.

After doing steps 2 & 3 I was suddenly seeing sub-assemblies that were not available before and I could export individual parts without any messages telling me why it can't be done. I'm just reporting what happened.

I'm a novice at Onshape, so you are right that there is no need to make a copy of the original document to preserve it due to histories; but I was clueless on this aspect at the time.

tim_hess

Sounds like you're making some progress. You might want to check out the learning center, here: Course Catalog - Onshape Learning Center

There's a lot of stuff for people that are experienced with CAD, but new to Onshape. There's also a learning pathway for people that are new to CAD completely.