Mirroring an assemby

I’m a mentor trying to learn Onshape before we start training new students with it.

I made an assembly that is the entire right side of a robot base, with structural elements, motors, mecanum wheels, shafts, odometry, etc. I want to mirror the entire assembly to create a left side so I don’t have to literally duplicate all the work I did making the right half.

Is there a mirror function for assemblies yet?

if not, is there a solution that doesn’t involve doubling all my work?

From what I have found, no.
The best workarounds seem to be a circular pattern, although that only works if your things are symetrical or you don’t care.
You may need to strip the assembly back a bit to do this properly.


No mirroring of assemblies in Onshape is an old complaint (and still no sign of it showing up). As stated above, the best bet is to do an assembly circular pattern about some axis in the center of the robot (may need to add this).



It’a a left/right mirror. Circular won’t work. How can people work without mirror?

1 Like

The best option is to mirror parts at the Part Studio level. The Part Studio makes it easy to model all of the parts in-place, so a typical workflow is to model half, mirror in the Part Studio, and then drop that into the assembly. A group mate can then keep all components locked in relation to each other. When you’re adding in your bearings or other COTs parts, you can use the Replicate feature to handle the repetitive placements for you.

Here’s a link to a robot that shows off this process - the intake is pretty simple, but shows how to make the most of the group mate and modeling in-place to make the assembly process a lot simpler.

a lot of the things I want to mirror are step parts that I am importing directly into the assembly. I’ve built the right half the robot out of those parts. I haven’t actually drawn anything, so I don’t have the option to mirror.

do I need to go in to each file and make a left hand version of the parts that need unique L/R versions?

This is a very standard complaint and it’s one of the many things that everyone that moves from solidworks and inventor/fusion into OnShape thinks is a very big deal.

That being said, now that I have used OnShape for 3 years I rarely miss assembly mirror.

Part Studio Mirror Process
On occasion when I need multiple left handed parts (sheet metal parts mostly) I will

  1. Create a new part studio
  2. Derive in the parts from the other part studio I want to mirror
  3. Do a mirror feature for all those parts across my mirror plane.
  4. Delete the derived parts (delete part is a feature in OnShape and can use as part of your design process).
  5. Rename the new parts to “Mirror-”

Assembly Mirrors
As for assembly mirrors you can learn some tips to make making the other side faster.

  • you can build up your subassemblies so that you don’t need to mirror them and can just insert them where needed.
  • Mating is so fast in OnShape with groups and the one mate per object flow that you can very quickly build two different mirrored sides of an assembly in just a few clicks.
  • The replicate feature can help quickly insert some parts (fasteners, bearings, etc).
  • You can create mate connectors and insert sketches into your assembly to help you properly locate parts in space.

This has the advantage of making sure you absolutely know and are intentional about creating left-handed parts. We used to have students do it on accident and not realized their parts needed more work to be symmetric.

The OnShape design process is slightly different than other traditional CAD packages but if you lean into it, you eventually learn to love it. I dread the times I have to go back to solidworks or inventor/fusion now that I’m accustomed to OnShape’s process.


Thanks for the step by step. I’m coming from a very different world, almost 20 years of sketchup for architecture and design, and about 5 years of catia v3 for a car company. We only ever modeled half the car because the other half was 99% redundant, then we could mirror the whole thing with one click. We dont have any onshape knowledge on our team, and trying to fumble my way through the functionality i never used (sketch/parts/assemblies) has been frustrating without having someone i can just ask when i hit an issue. Thanks though.


what feels daunting here is that if I go through all of these steps to create the right half of the robot, then if we change something major like the side rail which the motors, wheels, odometry, etc are mated to, we now have to re-mate everything twice, for right and left. maybe there’s something i’m missing because there’s nobody to teach me, and finding a tutorial for the exact issue I’m facing is hard. I found some tutorials for replicate, but some were way too advanced and i didn’t even know where to start, and others showed the steps simply, but they just didn’t work when I tried (click on a part that has a mate, but the replicate window doesn’t autopopulate the mate).

what do you think is the best approach for me (and other mentors and students) to learn how to use onshape efficiently for first?

I’d recommend watching this workshop from OnShape, they interviewed multiple teams before it to show examples of how to use OnShape to design FRC robots.

As you do more, more parts can be made in your part studios using features scripts (any extrusion/tube) and those can be easily mirrored in the part studio.


thanks, I’ll take a look. i appreciate the help.