Export multiple parts as a single file using Onshape's assembly export feature

Onshape lets you combine multiple parts into one downloadable file through the assembly export tool. The process depends on whether your parts are already grouped in an assembly — if they are, you can export directly; if they're separate, you'll need to create an assembly first, then export it as a single STEP, IGES, or STL file.

The most common reason to do this is to send a complete design to a manufacturer, 3D printer, or colleague without forcing them to manage multiple files. A single exported file is also easier to version-control and archive.

Key Takeaways

  • Parts must be grouped in an assembly before you can export them as one file; exporting individual parts separately will give you multiple files instead.
  • Create an assembly by inserting your parts into a new assembly document, which takes about two minutes and requires no special permissions.
  • Use the export button in the assembly view, then choose STEP format for most manufacturing work or STL for 3D printing.
  • The exported file will contain all parts in their relative positions, so moving parts in the assembly before export changes what the recipient receives.

Creating an assembly if your parts are separate

If your parts live in separate Onshape documents or tabs, you need to group them in an assembly first. Open a new document in Onshape, click the Create button, and select Assembly. This opens a blank assembly workspace.

In the assembly, click Insert and choose Part Studio or Assembly. Navigate to each part you want to include and insert them one at a time. Onshape will place each part at the origin; you can move them into position using the Move or Mate tools if you need them aligned a certain way. If the parts don't need to be positioned relative to each other, you can leave them as-is and export when ready.

Exporting the assembly as a single file

Once all parts are in the assembly, click the Export button in the top right of the assembly view. A menu will appear asking you to choose a file format. STEP is the standard choice for most work — it preserves part boundaries and is readable by nearly every CAD program and manufacturing software. IGES is older but still widely supported. STL is for 3D printing and converts everything to a mesh, losing the original part structure.

Select your format, choose a filename, and click Export. Onshape will read a single file containing all parts in their current positions within the assembly. The file size depends on part complexity, but typically ranges from a few hundred kilobytes to several megabytes.

What happens to part relationships when you export

When you export an assembly as STEP or IGES, Onshape preserves the individual part bodies and their spatial relationships. This means the recipient can open the file in their CAD software and see each part as a separate solid, not as one merged object. They can select, measure, and modify individual parts if needed.

If you export as STL, all parts merge into a single mesh with no internal boundaries. This is fine for 3D printing but makes it impossible to edit individual parts afterward. Use STL only if the recipient explicitly needs it for a printer or visualization tool.

Positioning parts before export matters

The positions of parts in your assembly are baked into the exported file. If you move a part in the assembly view after inserting it, that new position is what the recipient will see when they open the exported file. Double-check that parts are where you want them before exporting — moving them after export requires the recipient to reposition manually.

If you're exporting parts that don't need to be positioned relative to each other (for example, identical brackets being sent to a supplier), you can leave them at the origin. The recipient will understand they're separate parts and position them as needed for their own work.

Sharing the exported file with others

Once exported, the file is a standard CAD document that works in any software that reads STEP or IGES — Fusion 360, FreeCAD, SolidWorks, AutoCAD, and most manufacturing software. You can email it, upload it to a shared drive, or use a file-sharing service. The recipient doesn't need an Onshape account to open it.

If you need to make changes later, edit the parts in Onshape and export again. The exported file is a snapshot; changes to the Onshape document don't automatically update files you've already sent out.

Troubleshooting common export problems

If the export button is grayed out, you're likely viewing a Part Studio instead of an Assembly. Switch to the assembly tab or create a new assembly and insert your parts into it. If the file size is unexpectedly large, check whether you've accidentally inserted the same part multiple times or included geometry you didn't intend to.

If the recipient reports that parts are missing or in the wrong position, verify that all parts were inserted into the assembly and that you exported from the assembly view, not from individual Part Studio tabs. Parts in separate tabs will not be included in the export unless they're explicitly inserted into the assembly.

Frequently Asked Questions

Can I export parts without creating an assembly?

No. Onshape's export feature works only from assembly documents. If you try to export from a Part Studio, you'll get only that single part. Creating an assembly takes two minutes and is the only way to combine multiple parts into one file.

What format should I use if I don't know what the recipient needs?

STEP is the safest choice. It's the industry standard, works in nearly every CAD program and manufacturing tool, and preserves part structure. Ask the recipient if they have a preference, but STEP will work for almost any use case.

If I export as STEP, can the recipient edit individual parts?

Yes. STEP preserves each part as a separate solid body, so the recipient can select, modify, and measure individual parts in their CAD software. They cannot edit the parts as parametric features (like changing a hole diameter), but they can move, delete, or measure them.

Does exporting use up my Onshape storage or document limit?

No. Exporting creates a file on your computer or in your read folder. It doesn't consume Onshape storage or count against any document limits. You can export the same assembly as many times as you want.

What if parts are mated together in the assembly — does that affect the export?

Mates control how parts move relative to each other in Onshape, but they don't merge the parts or change the export. The exported file contains all parts in their current positions, with no mating information. The recipient receives separate solid bodies that they can move freely in their own software.