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

Onshape lets you export all parts from a document as one combined file in several formats, but the method depends on whether your parts are in an assembly or scattered across a document. The fastest route is to create an assembly that contains all your parts, then export that assembly as a single STEP, IGES, or STL file. If your parts are already in an assembly, you can export directly without extra steps. If they're loose in your document, you'll need to add them to an assembly first — this takes a few minutes and doesn't change your original parts.

The exported file merges all part geometry into one solid body, not separate components you can move independently. This is useful when you're sending designs to a manufacturer, preparing files for 3D printing, or sharing a complete assembly with someone who doesn't need to modify individual parts.

Key Takeaways

  • Parts must be inside an assembly to export as one combined file; loose parts in a document cannot be merged into a single export.
  • Create a new assembly, drag all your parts into it from the left panel, and Onshape will position them at their original locations.
  • Right-click the assembly name and select Export to choose your file format (STEP is most compatible, STL works for 3D printing).
  • The exported file contains all part geometry merged into one solid, not separate bodies — check the result in your CAD software before sending to manufacturing or printing.

Creating an assembly from loose parts

If your parts live as separate sketches or part studios in your document, you need an assembly to hold them. Open your Onshape document and look at the left panel where your document tree appears. Click the plus icon next to "Assemblies" and select "New assembly." Onshape creates a blank assembly and opens it in the main workspace.

Now drag each part from the left panel into the assembly. Click on a part name in the tree, hold, and drag it into the assembly view. Onshape positions each part at the location it occupied in its original part studio. Repeat this for every part you want to export together. You can arrange them however you like by clicking and dragging in the workspace, but for export purposes the arrangement doesn't matter — only that they're all in the same assembly.

Exporting the assembly as a single file

Once all parts are in your assembly, right-click the assembly name in the left panel. A menu appears with several options. Click "Export" near the bottom. Onshape opens an export dialog where you choose your file format and name.

Select your format from the dropdown menu. STEP (.step or .stp) is the most widely compatible format and works with nearly every CAD program and manufacturing tool. STL (.stl) is best if you're sending the file to a 3D printer, because it converts the geometry to a mesh of triangles that slicing software understands. IGES (.iges) is older but still used in some industries. Parasolid (.x_t) works with Siemens NX and some other programs. Choose the format your next step requires, enter a filename, and click "Export." Onshape downloads the file to your computer.

What happens when parts export as one file

When you export an assembly, Onshape merges all the part geometry into a single solid body in the output file. This is different from exporting parts individually — you get one object, not separate components you can move independently. Open the exported file in your CAD software or viewer to confirm all parts are present and positioned correctly before you use it for manufacturing, 3D printing, or sharing with a team.

If you need to keep parts separate in the exported file so someone else can move them around, export each part individually instead. Right-click each part in your document tree, select "Export," and save them as separate files. Then the person receiving them can import all files into their own assembly.

Handling large assemblies and performance

Onshape can export assemblies with dozens of parts, but very large files (hundreds of parts or millions of polygons) may take longer to process. If your export seems stuck, wait a few minutes — Onshape is converting the geometry. If it fails, try exporting in STEP format first, as it's usually faster than STL for complex assemblies.

If your assembly contains parts with very high detail (thousands of sketches, complex surfacing), consider hiding or deleting unnecessary parts before export. This reduces file size and export time. You can always undo the deletion afterward since Onshape tracks your document history.

Exporting from an existing assembly

If your parts are already organized in an assembly, skip the creation step and go straight to export. Right-click the assembly name in the left panel and select "Export." Choose your format and filename, then download. This is the fastest path if your document is already set up as an assembly.

Check that the assembly contains all the parts you want to export. Click the assembly name to expand it in the left panel and see every part it holds. If parts are missing, drag them in from elsewhere in your document before exporting.

Frequently Asked Questions

Can I export parts without creating an assembly?

No. Onshape requires parts to be inside an assembly to merge them into a single file. You can export individual parts separately, but combining them into one file requires an assembly. Creating an assembly takes less than a minute.

Will the exported file show my parts as separate objects I can move?

No. When you export an assembly, all parts merge into one solid body. If you need to keep parts movable in the exported file, export each part individually and have the recipient import them into their own assembly.

What format should I use for 3D printing?

Use STL format. 3D printer software and slicing programs expect STL files. STL converts your geometry to a mesh of triangles, which is what printers need to build the object layer by layer.

Can I export an assembly that contains sub-assemblies?

Yes. Onshape flattens nested assemblies during export, so all parts from all sub-assemblies merge into the single output file. The hierarchy doesn't matter — you get one combined geometry.

What if my exported file is too large to email or upload?

Try exporting in STEP format instead of STL, as STEP files are usually smaller. You can also delete or hide parts you don't need before exporting. If the file is still large, split it into multiple assemblies and export them separately, then have the recipient import both files.