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Export a solid
The STEP button under the Timeline stats, beside STL and OBJ, once a solid exists.
It writes model.step in millimetres. This is the export that carries the model itself rather than a picture of it: the faces, the edges and the surfaces they lie on, so what arrives at the other end is a part somebody can keep working on.
STEP against the mesh formats
| STEP | STL and OBJ | |
|---|---|---|
| Carries | Faces and surfaces | Triangles |
| A hole | A curved surface, exactly round | A many-sided prism |
| Read by | CAD, CAM, quoting and inspection | Slicers, renderers, mesh tools |
| Editable elsewhere | Yes | No |
A slicer wants STL. A shop, a machinist, or anyone opening your part in another CAD wants STEP. See export a mesh for the other two.
What goes in the file
Every visible body. Hiding a body with its eye leaves it out, which is how one part of a multi-body document is exported on its own.
The bodies go in together, so a document with three bodies gives one file holding three solids. They arrive positioned the way they stand here, joints and all.
The part is named. One body goes out under that body's name; several go out as Assembly.
Curves stay curves
A hole drawn as a circle is a round surface in the file, not the faceted approximation you see on screen. The triangles in the model view are how the solid is drawn; STEP carries what it is.
This is the practical difference between the two kinds of export. Measure a bore off an exported STL and you measure the polygon; measure it off the STEP and you measure the hole.
What you cannot export
No IGES, DXF, SVG or 3MF. Sketch geometry cannot be exported on its own, only the solid.
A body that came in as an imported mesh and never converted to real geometry cannot be written: there is nothing but triangles behind it. If any are in the document, the export says which were left out and writes the rest.
To keep an editable document, with its sketches, constraints and feature history, use Save. STEP carries the finished shape, not the recipe that built it.