stl2step turns an STL or 3MF mesh back into a solid: the triangles become exact planes, cylinders, cones and fillets, and their intersections become real edges. What comes out is a STEP file made of analytic surfaces — not a mesh wrapped in a solid, but geometry a CAD system can work with and build on: dimension it, change a fit, add a pocket, put the part on the machine.
Why go back at all? Because the mesh — an STL or a 3MF — is often everything that is left: a customer sends one, a supplier will not hand out the source, the part comes from a download portal, or the original CAD file was lost two computers ago. The usual way out is to rebuild the part by hand: measuring every diameter off the mesh and drawing it again. With practice that goes quickly — but it is manual work, it repeats for every part, and every dimension taken off the mesh is an estimate. stl2step measures those dimensions from the mesh, and it takes seconds.
Every file is checked back against its mesh, and the largest measured deviation is stated in the result, in millimetres. So the question whether the part is accurate enough for your work is settled before you download it — a number instead of a promise.
The tool does not load in this view without JavaScript. Open www.step2gcode.com/en/stl2step in your browser and drop your STL or 3MF file into the field.
| Surface type | Recognised as | Dimension in the report |
|---|---|---|
| Plane | surface without curvature | area in mm² |
| Cylinder | hole, boss, rounded wall | diameter |
| Cone | countersink, chamfer, drill point, tapered boss | full opening angle in degrees |
| Torus | fillet running along an edge | tube radius (the drawing dimension) |
| Freeform | not reconstructed yet | file is rejected, with a reason |
The uploaded file is processed for the reconstruction and not kept afterwards; the result stays on the server for at most 24 hours and is then deleted. Processing takes place in Germany. No registration, no installation.
If the source file still exists, it is always the better route — a reconstruction only recovers what is in the mesh, not the design intent. Often it is gone though: a customer file, a supplier part, a download portal, a lost computer. Redrawing by hand is then the fallback: doable, and quick with practice, but manual work for every part, and every dimension taken off the mesh is a possible mistake. stl2step measures those dimensions from the mesh and states the deviation.
If the part is made of geometric primitives: yes. stl2step recognises planes, cylinders, cones and fillets, intersects them into exact edges and writes a solid from that. Freeform surfaces and raw 3D scans are out of reach — such files are rejected rather than badly reconstructed.
The largest deviation between the built solid and your mesh is measured and stated in the result. For cleanly designed parts it is typically in the range of thousandths of a millimetre; above that the file is still delivered, but with the deviation named, so the decision stays yours.
A converter packages the triangles; every facet stays its own face. stl2step replaces them with the surface they describe — a hole becomes a cylinder with a diameter again, a chamfer a cone with an angle.
Yes. If the file contains several separate bodies, the mesh is split into its shells, each body is reconstructed individually, and the STEP file contains them as separate solids.
A STEP file carries no feature tree. If the part is an extrusion, its contour comes out alongside as DXF: sketch plus thickness, so the part can be rebuilt parametrically in CAD. It is an addition, not a replacement, and costs nothing extra.
Same as step2gcode: uploading, diagnosis and building are free, only the download is billed. There is a monthly free quota, after that one model costs one credit — no subscription. The STEP solid and the DXF contour belong to the same part and count once together.
To the G-code generator: STEP, DXF and SVG straight to G-code