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.
The service fits 2.5D parts best — parts that were once designed in CAD and today only circulate as a mesh. That is the normal case on the 3D printing sites such as Printables, Thingiverse or MakerWorld: brackets, adapters, lids, mounts and fixtures were built in Fusion 360, Onshape or FreeCAD, but only the STL or 3MF for the slicer was published, and the STEP file sits with the author, if it still exists at all. Such parts are made of exactly the shapes stl2step recovers: flat faces, holes at right angles, chamfers, fillets running along the edges. A printable model becomes a solid again — one you can dimension, adapt and machine, turning a part made of PLA into one made of aluminium.
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 | faceted solid instead of exact surfaces (beta) |
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.
Yes — different names for the same thing. "Mesh to solid" is what CAD systems call it (Fusion 360 says "Mesh to BRep", SolidWorks "Convert mesh to solid"); "STL to STEP", "3MF to STEP" and "mesh to STEP" describe the same route through the file formats: a triangle mesh becomes a solid again, with surfaces you can measure and build on.
That is the case the service fits best. Most of those parts were designed in CAD and only published as STL or 3MF — they consist of flat faces, holes, chamfers and fillets, which is exactly what stl2step turns back into exact surfaces. That makes a printable model editable in CAD again: check the dimensions, adapt a hole to your own thread, machine the part from aluminium instead of printing it in PLA. Two things to note: the model keeps its author's licence — what you may do with it is stated there, not here. And purely organic or scanned models (figures, busts, reliefs) have no such faces; those get the faceted solid.
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 have no such faces. Those meshes are not turned away either: they get a faceted solid (beta) — a STEP file every CAD opens, useful as a reference body, for boolean operations and for remodelling, but without exact diameters. Whatever deviates from your mesh is measured and stated.
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. Your first model is free, 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