STEP to STL Converter

Slicers for 3D printers want STL or 3MF, but designers and part suppliers send STEP. Converting usually means opening the model in a CAD program, or uploading it to a converter site and waiting. This page does it in your browser: the STEP file is read with Open CASCADE, tessellated into triangles, and the visible parts are written straight into an STL file on your computer.

Each STEP face is meshed with a tolerance relative to the model size, so small features stay smooth while big flat faces stay light. The STL is in millimetres, the unit slicers assume, whatever units the STEP file used. Parts are placed where the assembly puts them, so a multi-part file prints as laid out; untick parts to print one at a time.

Check the volume line before printing. If it says the model is not a closed solid, the file holds open surfaces (common with IGES) and the STL will not be watertight; ask for a solid STEP instead.

Why not just ask the designer for an STL? Often you can, but STL files are fixed at one resolution and lose the part names, while a STEP file lets you choose what to print and keeps a clean source. Makers download STEP parts from vendor catalogues for brackets, motor mounts and enclosures all the time, and this page turns them into something a slicer accepts in a few seconds, without installing FreeCAD or uploading a client design to an unknown converter site.

Large assemblies are fine. The model is read in a background worker, so the page stays responsive, and the 3D engine is cached after the first visit, so the next conversion starts at once. On a laptop a typical part converts in about a second; an assembly with hundreds of parts can take longer, with a progress message while it is read.

A few tips for clean prints. Turn the model to the Front and Top views to see which face should sit on the bed, since the STL keeps the orientation from the STEP file and most slicers let you lay a face flat afterwards. Use the size line to check the part fits your printer before you slice, and if the numbers look 25 times too small, the file was probably drawn in inches and saved without units. For a rough draft print the default mesh is plenty; curved faces such as bearing bores and fillets are split finely enough that facets do not show at normal layer heights.

The conversion happens on your device. The STEP file is not uploaded and the STL is handed to your browser as a download.

STL keeps only triangles: no colours, part names or exact curved geometry. Keep the STEP for machining and CAD work.