STEP / STP to STL Converter Community

What this tool does

STEP (.step / .stp) and IGES (.iges / .igs) files are the neutral formats CAD programs use to exchange true solid models — but 3D printers and slicers only understand triangle meshes such as STL or 3MF. Converting between them means tessellating the exact curved surfaces of the solid into triangles. This converter does exactly that with OpenCascade, the same open-source CAD kernel used by FreeCAD, running as WebAssembly inside your browser tab.

How to use it, step by step

1. Export your model from Onshape / Fusion / SolidWorks as STEP and drop it in.
2. Choose STL (or 3MF) and a mesh quality — Normal suits most prints.
3. Check the 3D preview, size and volume.
4. Download the file and open it in your slicer.

Tips from the guide

• Most CAD packages can export STL directly — but exporting STEP and converting here lets you choose a finer or coarser mesh than the CAD default.
• Check the size in the stats: STEP files carry units, so the converter outputs millimetres by default (what slicers expect).
• For assemblies, all parts are merged into one mesh; export parts separately if you need to print them individually.
• If curves look faceted in the slicer, raise the quality one step and convert again.

Common mistakes to avoid

• Choosing Ultra quality for a simple part and getting a huge, slow-to-slice file.
• Expecting a surface-only IGES (no solid) to become a watertight printable mesh — surfaces need to be closed in CAD first.
• Forgetting that STL carries no unit: always confirm the size in the preview matches your intent.

Who uses it

• Students and hobbyists with Onshape/Fusion free accounts. Get from a STEP download to a printable STL without installing anything.
• Makers sharing models. Turn CAD downloads from manufacturers (STEP) into print-ready meshes.
• Engineers handling confidential parts. Convert locally so the geometry never touches a third-party server.

How to ask a question people can answer

A good thread on the STEP / STP to STL Converter saves everyone time. Start with a title that names the exact problem, such as the input you used, the result you expected and the result you got. A title like “Not working” is hard to answer, while a title with the specifics gets replies quickly.

• Say what you tried. List the steps you followed and any settings you changed, so replies do not repeat what you already did.
• Share a small example. A short sample input and the output you saw is worth more than a long description. Remove anything private first.
• Mention your setup. Your device, browser and whether you are on a phone or a computer can explain many odd results.
• One question per thread. Separate topics get clearer answers and are easier to find later with the search box above.
• Come back and reply. If a suggestion worked, say so and upvote it, and if you found the fix yourself, post it for the next person.

Community rules

Be kind, stay on topic and keep personal data out of your posts. Do not post adult, hateful or illegal content, advertising or repeated links. Every post is shown with its author’s username and date, and posts that break these rules can be hidden by moderators. This space is for help with the STEP / STP to STL Converter and related tasks, and it is separate from the sitewide discussion forum where broader topics live.