Use this STEP to 3MF converter when you have a CAD part and need a mesh file for a 3MF printing workflow. Open a .step or .stp file, choose how finely to mesh its curves, and preview the result before saving it. The conversion runs on your device, with no model upload or account required.

From a CAD part to a file for your slicer

You might have downloaded a STEP bracket or received a part from a designer, but need a .3mf file to share or import into your printing workflow. Converting turns the CAD surfaces into triangles and packages them with declared units.

You may not need this extra step if your slicer already opens STEP. PrusaSlicer supports STEP import, for example, and turns it into a mesh during import. Use this converter when you specifically need a separate 3MF file, and keep the original STEP for later CAD edits.

What carries over into the 3MF

The output represents the part's shape as a triangle mesh. Flat faces stay flat; curved surfaces are approximated by small triangles. Finer settings follow curves more closely but usually produce larger files.

  • Size and units: the converter reads the CAD geometry in millimeters and declares millimeters in the output. Check a known dimension in your slicer before printing.
  • Multiple parts: imported geometry is combined into one mesh object. Separate part names and the CAD assembly structure are not retained.
  • Colors and materials: these are not exported, even if the STEP file contains them.
  • CAD data: exact surfaces and assembly constraints are not stored in the mesh. The conversion does not create an editable feature tree.

A 3MF file can hold much more than a mesh, but this download is a model, not a saved slicer project. You still choose the printer, filament, layer height, supports, and placement in your slicer.

Choosing the mesh quality

  • Draft, 0.20 mm: useful for a quick check or a smaller file when curved detail matters less.
  • Balanced, 0.05 mm: a starting point for most printed parts.
  • Fine, 0.02 mm: useful for round surfaces that look faceted at coarser settings. Expect more triangles and a larger download.

These values control how closely the mesh follows the CAD surfaces. They are not layer heights or a guarantee of the finished print's accuracy. A part made only of flat faces may look the same at all three settings.

If the result needs another look

Curves look angular: try Fine and convert again. If the STEP itself contains faceted geometry, a finer setting cannot restore the original smooth surface.

A large assembly takes too long: try Draft, or export just the part you need from your CAD app. Conversion uses your device's memory and processing power; a complex assembly can take much longer than a simple part.

The file will not convert: check that it is a real, nonempty STEP export. Renaming another file's extension will not work. If the reader cannot find surfaces to mesh, re-export the solid or surface model from CAD. Clear the failed file before trying again.

STEP and 3MF serve different jobs

STEP is a neutral CAD exchange format used to move parts and assemblies between design programs. The .step and .stp extensions refer to the same format.

3MF is a package format for 3D manufacturing. The 3MF specification supports mesh geometry, units, and additional data such as materials. Which data you get depends on the exporter. This tool writes the mesh and its units; it does not generate printer instructions.

Check the model, then prepare the print

Open your download in a slicer, check its dimensions and orientation, then choose your print settings. Slice it and inspect the layers before sending the job to your printer.

For another look at the mesh, use the 3MF Viewer. If your workflow asks for STL, use the Free STEP to STL Converter directly. If your starting file is already an STL, use the Free STL to 3MF Converter.