# STEP to 3MF Converter

> Turn CAD assemblies into a ready-to-slice 3MF: millimetres, every body as its own object if you like, and the CAD colors as filament colors.

Page: https://printpal.io/convert/step-to-3mf
Updated: 2026-11-12
Use it: open https://printpal.io/convert/step-to-3mf in a browser and drop a file. Free, no account, files are processed locally and never uploaded.

Slicers that import STEP mesh it themselves, but a 3MF fixes the tessellation, the units and the layout once, for anyone you send it to. The converter meshes every body with OpenCascade and writes a 3MF in millimetres, resting on the plate and centered on a 256 mm bed.

Tick **separate objects** to keep each body as its own 3MF object, so you can move or rotate parts independently. Part colors from AP214 and AP242 files become painted filaments (up to 16) that Bambu Studio and OrcaSlicer open with the colors assigned.

## How to convert STEP to 3MF

1. **Drop your STEP files.** Drop .step or .stp files. The STEP reader (about 7 MB) downloads the first time.
2. **Check the preview.** The model appears at the size and orientation it will have. Fix the file units, up axis or size under Size, units and orientation if needed.
3. **Choose 3MF options.** Keep parts as one object for a simple print, or tick separate objects to move them independently in the slicer.
4. **Convert and download.** One file downloads straight away. A batch gives a download per file and one .zip of all of them.

## What carries over

| | Result |
|---|---|
| Geometry | Exact STEP surfaces are tessellated into triangles with OpenCascade at the quality you pick (Draft, Normal or Fine). |
| Color | Colors become slicer filaments (up to 16), painted per triangle. |
| Units | Converted from the declared unit to millimetres, so it keeps its real size. |
| Orientation | Both are Z up, so it stays the right way up. |
| Objects | One object by default, or one 3MF object per part. Placed on Z = 0 and centered on a 256 mm plate. |
| Editability | Feature history and exact surfaces are not recoverable from a mesh. Keep the CAD file as your master. |

## STEP at a glance (ISO 10303-21 (Standard for the Exchange of Product model data))

STEP is the ISO standard for exchanging exact CAD geometry. Unlike a mesh it keeps true curves, so a 10 mm hole stays a perfect 10 mm cylinder until something turns it into triangles.

- **Stores:** Exact B-rep solids: planes, cylinders, fillets and splines as math, in assemblies
- **Color:** Per part and per face in AP214 and AP242; none in AP203
- **Units:** Declared in the file, usually millimetres
- **Up axis:** Whatever the CAD used; usually Z
- **Meshing:** Needs tessellation into triangles before printing or rendering
- **Opens in:** SolidWorks, Fusion, Onshape, FreeCAD, Inventor, CATIA, NX; Bambu Studio, OrcaSlicer, PrusaSlicer

## 3MF at a glance (3D Manufacturing Format)

The 3MF Consortium (founded 2015 by Microsoft, Autodesk, HP and others) designed 3MF to replace STL for printing. Bambu Studio, OrcaSlicer and PrusaSlicer save whole projects in it: plates, painted colors and print settings alongside the meshes.

- **Stores:** A zipped XML model: shared vertices, objects with transforms, a build plate
- **Color:** Materials and per-triangle colors; slicers add painted filament colors
- **Units:** Declared in the file, millimetres by default
- **Up axis:** Z
- **File size:** Compressed, usually under half of a binary STL
- **Opens in:** Bambu Studio, OrcaSlicer, PrusaSlicer, Cura, Creality Print

## Tips

- **Print orientation** The 3MF keeps the CAD orientation. Use the slicer's "Lay on face" to put a flat side down.
- **Many parts** Separate objects make arranging a multi-part print on several plates much easier.
- **Quality** Normal is right for most prints; pick Fine for small holes that must be round.

## FAQ

### Why not just import the STEP into my slicer?

You can, in Bambu Studio, OrcaSlicer and PrusaSlicer. A 3MF is useful when you send the job to someone else, use a slicer without STEP import, or want the colors and parts set up once.

### Are STEP colors kept?

Yes, as filament colors (up to 16), for files that store colors.

### What units is the 3MF in?

Millimetres, declared in the file, whatever unit the STEP was saved in.

### Is the converter free? Are there limits?

Free, with no sign-up, watermark or file count limit. Batches and files of a few hundred MB work on most laptops; the only limit is your device's memory.

### Are my files uploaded?

No. Files are read and written by JavaScript and WebAssembly in your browser and never sent to PrintPal. The STEP and IGES reader is the only extra download, once, from a public CDN.

## Related

- [3MF to STL Converter](https://printpal.io/convert/3mf-to-stl)
- [STEP to STL Converter](https://printpal.io/convert/step-to-stl)
- [STEP to OBJ Converter](https://printpal.io/convert/step-to-obj)
- [3MF to OBJ Converter](https://printpal.io/convert/3mf-to-obj)
- [STL to 3MF Converter](https://printpal.io/convert/stl-to-3mf)
- [OBJ to 3MF Converter](https://printpal.io/convert/obj-to-3mf)
- [GLB to 3MF Converter](https://printpal.io/convert/glb-to-3mf)
- [STEP File Viewer](https://printpal.io/tools/step-viewer)
- [3D model viewer](https://printpal.io/tools/3d-model-viewer)
- [3D model converter](https://printpal.io/tools/3d-model-converter)
- [Mesh Repair](https://printpal.io/tools/mesh-repair)
- PrintPal for LLMs: https://printpal.io/llms.txt