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.

  • Files stay on your device
  • Free, no sign-up
  • Units and up axis handled
  • Batch and .zip

Drop a STEP file to convert

One file, many, or a .zip

In: STL · STEP · IGES · OBJ · 3MF · GLB · glTF · PLY · FBX · DAE · 3DS · AMF · VRML · ZIP

Converted on your device. Nothing is uploaded.

    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 from STEP to 3MF

    Worked out from what each format can store and what this converter writes. Nothing is changed silently: the preview shows the size and orientation before you download.

    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 to 3MF: what actually happens

    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.

    STEP at a glance

    ISO 10303-21 (Standard for the Exchange of Product model data) · .step, .stp

    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

    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.

    Open STEP files in the viewer

    3MF at a glance

    3D Manufacturing Format · .3mf

    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

    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.

    Open 3MF files in the viewer

    Tips for STEP to 3MF

    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.

    STEP to 3MF 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.