Free online BREP to 3MF converter

Source format: BREP

BREP stands for boundary representation, a common way to store 3D solid geometry in CAD systems. Instead of describing an object as a mesh of triangles, BREP defines the shape using its faces, edges, vertices, and surfaces. It is widely used in engineering, product design, and manufacturing workflows where precise geometry matters.

BREP data is typically found in CAD files such as STEP, IGES, or native CAD formats that preserve exact curves and surfaces. It is especially useful for parametric modeling, downstream machining, simulation, and design exchange between CAD applications.

Target format: 3MF

3MF is the 3D Manufacturing Format, an XML-based file format designed for 3D printing. It stores a model as a mesh along with useful manufacturing data such as units, materials, colors, textures, and build settings. Compared with older formats like STL, 3MF can preserve more information in a smaller, more modern package.

The main advantages of 3MF are better support for printing workflows, unit consistency, and the ability to carry richer model metadata. It is commonly used by 3D printing software, slicers, and additive manufacturing pipelines.

How to perform the conversion

Converting BREP to 3MF usually requires two steps: tessellating the exact CAD geometry into a polygon mesh, then exporting that mesh as 3MF. The best tool depends on where the BREP data comes from.

Option 1: Use CAD software that can open BREP-based models and export 3MF

1. Open the source model in a CAD application that supports BREP geometry, such as FreeCAD, Fusion 360, SolidWorks, or Rhino.
2. If the model is not already a mesh, convert or export it as a mesh with appropriate tessellation settings.
3. Choose File → Export or File → Save As.
4. Select 3MF as the output format.
5. Adjust export options if available, especially units, mesh quality, and whether to include colors or materials.
6. Save the file as model.3mf.

Option 2: Use FreeCAD for BREP-based geometry

1. Open the BREP-containing model in FreeCAD.
2. Switch to the appropriate workbench if needed and ensure the solid is valid.
3. Export the object using File → Export.
4. Pick 3MF Mesh or a similar 3MF export option if available in your version.
5. Confirm the mesh resolution is suitable for printing.
6. Save the result as output.3mf.

Option 3: Convert through an intermediate mesh format

If your CAD tool cannot export 3MF directly, export the BREP model to a mesh format such as OBJ or STL, then open that mesh in a slicer or 3D modeling tool that can export 3MF. This is often the most practical route when working with older CAD software.

Notes on quality, compatibility, or limitations

BREP to 3MF is not a one-to-one conversion. BREP stores exact analytic geometry, while 3MF stores a mesh approximation. That means curved surfaces are converted into polygons, and the final quality depends on the tessellation settings. Higher-quality meshes produce smoother prints but larger files.

Because 3MF is intended for manufacturing, it is important to check units after conversion. A model that is correct in millimeters can appear far too large or too small if the export settings are wrong. Also, not every BREP feature survives the conversion: parametric history, constraints, and exact surface definitions are usually lost.

For best results, verify that the exported 3MF is watertight, has correct normals, and opens properly in your slicer before printing. If the source model contains complex surfaces or tiny details, you may need to increase mesh resolution to avoid visible faceting.