Free online 3MF to FCSTD converter

What the 3MF format is

3MF is a ZIP-based 3D-printing format that can store one or more meshes, units, colors, materials, textures, and print-related metadata in a single file. Microsoft 3D Builder, Autodesk Meshmixer, PrusaSlicer, Bambu Studio, Cura, Blender, and many CAD applications can create or export .3mf files. You commonly encounter it when downloading a printable model or exporting a prepared model from a slicer.

What the FCSTD format is

FCStd is FreeCAD's native document format. It can store sketches, parametric features, assemblies, meshes, Part shapes, view settings, and the document's model tree. FCStd is appropriate when the result must be opened, measured, repaired, or further edited in FreeCAD. A mesh imported from 3MF remains a polygon model unless you convert it into a BRep shape or rebuild it with native FreeCAD features.

How to actually convert 3MF to FCSTD

Using FreeCAD

1. Open FreeCAD and create a new document.
2. Import the source with File → Import and select the .3mf file. In builds that support direct opening, File → Open also works.
3. Inspect the imported object in the Combo View. A 3MF containing several parts may appear as multiple mesh objects; keep them separate if they need independent editing.
4. Switch to the Part workbench, select a mesh, and choose Part → Create shape from mesh. Set a suitable sewing or tolerance value when FreeCAD prompts for one. Lower values preserve detail but can expose gaps; higher values may close small defects but alter the shape.
5. Select the resulting shape and use Part → Convert to solid if a solid is required. This step only succeeds when the mesh is closed and sufficiently valid.
6. Save the document with File → Save as and use an .FCStd filename.

For a file that only needs to be stored in FreeCAD, you can save the imported mesh directly as model.FCStd and omit the shape-to-solid conversion. FreeCAD's Mesh workbench provides repair tools for duplicate facets, holes, non-manifold edges, and other problems that prevent solid creation.

If you do not have desktop software installed, 101convert.com can convert the file online for free without installation. Open the resulting FCStd in FreeCAD and check its dimensions, object count, and geometry before using it for manufacturing.

Quality, compatibility, and limitations

• Mesh-to-solid conversion is not parametric conversion. The FCStd file will not contain the original sketches, constraints, feature history, or editable dimensions from a source CAD model.
• Curved surfaces in a 3MF are represented by triangles. Converting them to a solid creates many planar faces rather than true analytic cylinders, spheres, or fillets.
• A broken, open, self-intersecting, or non-manifold mesh may import successfully but fail during Part → Convert to solid. Repair it first or use the mesh as-is.
• Verify scale after import by measuring a known dimension. 3MF stores unit information, but incorrect exporter settings or importer behavior can still produce models at the wrong size.
• Print settings, slicer profiles, build plates, textures, and some material metadata generally do not become editable FreeCAD objects. Geometry and limited appearance information are the parts most likely to transfer.
• Very dense meshes can make FCStd files slow to open and edit. Decimate the source mesh only when reduced geometric accuracy is acceptable.