Free online BREP to FCSTD converter

Source format: BREP

BREP stands for boundary representation, a CAD geometry format used to describe solid and surface models by their faces, edges, and vertices. It is commonly associated with Open CASCADE and other CAD kernels, and is often used in engineering workflows to exchange precise 3D geometry between modeling tools. A BREP file usually stores the shape definition itself, not drawings, assemblies, constraints, or parametric history.

Target format: FCSTD

FCSTD is the native document format of FreeCAD. It can store a full FreeCAD project, including imported geometry, parametric features, sketches, assemblies, document structure, and metadata. The main advantage of FCSTD is that it preserves the editable FreeCAD model state, making it suitable for continuing design work rather than just viewing geometry.

How to perform the conversion

The most practical way to convert BREP to FCSTD is to use FreeCAD, because FCSTD is FreeCAD’s own project format. The conversion is usually done by importing or opening the BREP geometry in FreeCAD and then saving the document as an FCSTD file.

1. Install and open FreeCAD.
2. Create a new document with File → New.
3. Import the BREP geometry with File → Import and select your .brep file. In some FreeCAD versions, you can also use File → Open if the file is recognized directly.
4. Check that the solid or surface appears correctly in the 3D view.
5. If needed, place the imported shape into a Part or Body workflow so it becomes part of your FreeCAD project structure.
6. Save the project as an FCSTD file using File → Save As and choose a filename such as model.fcstd.

If you prefer command-line automation, FreeCAD can also be scripted with Python, but for most users the GUI workflow is the simplest and most reliable approach for this conversion.

Notes on quality, compatibility, or limitations

BREP to FCSTD is not a true format translation in the sense of rebuilding parametric history. The BREP geometry is imported as shape data, and the resulting FCSTD file mainly acts as a FreeCAD container for that geometry. This means:

• Geometry is preserved, but original design features, sketches, and constraints from the source CAD system are usually lost.
• FCSTD files are project files, so they are best for continuing work in FreeCAD, not for exchanging geometry with non-FreeCAD tools.
• Compatibility depends on the BREP source; some BREP variants or complex solids may import with healing issues, missing faces, or tolerance problems.
• File size may increase because FCSTD stores the imported shape plus FreeCAD document data.

For best results, verify the imported model in FreeCAD before saving, especially if the BREP file comes from another CAD system or contains advanced surface geometry.