Free online BREP to IGS converter

Source format: BREP

BREP stands for boundary representation, a CAD geometry format used to describe 3D solids and surfaces by their boundaries rather than by mesh triangles. It is commonly associated with CAD systems such as Open CASCADE-based applications and other engineering software that can store precise analytic geometry, edges, faces, and topological relationships. BREP files are typically used for product design, mechanical engineering, and manufacturing workflows where exact geometry matters.

Target format: IGS

IGS or IGES is a widely supported CAD exchange format used to share 2D and 3D geometry between different design systems. Its main advantage is broad compatibility across CAD platforms, making it useful for exchanging surfaces, wireframes, and some solid-model data. IGS is often used when a model must be opened in another CAD package, sent to a supplier, or archived in a neutral interchange format.

How to perform the conversion

The most reliable way to convert BREP to IGS is with a CAD application that can open BREP geometry and export IGES. A common choice is FreeCAD, which supports both formats through its CAD import/export tools.

1. Open FreeCAD.
2. Use File → Open and select your .brep file.
3. Verify that the model loads correctly and appears as a solid or surface body.
4. Choose File → Export.
5. Select IGES as the output type and save the file with a .igs or .iges extension.
6. If prompted, confirm export options such as units or shape tolerance.

Other desktop CAD tools that may support this workflow include Open CASCADE-based utilities, CAD Assistant, SolidWorks, CATIA, Siemens NX, or Autodesk Inventor, depending on the source file’s origin and the software’s import/export capabilities. The key requirement is that the program must be able to read the BREP geometry and write IGES output.

Notes on quality and limitations

BREP to IGS is a geometry translation, not a perfect format swap. Because IGES is an older exchange standard, some BREP-specific information may be lost during export, such as advanced topology, feature history, parametric constraints, or assembly metadata. In many cases, the resulting IGS file preserves the visible shape well, but downstream CAD systems may interpret surfaces, trims, or tolerances differently.

For best results, use the same units in both systems and inspect the exported model for gaps, flipped faces, or missing surfaces. If the BREP model contains complex solids, the IGES output may be more reliable for surface exchange than for fully editable solid modeling. When exact downstream editing is important, test the file in the target CAD application before relying on it for production use.