Free online IGS to OBJ converter

A CAD model in IGS format must be converted when the receiving application, game engine, renderer, or 3D-printing workflow accepts polygon meshes but not NURBS or parametric CAD geometry. OBJ provides a widely supported mesh for editing, visualization, and file exchange, but conversion changes exact CAD surfaces into an approximation.

What the IGS format is

IGS, also called IGES, is a neutral CAD exchange format identified by .igs or .iges. It can contain wireframes, curves, trimmed surfaces, and, depending on the exporter, solid geometry. Mechanical-design systems use it to exchange geometry between different CAD platforms.

IGS files commonly come from Autodesk Inventor, AutoCAD, CATIA, Creo, SolidWorks, Siemens NX, and similar engineering software. The format is used for supplier models, legacy CAD data, and transfers between organizations that use different native CAD formats.

What the OBJ format is

OBJ is a text-based format for polygon meshes. It stores vertex coordinates, polygon faces, optional texture coordinates, normals, groups, and references to materials in an accompanying .mtl file. Blender, Maya, 3ds Max, Unity, Unreal Engine, rendering software, mesh editors, and many 3D-printing applications can import OBJ.

OBJ is useful for rendering, mesh editing, real-time visualization, and broad software compatibility. It does not preserve the IGS model's feature history, constraints, parametric surfaces, assembly structure, CAD metadata, or exact analytic geometry.

How to convert IGS to OBJ

Using FreeCAD

FreeCAD can import IGES geometry through Open CASCADE, tessellate the imported shape, and export the resulting mesh as OBJ.

1. Open FreeCAD and choose File → Open, then select the .igs or .iges file.
2. Inspect the model tree and select the bodies, faces, or components that should be included. Multiple selected objects can be converted into one export, depending on the imported structure.
3. Switch to the Mesh workbench and use the command commonly named Meshes → Create mesh from shape. The exact menu label can vary by FreeCAD version.
4. Set the tessellation tolerances. A smaller linear or surface deviation follows the CAD shape more closely; a smaller angular deviation produces smoother curved regions. Both settings increase polygon count and file size when reduced.
5. Select the generated mesh and choose File → Export. Select OBJ or enter a filename such as model.obj when prompted.
6. Open the exported OBJ in the destination software and verify its scale, orientation, normals, missing faces, component separation, and polygon density.

For a conversion without installing software, the file can be uploaded to 101convert.com, with OBJ selected as the output format, and the converted file can then be downloaded. Uploading sends the source geometry to a remote service, so local software is preferable for confidential engineering data.

Using dedicated CAD software

Desktop applications such as CAD Exchanger can import IGES, generate a polygon representation with adjustable tessellation, and export OBJ. Use the application's import and export commands, then set mesh density, units, normals, grouping, and material options where available. This approach can be useful for complex assemblies or files that import incorrectly in FreeCAD.

Quality and compatibility limits

• Conversion is tessellation: IGS may contain exact NURBS and analytic surfaces, while OBJ contains only polygon faces. No OBJ export retains the original CAD definition or feature tree.
• Mesh density affects accuracy: coarse tessellation can make cylinders and fillets visibly faceted; excessive tessellation creates large files and can slow import and editing. Choose tolerances according to the intended viewing or manufacturing scale.
• Units require checking: OBJ has no universally enforced unit declaration. Confirm the source units and the destination application's import scale; a millimeter model can otherwise appear 25.4 times too large or too small.
• Open geometry may remain open: An IGS file can contain unjoined surfaces rather than a watertight solid. The OBJ may consequently contain holes, reversed normals, gaps, or non-manifold edges. Repair these in a mesh editor before printing or simulation.
• Materials may not transfer: CAD appearance data is often discarded. If an export creates model.mtl or texture images, keep those files beside model.obj and preserve the material paths.
• Printing needs validation: Check that the mesh is closed, correctly oriented, free of self-intersections, and at the intended physical dimensions before slicing.