Free online 3DM to IGES converter

A downstream CAD system, CNC workflow, or supplier portal may accept IGES but not Rhino’s native 3DM format. Exporting to IGES provides a neutral exchange file for curves, surfaces, and supported solid geometry.

What the 3DM format is

3DM is the native format of McNeel Rhinoceros (Rhino), based on the openNURBS library. It stores NURBS curves and surfaces, polysurfaces, meshes, annotations, layers, blocks, materials, and construction data. Rhino, Grasshopper workflows, and other applications that use openNURBS create or read 3DM files in industrial design, jewelry, architecture, product development, and engineering.

What the IGES format is

IGES is a neutral CAD exchange format usually saved as .igs or .iges. It can represent curves, trimmed NURBS surfaces, annotations, and some solid entities, although support for solid IGES entities varies between applications. Older CAD, CAM, inspection, and engineering systems commonly accept IGES when they cannot read 3DM.

IGES transfers geometric data rather than a complete Rhino document. Feature history, Grasshopper definitions, parametric constraints, assemblies, layers, materials, textures, and many object attributes may be lost. A receiving CAD system may import one Rhino polysurface as multiple trimmed surfaces instead of a recognized solid.

How to convert 3DM to IGES in Rhino

1. Open the .3dm file in Rhino.
2. Verify the document units in File → Properties → Units. Match the unit system required by the receiving CAD or manufacturing system; changing units can alter scale if Rhino’s unit-conversion options are not handled correctly.
3. Check the model before export. Use Analyze → Edge Tools → Show Edges to find naked edges, and run Rhino’s object and geometry diagnostics on objects that report errors. Repair gaps and invalid surfaces before conversion.
4. Select only the geometry required by the recipient. Use File → Export Selected to exclude construction geometry, reference meshes, or unwanted objects; use File → Export for the complete document.
5. Choose IGES (*.igs; *.iges), enter the output filename, and confirm the export.
6. In the IGES export options, retain trimmed NURBS surfaces unless the recipient specifies another entity type, IGES scheme, tolerance, or surface-splitting method. The best settings depend on the importing system.
7. Open the exported file in the target CAD application or a compatible viewer. Check units, scale, surface joins, naked edges, normals, and whether closed geometry was recognized as a solid.

Other conversion options

CAD Exchanger Cloud can perform browser-based CAD conversion when its current format list supports both 3DM input and IGES output. Upload the file, select IGES, download the result, and verify it in the destination CAD system. Online services may impose file-size or geometry limits, and confidential designs should not be uploaded without reviewing retention and privacy terms.

For offline batch conversion, a commercial translator such as Datakit CrossManager may be suitable if its installed version lists 3DM as an input format and IGES as an output format. Availability and supported entities vary by version, so test a representative model before processing a full dataset. Rhino remains the most predictable option when the source file contains Rhino-specific geometry or document data.

Quality and compatibility limitations

IGES generally preserves shape, not the editable Rhino structure. Meshes may be omitted or converted poorly, and render materials, textures, lights, construction planes, dimensions, object history, and Grasshopper logic may disappear. Use a surface- or solid-based Rhino model when the recipient needs editable CAD geometry.

A closed Rhino polysurface can become separate IGES surfaces, and an already open model will remain open after export. Use commands such as _ShowEdges, _Join, and _What to inspect and repair the source; conversion cannot create missing faces or close pre-existing gaps. If the recipient supports it, ask for STEP instead: STEP commonly provides more reliable solid topology and broader modern CAD exchange than IGES, while the recipient’s importer should determine the final format.