Free online STEP to IGS converter

A legacy CAD, CNC, metrology, or inspection program may accept IGS but not STEP, requiring the model to be exported before use. The conversion also provides a surface-based file for exchanging geometry with older systems, although it can discard design history and assembly information.

What the STEP format is

STEP is the common name for ISO 10303, a neutral CAD exchange standard used for 3D solids, surfaces, assemblies, product structure, colors, and selected metadata. Common application protocols include AP203 for configuration-controlled mechanical designs, AP214 for automotive and general mechanical data, and AP242 for newer model-based engineering workflows.

STEP files usually use .step or .stp. They are exported by CAD systems such as SolidWorks, Autodesk Inventor, Fusion, CATIA, Siemens NX, Creo, and FreeCAD. Engineers use them to exchange supplier models, transfer assemblies between CAD platforms, and import designs into CAM, simulation, rendering, and inspection software. Most conventional STEP files are text-based Part 21 files, but the STEP standard also defines other implementation methods.

What the IGS format is

IGS, also called IGES, means Initial Graphics Exchange Specification. Its usual extensions are .igs and .iges. IGES represents geometry through entities such as points, wireframe curves, surfaces, trimmed surfaces, annotations, and, in some implementations, solid-related topology.

IGES remains useful when a legacy CAD, CNC, metrology, or surface-modeling application does not support STEP. It commonly transfers individual curves, surfaces, tooling geometry, and older mechanical models. Compared with STEP, it generally carries assembly structure, product metadata, and solid-topology information less reliably. It is therefore primarily a compatibility format rather than the preferred modern format for exchanging complete parametric designs.

How to convert STEP to IGS

Using FreeCAD: FreeCAD can import STEP and export IGES without the original authoring application.

1. Install and open FreeCAD.
2. Choose File → Open, select the .step or .stp file, and wait for the model tree and 3D view to load.
3. Check the imported bodies, parts, and assembly components. Hide or remove objects that should not be included in the output.
4. Select every object that must be exported in the model tree. Use multi-selection when the import contains separate bodies or components.
5. Choose File → Export.
6. Enter a filename ending in .igs or .iges, select IGES in the file-type control if FreeCAD displays one, and save the file.
7. Open the exported file in the destination application. Check the complete model, units, face continuity, edges, and component placement.

STEP imports can appear as separate solids, shells, compounds, or assembly components. Selecting only one tree item can export only part of the source model. FreeCAD and other CAD programs may also offer an IGES export command under File → Export or a similar menu; the exact labels depend on the application and version.

Using 101convert.com: You can convert the file for free on 101convert.com without installing software. Upload the STEP file, choose IGS as the output format, start the conversion, and download the generated .igs file. Do not upload confidential or export-controlled engineering data unless the service's handling and retention terms meet your requirements; use a local CAD application for sensitive models.

Quality and compatibility limits

The conversion transfers geometry, not the original parametric model. Sketches, constraints, feature trees, construction history, formulas, and native CAD editing operations are normally lost. A STEP assembly may become separate IGES entities, and assembly hierarchy, part names, colors, layers, and metadata depend on the exporter and receiving software.

An IGES export may represent a solid as multiple trimmed surfaces rather than as a single usable solid. The destination program may need to sew or stitch those surfaces before applying solid operations. Tolerance differences, small gaps, missing trims, reversed surface normals, and invalid edge relationships can prevent sewing or cause downstream machining and inspection errors.

Check units after conversion. STEP commonly stores units explicitly, while an IGES importer may rely on a unit flag or a setting in its import dialog. Measure a known hole diameter, overall length, or other reference feature before manufacturing. Reopen the saved IGS file in the target application and run its geometry-check or repair function; a successful export does not prove that the receiving system can use every entity correctly.