How to convert IGES to STEP without losing the solid
IGES stores surfaces; STEP stores solids. Converting is not a re-save but a repair job: the surfaces have to be stitched into a closed body first, which is why the conversion belongs in a CAD kernel rather than in a web uploader.
Why there is no uploader on this page
IGES is a closed format that no browser can read, so an in-page converter would have to send your file to a server. The procedure below does the job properly in the application that owns the format — and where a browser-side route exists, it is linked underneath.
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Paso a paso
- 1Open the .igs file in FreeCAD, SolidWorks, Inventor, Fusion 360 or Rhino — anything with a solid modelling kernel.
- 2Run the import diagnostic and heal the geometry: sew or knit the surfaces, then close any remaining gaps within the model tolerance.
- 3Confirm the result is a solid, not a surface body (check the volume or mass properties — a surface body reports none).
- 4Export STEP, choosing AP214 for assemblies and colours or AP203 for single parts with the widest compatibility.
- 5Re-open the STEP in a different package to verify before issuing it to the machine shop.
Aspectos a tener en cuenta
- If knitting fails, the original IGES was exported with too loose a tolerance. Ask for a fresh export at a tighter tolerance, or for STEP directly.
- IGES trimmed surfaces often arrive duplicated; delete the duplicates before sewing or the knit will never close.
- Colours, layer names and assembly structure rarely survive IGES, so expect to rebuild them.
- Analytic surfaces can become NURBS approximations, which slightly changes downstream fillets.
The older neutral CAD format. Exchanges surfaces and curves rather than watertight solids, so it is a fallback when STEP fails.
The ISO-standard solid-model exchange format for mechanical work — carries true solids and assembly structure between SolidWorks, Inventor, CATIA and NX.
Preguntas de delineantes
Why does my converted STEP still behave like a surface model?
The surfaces were never closed into a solid. Run the heal/sew tools and check mass properties before exporting.
Is there an online IGES to STEP converter?
Server-side services exist, but they upload your part geometry. FreeCAD performs the same conversion locally at no cost.
AP203 or AP214?
AP214 keeps assembly structure and colour; AP203 is the leaner choice for a single part where maximum compatibility matters.
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