Convert IGS to STL

Why convert IGS to STL?

A file ending in .igs is an IGES file, using the short extension from systems that limited names to three characters. You will most often meet it in downloads from older supplier catalogues, legacy CAD archives and CAM exports. Slicers do not read it, so IGS to STL is the step that turns exact curves and surfaces into a triangle mesh you can print. MeshShift tessellates with OpenCascade in the browser and offers draft, normal and fine quality. Because IGS files frequently hold surfaces rather than a closed solid, check the result for gaps. The unit stored in the file sets the size, so a model in inches should still come out at its real dimensions in millimetres.

How to convert IGS to STL

1. Drop your IGS file onto the converter — it opens in your browser, nothing is uploaded.
2. Check the preview and the dimensions in mm; fix units or the up axis in “Units & orientation” if the size or orientation looks wrong.
3. Choose STL as the output (binary is smaller; ASCII is human-readable) and click Convert. Several files download as one ZIP.

What carries over from IGS to STL

What changes

• Surfaces are approximated by flat triangles at the selected quality.
• Open surface sets can produce a mesh that is not watertight.
• CAD layers, colours and entity names are dropped.
• Everything is merged into a single STL mesh.

Tips

• Compare the bounding box shown here with the original drawing to confirm units.
• Use the print check to see holes and non-manifold edges before slicing.
• If the converted mesh looks incomplete, the IGS may contain untrimmed surfaces; try a higher quality or re-export from CAD.

About IGS files

IGES was first published in 1980 by the US National Bureau of Standards, with participation from Boeing, General Electric and others, as one of the earliest standards for moving CAD data between different systems. Files use the .igs or .iges extension and are fixed-width 80-column text records divided into Start, Global, Directory Entry, Parameter Data and Terminate sections, a layout that reflects its punched-card heritage. IGES describes wireframe curves, trimmed and untrimmed NURBS surfaces, and, in later revisions, solids, but in practice it is mostly used for surface data. The format has not been updated since version 5.3 in 1996; STEP replaced it as the preferred standard. Even so, aerospace, automotive and tooling companies keep large IGES archives, and some CAM and surface-modelling programs still ask for it.

About STL files

STL was created by 3D Systems in the late 1980s for its stereolithography machines, and it became the default exchange format for 3D printing. A file describes a surface as a list of triangles, each with three vertices and a facet normal. That is all it contains. There is no header field for units, no colour, no texture and no notion of separate parts. Two flavours exist: ASCII, which is readable text but large, and binary, which spends exactly 50 bytes per triangle after an 80-byte header and a 4-byte triangle count. Binary is what almost every modern tool writes. Because the format is so small and so old, every slicer, CAD package and mesh editor can read it, which is why hobbyists still download most printable models as STL from sites like Printables and Thingiverse.

3D printing notes

STL is still the safest file to hand to a slicer. Bambu Studio, PrusaSlicer, OrcaSlicer, Cura and the resin tools Chitubox and Lychee all import it, and they all treat the numbers as millimetres. The usual problems are scale (a model exported from a metre-based tool arrives 1000 times too small) and meshes that are not watertight, which makes slicers fill or skip regions. MeshShift shows the real dimensions before you convert and can scale from metres automatically. Its print check lists holes, non-manifold edges and flipped normals, and one click rebuilds a closed solid at the same size. If you need colours or several plates in one file, use 3MF instead.

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