Convert AMF to STL

Why convert AMF to STL?

AMF, the Additive Manufacturing File Format, was designed as a successor to STL, with support for units, colours, materials and curved patches. It never gained wide adoption, and 3MF took over that role, but AMF files still appear in older slicer exports, some research projects and files from machines that used it, such as certain Stratasys and Slic3r workflows. Many current slicers no longer open it, which is the main reason to convert AMF to STL. The mesh is read, the units declared in the file are converted to millimetres, and everything is merged into one STL. Colours and material assignments are dropped, since STL cannot hold them. AMF files are often zipped XML, and both forms are read.

How to convert AMF to STL

1. Drop your AMF 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 AMF to STL

What changes

• Colours and material assignments are discarded.
• Multiple objects are merged into a single mesh.
• The unit declared in the AMF is converted to millimetres.
• Curved patches, where used, are read as their triangle mesh.

Tips

• If you want to keep colours, convert to 3MF instead.
• Check the size in the viewer; the AMF unit should give the right dimensions.
• Run the print check if the AMF came from an older export that may have flipped normals.

About AMF files

AMF was standardised as ASTM F2915 and later ISO/ASTM 52915, with the aim of fixing the shortcomings of STL for additive manufacturing. A file is XML, optionally compressed as a ZIP, and describes one or more objects made of a vertex list and volumes of triangles. Unlike STL, it declares units, such as millimetre, inch or micrometre, and can attach colours and materials to volumes or even to individual triangles, with gradients between them. The specification also allows curved triangles, constellations that arrange several objects, and custom metadata. In practice it was overtaken by 3MF, which came from industry backers and gained support in Windows and the main slicers. AMF files still appear from some multi-material printers and research tools, and from older exporters in Cura, Slic3r and Meshmixer.

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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