Convert 3MF to STL
Extract core 3MF mesh geometry, apply build transforms and download a binary STL in millimetre coordinates.
Supported input and output
ZIP32 packages with stored/deflated entries, a root model relationship, core mesh objects, declared units and multiple transformed build items.
From a build package to triangle geometry
A 3MF build item can place the same mesh more than once. This converter applies those placements and the declared unit scale before writing STL triangles. The downloaded STL contains those shells together, but carries neither the original build structure nor slicer settings. Choose millimetres when opening it in a slicer.
How to use this tool
- Choose a core mesh 3MF package.
- Review its source unit, transformed preview and conversion warnings.
- Convert and download the STL. Select millimetres when importing it elsewhere.
Limitations to check
- Component assemblies, cross-part models, required/recommended extensions, ZIP64 and encrypted archives are rejected. Only the documented core mesh subset is supported.
- Materials, colors, textures, metadata and slicer settings are discarded. Multiple build items are merged in build order as triangle shells, not boolean-unioned.
- Model units are normalized to mm, including build translations. Missing units use the 3MF-defined millimetre default and produce a warning. STL itself has no standard unit field.
- Binary STL uses 32-bit coordinates. Archive expansion, XML structure and mesh-size limits are enforced; malformed or degenerate geometry is rejected.
File and processing limits
- 3MF input up to 25 MiB; 128 ZIP entries, 32 MiB per expanded entry, 64 MiB total declared expansion and maximum ratio 200:1.
- XML: 16 MiB per part, 32 nesting levels and 1.5 million elements. Mesh: 750,000 vertices, 250,000 triangles, 256 build objects.
- Generated mesh output is limited to 64 MiB.
- 30 seconds per mesh job. Browser memory and device speed can impose lower practical limits.
Processing happens in this browser; your file and filename are not uploaded. Cancel, reset or replace the file to stop its worker. Downloads are generated locally.
Questions about this workflow
Why is my slicer-created 3MF rejected?
Some slicers use component assemblies, extensions or cross-part models outside the supported core mesh subset. Export a plain mesh-only 3MF or an STL from the source application. Renaming the package does not change its structure.