3MF to STL

preslice writes STL from the meshes it has already read, so the export happens in the tab and your .3mf is left alone.

How do I save one mesh as STL?

1. Drop the .3mf on preslice.co.
2. Open the 3MF Content tab and expand Mesh objects.
3. Click Export STL on the mesh you want.

The button sits on each mesh, not on each object, so an object built from three parts lists three meshes. The file takes the mesh's name, and an unnamed mesh saves as mesh-<id>.stl, such as mesh-3.stl.

How do I save every mesh at once?

Export all as STL sits in the Mesh objects header. It writes one ZIP named after your file, so benchy-plate.3mf gives you benchy-plate-stl.zip with one STL per mesh inside. Two meshes called Body become Body.stl and Body-2.stl.

Where does each part end up?

Where it was modelled, not where the slicer put it. The STL keeps each mesh's own coordinates, so a part you moved, rotated or scaled in the slicer comes out at its original place and size. Parts of one object that were placed against each other may no longer line up. Arrange them again in the slicer.

What does STL throw away?

Everything except the triangles. Colour and paint are gone, and there is no export per colour, here or in any slicer. Plates, filaments and every print setting stay behind. See 3MF against STL.

Is it ASCII or binary STL?

Binary. It is the smaller of the two forms and every slicer reads it. An STL keeps no units, so the millimetres the 3MF Core Specification records on the model are gone from the copy.

Where is Export STL in my slicer?

Bambu Studio and OrcaSlicer also offer Export as one STL when you right-click an object. Unlike preslice, the slicers write each part where it sits on the plate.

Can I get the STL from MakerWorld instead?

Often. A model page lists the files the designer uploaded, and many include STLs next to the .3mf. Some upload only a .3mf with print profiles, and then this page is the way out.

Can preslice write STEP or SVG?

No. See 3MF to STEP for Fusion and FreeCAD. For OBJ, see 3MF to OBJ.

Why keep the .3mf then?

Because the STL is a copy with the thinking removed. The .3mf still holds the plate, the filament choice and the settings, and you can send it to another slicer later.