Convert 3DM to STL, free and in your browser

What the STL keeps

An STL is a list of triangles and nothing else: no materials, no colours, no part names and no unit. The converter writes every visible part into one binary STL in millimetres, the unit printers, casting houses and slicers assume, whatever unit the 3DM was drawn in (a file in inches or centimetres is scaled). Axes stay as they were in Rhino, with Z up, so the piece stands the same way on a build plate. Each triangle gets its facet normal from its corners.

An STL with many parts is still one mesh to the program that opens it. To keep parts apart, convert to GLB instead, which keeps the names.

Why does it say the 3DM has no meshes?

A 3DM keeps two things for each surface: the exact NURBS surface, and the render mesh Rhino draws it with in a shaded viewport. A browser cannot turn NURBS into triangles, so the converter takes the render meshes. If it says the file has no meshes, open the file in Rhino, set a viewport to Shaded or Rendered so every object gets a render mesh, and save without Save Small. For finer triangles, raise the render mesh quality (Document Properties → Mesh) before saving. MatrixGold and RhinoGold files are 3DM files and convert the same way.

What is left out

Curves, points, dimensions and other construction objects are not surfaces and are left out. Objects on hidden layers, and hidden objects, are left out too, so the file holds what you see in Rhino; the converter says how many it skipped. Blocks are expanded into their copies.

Is the STL good enough for casting?

The STL is exactly as fine as the render meshes in the file. Rhino's default render mesh is made for the screen, so for a casting or print file raise the mesh density first, or export the STL from Rhino with your caster's settings. Check that the parts are closed solids before sending: a render mesh of an open surface makes an open STL. Jart's cast check reads the same meshes and reports thin walls and stone seats.

Private by design

Nothing is uploaded. The page reads your file with the browser's file access, converts it on your own computer (the heavy part in a background worker, so the tab stays responsive) and hands the result straight back as a download. Our server sees only that this page was loaded.

Same importer as the studio

The converter uses the studio's own importer, so a file that converts here opens in Jart the same way. What each format keeps; to look at a file first, use the 3D viewer; the other converters: 3DM to GLB converter, STL to GLB converter.