STL is still the standard format for 3D printing. It describes your model's surface as a mesh of triangles — and how you export it determines how well the print turns out. Here's how to get a clean, print-ready file out of the most common programs.
Exporting from your CAD program
The basics are the same regardless of program, but the menus differ:
- Fusion 360: Right-click the body or component and choose Save As Mesh (or Export → STL). Set Refinement to High for detailed parts.
- SolidWorks: File → Save As → choose STL, then open Options to adjust the resolution (Fine or Custom).
- Blender: File → Export → STL. First apply all modifiers and check the scale, since Blender doesn't work in millimetres by default.
- Tinkercad: Export → .STL. Tinkercad already works in millimetres, so it's the simplest option for beginners.
Resolution and tolerance
STL approximates curved surfaces with flat triangles. Too coarse a resolution gives angular cylinders and faceted curves; too fine gives needlessly large files.
Aim for a chord/deviation tolerance of around 0.01–0.05 mm for most parts. Flat boxes handle coarser settings, while gears and threads benefit from finer ones. If you don't need micrometre precision, a file of several hundred MB is unnecessary and only slows everything down.
Units and scale
The most common mistake we see is the wrong unit. The STL format stores no units at all — just numbers. Our process interprets them as millimetres, so model and export in mm.
If you get back a part in inches instead of cm, or 1000 times too large, it's almost always a unit clash. Check the dimensions in your program before exporting, and verify that a known dimension (e.g. a 20 mm hole) is correct.
Watertight meshes
A print-ready model must be watertight — a closed shell with no holes, gaps or flipped normals. Thin walls and loose surfaces that don't connect cause problems in the slicer.
- Use your program's tools to check and repair the mesh (Fusion: Mesh → Repair; Blender: 3D-Print Toolbox).
- Avoid walls thinner than roughly 0.8–1 mm, or they risk disappearing entirely.
- Make sure separate bodies that should join actually overlap.
Alternatives to STL: STEP and 3MF
STL discards all information beyond the geometry. Two modern alternatives are often better:
- STEP: Keeps exact mathematical surfaces instead of triangles — perfect if we might need to adjust or review the part.
- 3MF: A more compact format that can carry colour, units and multiple bodies in one file.
We accept all three. If you're unsure which suits your model, just send what you have — and we'll get in touch if anything needs adjusting. Upload your file for an instant quote, or read on about tolerances and fits before you submit.