For beginners, exporting an STL 3D model involves opening your design in software (like Tinkercad, Blender), selecting the model, choosing "Export" or "Save As," and picking STL as the file format.
Check basic settings: Binary STL (smaller, better for 3D printing) is more common than ASCII (text-based, larger). Ensure your model is "watertight" (no holes/gaps)—STLs need closed surfaces for printing or machining.
For free tools: Tinkercad has a direct "Export" button in the top menu; Blender uses "File > Export > STL." If you get errors, simplify the model (reducing polygons) first to fix issues.