Stereolithography File Format (STL)

(or STL: Stupid Triangles and Lot’s of them)

The transformation from digital to physical has to do with the most common file format that 3D printers read from, which is defined as an “Stererolithography” file or STL for short.  This file format basically wraps a fine mesh around the object.

At an upclose level this mesh is nothing more than tiny triangles arranged perfectly to cover an object.  The best example of what these look like to a 3D printer is the bag that oranges come in at the grocery store.  Much the same way as these bags wraps the objects together, an STL file does the same for the CAD geometry.

STL files can be tricky to edit because if the mesh suffers a tear, the machine is unable to read the file and this causes the problems mentioned before.  This is usually due to the triangles not lining up perfectly and as a result fail to share a common edge or having a gap. Much like how oranges spill out from a torn bag, the contents of the model behave the same way.

STL use goes back to Computer Aided Manufacturing (CAM) machines and the ability of the file format to describe surface geometry in three dimensions without using color, texture, or other CAD model characteristics.