STL File Preparation Guide

The STL file format has become the Rapid Prototyping industry's defacto standard and is used by almost all rapid prototyping machines. This format approximates the surfaces of a solid model with triangles. For a simple model such as a sphere, the surfaces can be approximated with triangles and depending on the resolution chosen in the CAD system the sphere will be made up of more or less triangles as shown below.

Always set your STL resolution that is suitable to the model you are trying to make. If the model is largely flat surfaces then the resolution is not so important. If the model has many curves then a higher resolution is generally required.

Important things to know about STL files that are suitable for 3D printing

• Your model must be a 'fully enclosed solid'. This means that it cannot be an 'open surface model'. An open surface model is one made up of infinitely thin surfaces and that has an opening on it somewhere, which means that, as the surfaces are infinitely thin, there is nothing there to print.
• All the 'normals' on your STL file must face outward. A surface has 2 faces, one which is intended to be seen by the viewer, and the other which will be 'inside' the model. The 'normals' are the faces of a surface that are intended to be visible to the viewer, so all these should face outwards.
• As a general rule save each of your components as a separate STL file. If you save components with multiple bodies as a single STL file some 3D printing systems may not be able to handle them.