STL is the standard file type used by most or all rapid prototyping systems. A STL is a triangulated representation of a 3D CAD model (figure 1). The triangulation of a surface will cause faceting of the 3D model. The parameters used for outputting a STL will affect how much faceting occurs (figure 2 and 3). You cannot build the model any better or smoother than the STL file, so if the STL is coarse and faceted, that is what you can expect in the final model. In the CAD package, when exporting to STL, you may see parameters for chord height, deviation, angle tolerance, or something similar. These are the parameters that affect the faceting of the STL.You don’t necessarily want to go too small. The finer the STL the larger the file is in size, which will affect processing time in Insight as well as build time. Below is some information found on the Internet regarding exporting to STL from various CAD packages.