Overview STLS and OBJs are file types used for 3D models. GCode,, X3G and S3G are toolpath files containing instructions for 3D printers. STL An STL is a widely-used type of 3D model file. It consists of surfaces made up of triangles. Each triangle has an inner side and an outer side. The outer side is called the “normal.” In a well-formed STL, all the normals face outward and the surface is continuous, with no holes. When a model meets these standards, it is referred to as “manifold.” STLs with normals that face inwards (inverted normals) may be printable, but manifold models are typically considered mandatory for 3D printing. STLs are compatible with many different 3D modeling programs and have become the standard file type for 3D printable models. SolidWorks®, Rhinoceros®, and most Autodesk® programs will export STL files, and there are free plugins available that will allow you to export STLs from SketchUp®. OBJ An OBJ is another type of 3D model file. It is also used by...