The main advantage of additive fabrication is its ability to create any shape or feature, in super fine detail. Additive fabrication uses only the material that is needed to produce the part, CNC machine fabrication often causes a lot of waste as the part is formed from a block of material which can be expensive, with 3D printing however, you only pay for the material your actual model requires. What is an .STL File
CAD to STL
STL is short for stereo lithography invented by a company called 3D systems around about 1988. STL is also referred to as Standard Tessellation Language. STL is the standard data interface between CAD software and 3D printers.
An STL file approximates the shape of a part or assembly using triangular facets; it only carries information of the geometry that makes up a three dimensional surface and does not contain any textural or colour information associated with many CAD packages. Smaller facets produce a higher quality surface. Take a look at the image; this is a regular box shape, drawn using a standard CAD package and then saved as a .STL file. Notice on the flat surface of the box there are much larger triangles than on the filleted corners, the reason for this is that to make those surfaces less information is required, because they are flat, on the rounded corners however, a lot more shape is present, so in order to maintain these shapes more densely packed triangles are used. Save your part for a 3D printer many CAD packages will give the option to save, with more detail or less detail, this means smaller triangles, or bigger triangles (less detail).
Also a choice of binary or ASCII, Many users would choose Binary as the files tend to be more compact.