This is a post by Jason Piehl on the EAC Site.
The increased use of 3D printing, from hobbyists to professionals, has revolutionized the way ideas and products are brought to life. Multiple websites (GrabCAD, Thingiverse, etc.) provide over a million free downloadable files that can be printed on a variety of 3D printers. Everything from miniature drone blades to sci-fi figures to replacement parts for your vacuum cleaner are readily available. The possibilities for whatever application you have are almost unlimited. Almost.
The key to giving your 3D designs unlimited potential for customization is CAD modeling software. While there are many accessible 3D printing files created by others, the most satisfying way to bring your ideas to reality are files created by you! Files for 3D printing can be created from scratch or existing files can by modified to suit your application. Without the ability to create unique parts, a 3D printer can quickly become a novelty. As soon as the excitement of first initial prints wear off, the use and return on investment reduces as well.