For many of the smaller details of my concept vehicle such as headlights and logos, these were much easier to be 3D printed rather than CNC machined out due to the accuracy needed in the shapes and the freedom with design you had. The two machines that I had access too were a Z- Corp and a Objet Printer.
The Z-Corp was a white powder printer which was able to print objects down to 2mm with quite alot of accuracy. The common working process with these parts was to collect the prints and then coat them in an Epoxy Resin which after drying allowed them to harden into a material that was much easier to sand and consequently paint with better strength. These prints were generally cheaper than the Objet Prints however the smaller you went, the weaker the prints were, my taillights originally being printed in Z Corp, had the consistency of a baked cookie, crumbling and bending at some points being generally far to fragile to work with. Noting the weakness of the smaller parts, the 3 larger prints that I needed to create were completed on the Z- Corp Machine maintaining a wall thickness of minimum 3mm all around to ensure rigidity in the printed structure.
The Objet Printer was an additive manufacture printer which printed in a polymer like material that was alot stronger than the equivalent Z-corp of the same size. Being costlier due to the support material that surrounded each part that was created, strategically placing parts flat on the bed was crucial to saving money. The parts that came out of the Objet were a translucent yellow polymer/plastic that took a while to clean but felt much stronger and flexible to work with than the Z-Corp Prints. I ended up using the Objet Printer for all my smaller parts as whilst the cost was slightly higher, the strength of the parts paid off due to the easy of sanding and painting them.