Google's modular Project Ara smartphone is all about customization, but that creates a challenge: how are manufacturers supposed to build so many uncommon (and possibly unique) parts? The crew at 3D Systems is more than happy to tell you -- it just outlined the 3D printing techniques it's using to make Ara a reality. The company is dropping the conventional printing process, which bogs down due to frequent changes in speed, in favor of a continuously moving system that's fast enough to cope with mass production. The technique should generate "millions" of parts, even when some components need special treatment.The manufacturing technique should be very flexible, to boot. We already knew that 3D Systems would be making conductive ink (with the help of Carnegie Mellon University and X5 Systems) to print working parts, like antennas. However, it will also print parts in a "full spectrum" of colors, including transparencies; there's a possibility that you'll get parts for your Project Ara phone in the exact hues you want. You'll still have to wait until 2015 to get a modular mobile device of your own, but you'll at least know how it came into being.