It might be the future of manufacturing, but 3-D printing is built on a 2-D foundation: A MakerBot is essentially an inkjet printer that spits out plastic instead of ink. Keep printing in the same spot, over and over, and the layers will eventually form a 3-D object from the bottom up. But an outfit called Carbon3D is taking the opposite tack: Its new rig creates objects from the top down, in one continuous motion. It’s faster and eliminates the layering that can result in weak, jagged objects.
Inspired by the mercurial T-1000 bot from Terminator 2, University of North Carolina professor Joseph DeSimone wanted to make objects emerge from liquid. The process is based on a 30-year-old printing technology called stereolithography. It starts with a bath of liquid resin that hardens when exposed to UV light. A projector underneath delivers targeted blasts of UV to shape the form from below as the overhead platform lifts, drawing the object out of the soup.
The method has some limits. Oxygen inhibits the chemical reaction that solidifies the resin, slowing the process somewhat. But rather than fighting that limitation, DeSimone harnessed it. A sheet of glass between the projector and the resin is gas-permeable like a contact lens, and the oxygen keeps the resin from hardening too soon, before the object is complete.
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