It sounds like the promise of an ad in the back of a PopSci issue from the 1950s. Build your own replicating machine! Make anything you desire in your own garage! But that’s exactly what veteran hacker Bre Pettis and his pals offer with their CupCake CNC kit: a computer-controlled 3-D printer that can whip up almost any object of less than four inches on a side from two kinds of plastic. The company’s goal is to make home manufacturing cheap and common. And the whole setup is open-source, so anybody can modify and improve the design, or even copy it wholesale.