Kirk Phelps wants to change how things get made. He holds up a floppy yellow circle of plastic, a sealing gasket for a generic automotive engine, and explains how this gasket is limiting human creativity. “If you want to make a new kind of engine, you don’t get to design the engine from the ground up. You actually go to your gasket supplier and ask what standard gaskets are available and you design the engine around it. This is backward,” says Phelps, a 33-year-old product designer who helped develop the multitouch on the first iPhone. That frustration led him to take the job as head of product development at Carbon3D, one of the hottest startups to come along in the emerging 3-D printing industry. The promise of 3-D printing is the ability to produce a solid part on the spot based on any digital 3-D file, freeing engineers to build their dream engine. While some of the highest-end machines can precisely print small-batch items such as hearing aids and artificial joints, the va...