Wisconsin Precision Casting makes metal parts that go into larger objects. Think lawnmowers, hospital gurneys, boat propellers, hand tools. Its customers range from independent designers to the big boys: Caterpillar and Deere.
Based in East Troy, Wis., the small business had been operating for nearly 50 years within America's Rust Belt, which includes manufacturing-heavy states from New York to Wisconsin.
Then, about eight years ago, co-owner Cliff Fischer encountered a 3-D printer for the first time.
"When I saw a 3-D drawing of a part and I watched it being produced in front of my eyes in a short time, I said, 'We've got to jump on this,' " he said. "It's going to revolutionize our industry."
Today, Wisconsin Precision uses 3-D printers to "print" metal objects. The fast-evolving technology, sometimes called additive manufacturing, lets them create custom prototype molds and finished products in weeks instead of months. Its new customers include juice-machine makers and model-train enthusiasts.
An industry secret for years, 3-D printing is spreading quickly to the masses. Amazon has unveiled a dedicated section for 3-D printing, including desktop models from Brooklyn, N.Y.-based start-up MakerBot. (Amazon founder Jeff Bezos is among its investors.) And anyone can buy a 3-D printer from Staples.
There's no shortage of provocative ideas. NASA is developing 3-D pizza for astronauts. Defense Distributed, a nonprofit digital publisher, is focused on printable gun components.
(Read More: 10 Ways 3-D Printing Will Blow Your Mind)