You feed them a blueprint that you've designed, and out comes a three-dimensional object. But what if you don't know how to design a blueprint on the computer? That's Okay because there are a lot of free designs, right on the Web. You can go to thingyverse.com or cubify.com and look for thousands of designs.
You'll find ready-to-download designs for everything from chess pieces to garden toads. Once you've downloaded the blueprint and set up the printer with a roll of material, you're good to go.
You do need a little bit of patience if you're going to print with a 3D printer because you're feeding a roll of plastic or some other material, and it extrudes that material, layer by layer, to build your object. So even building something small can take hours.
For now, the machines are really for hobbyists, DIY enthusiasts, and people who are really captivated by this idea and want to play with it. The printers are not super-practical yet. Right now they cost too much money to be a household item.
Though Consumer Reports says it might be a while before 3D printers go mainstream, many industries are already using them. For example, car companies create prototypes of engine parts with 3D printers and dentists make retainers and mouth guards.