PASADENA, Calif. — Sometimes a particular piece of plastic is just what you need. You have lost the battery cover to your cellphone, perhaps. Or your daughter needs to have the golden princess doll she saw on television. Now.

In a few years, it will be possible to make these items yourself. You will be able to download three-dimensional plans online, then push Print. Hours later, a solid object will be ready to remove from your printer.

It’s not quite the transporter of “Star Trek,” but it is a step closer.

Three-dimensional printers have been seen in industrial design shops for about a decade. They are used to test part designs for cars, airplanes and other products before they are sent to manufacturing. Once well over $100,000 each, such machines can now be had for $15,000. In the next two years, prices are expected to fall further, putting the printers in reach of small offices and even corner copy stores.

The next frontier will be the home. One company that wants to be the first to deliver a 3-D printer for consumers is Desktop Factory, started by IdeaLab, a technology incubator here. The company will start selling its first printer for $4,995 this year.