Photograph by Fabrizio Bensch, Reuters

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The MakerBot Replicator 2 prints a 3-D sculpture of a human head at the CeBIT computer fair in Germany.

Photograph by Fabrizio Bensch, Reuters

What, Exactly, Is a 3-D Printer?

You can make anything from a pistol to a doll to an airplane wing. Here's how it works.

This week a 25-year-old law student at the University of Texas named Cody Wilson made international headlines when he used a 3-D printer to "print out" a functional .38 caliber pistol.

He then put design software online so that—in theory, at least—anyone in the world who downloaded the software and had access to a commercial 3-D printer and $60 worth of plastic could make their own handgun.

It was a demonstration that not only sparked a lively debate on gun control in the U.S. and abroad, but also threw a spotlight on a vibrant, fast-developing manufacturing technology that could change the shape of the future.

So what is a 3-D printer?

Invented in the mid-1980s, it is a printer that uses plastic, wax, resin, paper, gold, titanium—a whole host of materials—instead of ink to create a solid, three-dimensional object. In much the same way that your desktop printer is directed to print the words in a document, the 3-D printer's jets, guided by computer-assisted design (CAD) software, create an object by spraying or squeezing one thin layer of material at a time onto the platform, then melding them into place with a precisely directed laser. As these microscopically thin layers build up, the desired three-dimensional object slowly takes shape.

While 3-D printing is not a fast manufacturing process, it can be highly efficient because there is virtually no wastage. Unlike traditional manufacturing, where material is cut away by machinery or a lathe to create an object, the "additive" process of 3-D printing uses only what is necessary to make the object. This precision results in a finished product that is both more finely made and up to 60 percent lighter in weight—something of particular interest to the aviation industry.

What can you make with one?

In theory, just about anything. "It doesn't have to be a Saturday Night Special," says Jonathan Rowley, design director at Digits2Widgets, a London-based firm that specializes in 3-D printing. "This technology has plenty of wonderful applications. It can be used for everything from dental work to architectural models, jewelry, precision engine parts, spoilers [the wings for Formula One cars], dolls [with custom faces], sunglasses ... The list is endless."

On a much larger scale Boeing and Airbus are already making numerous small parts using 3-D printing technology, and some have visions of aircraft-hangar-size printers creating huge sections of wing and fuselage. By 2050 entire planes may be made from 3-D "printed" parts.

For the most part, at least at present, 3-D printing is used to make prototypes, to do custom work, or for limited production runs. A major advantage is that the manufacturer doesn't need to spend a lot of money retooling machinery every time the product or specifications change—only the software needs to be modified.

What kinds of materials can the printers use?

Again, just about anything. In Australia researchers are using 3-D printer technology and living cell tissue to try to "print" nerve endings, muscle cells, and cartilage with the hope that someday they can be fused onto human limbs.

Can I do this at home?

Yes and no. The technology has been around for nearly 30 years, and in that time the cost of 3-D printers has dropped dramatically to the point where consumer models are available for as little as $1,200. These home printers, though, are typically used for making knick-knacks and ornaments—stuff that looks, well, rather homemade. Nothing too fancy.

If you are planning to manufacture high-quality goods, like jewelry, you will need to spend considerably more money for a commercial-grade printer. How much? The sky's the limit, depending on what you want to make and the sorts of materials you plan to use. Then of course there is the matter of developing the design and coding the software. And you still need to know a great deal about the physical properties and appropriateness of the materials you are planning to work with.

"It will be a while, I think, before we see a cottage industry flourishing with people making high-quality boutique goods," says Rowley. "But I can imagine such a thing in the future."

As for the white plastic, single-shot .38 that grabbed the headlines this week, that was turned out on a commercial printer that originally cost $30,000 but was bought secondhand on eBay for $5,000. A technological tour de force, perhaps, but there are cheaper and quicker ways to obtain a pistol.