More design hobbyists, entrepreneurs use 3-D printing

— -- Matt Sullivan, a retired soldier, still has trouble explaining his right leg to strangers.

The shiny chrome surface, embossed with the lightning bolt logo of his beloved San Diego Chargers, covers the calf area of his prosthetic leg, the result of a roadside bomb in Afghanistan in 2010.

At the naval hospital where he was recovering from his wounds and the resulting surgery, Sullivan ran into entrepreneur Scott Summit, who suggested a solution to covering the metal rod that protruded conspicuously from his knee.

Summit's firm, Bespoke Innovations, uses an obscure process known as 3-D printing to make durable thermoplastic leg coverings, or fairings. By digitally scanning the surviving leg to match its shape and form, Bespoke produces curved panels resembling soccer shin pads that cover the artificial limb. You can often tell a person has a prosthetic leg by the way the pants leg flaps, Sullivan says. "Having that symmetry now, you can't tell the difference."

Thanks to the Internet and declining hardware costs, 3-D printing — once a specialized process used sparingly by industrial companies for prototyping — is becoming more common among design hobbyists and entrepreneurs such as Summit.

The consumer market's embrace of the technology has been swift. Sales for all 3-D printing products and services worldwide grew 24% to $1.33 billion in 2010, fueled in part by a fast-growing market of do-it-yourselfers, says industry research firm Wohlers Associates.

The firm also estimates sales will continue to post "strong double-digit growth" in the next several years, reaching about $3.1 billion by 2016 from an estimated $1.6 billion this year.

Here's how 3-D printing generally works: Once a product is designed on software, the file is sent to a special 3-D printer that contains a spool (or cartridge) of a material — typically, plastic, metal or ceramics — in a fine powder or gel-like texture. Like printing on paper, the 3-D printer lays down successive layers of the material and builds up until an object emerges. It's then cleaned, painted or cooled.

"It's like a hot glue gun. Think of it as building from strings of spaghetti glue," explains Jim Kor, a Canadian engineer who has printed the exterior panels of a fuel-efficient concept car, the Urbee, with the help of Stratasys, a Minnesota company that is a 3-D printing technology pioneer.

Traditional manufacturing, involving injection molding or die casting, generally produces better results for making parts in large volumes. Experts caution that 3-D printers, particularly entry-level models, can produce rough finishing and imprecise details, and raw materials may be expensive.

But proponents say the technology enables on-demand parts production, eliminates assembly lines, reduces inventory and is a speedier process for making objects or parts that don't require precise detailing.

The technology is already prevalent in industrial manufacturing. Boeing prints some air duct parts for its planes. Invisalign's teeth aligners are printed, as are hearing aid shells by Starkey Laboratories in Minnesota.

"You have freedom of creation. You can do almost anything," says Terry Wohlers of Wohlers Associates.