Downtown library Systems Administrator Meg Backus watches a RepRap 3D printer built at home by Jason Brown. The printer was assembled by Brown based on plans shared online via a community of 3-D printing enthusiasts.

The MakerBot Replicator 2 desktop 3-D printer in Company Lab's office builds a nut and bolt out of thermoplastic. The printer head heats a spool of the plastic until it melts then deposits it in layers onto a build platform. Following a pattern guided by a nearby computer, the platform lowers by fractions of an inch as each successive layer is completed.

These chess pieces were made with a 3-D printer at Company Lab.

APPLICATIONS • 3-D printing technology has already made appearances in surprising places, and experimentation suggests future uses could be even stranger: • Students at Washington State University last fall demonstrated that 3-D printing could be used to turn lunar soil into print replacement tools for astronauts. • One of the silver Aston Martin DB-5 sports cars use (and destroyed) in the latest James Bond film, "Skyfall," was actually a 3-D printed replica. • As early as 2011, scientists "bio-printed" cartilage and a silicon "ear." • Bespoke Innovations in San Francisco specializes in 3-D printing custom prosthetic limbs. • Last July, engineers 3-D printed a race car called Areion that could do 0-60 in four seconds and entered it in the Formula Student 2012 challenge. THE PROCESS The MakerBot Replicator 2 desktop 3-D printer in Company Lab's office builds a nut and bolt out of thermoplastic. The printer head heats a spool of the plastic until it melts then deposits it in layers onto a build platform. Following a pattern guided by a nearby computer, the platform lowers by fractions of an inch as each successive layer is completed. GUNMAKING? Last year, 3-D printing technology came under fire from after Defense Distributed, a Texas-based open-source non-profit, announced its intention to create Wiki Weapon, a 3-D printable firearm. In an introductory video on the organization's website, Defense Distributed founder and University of Texas law student Cody R. Wilson says the group intends to perfect the design and upload the schematic to the Internet. There, he says, it can be downloaded for free and manufactured by anyone with a 3-D printer. "Defense Distributed's goal isn't really personal armament. It's more the liberation of information," he says. "As the printing press revolutionized literacy, 3-D printing is in its moment. ... When a 3-D printer can, in theory, be anywhere, so also anything can be produced anywhere. "Anywhere there's a computer, there's a weapon." After crowd-funding site Indiegogo.com ended Defense Distributed's campaign to raise $20,000 to fund its work, the project eventually was funded through donations to its own site in September. Defense Distributed has yet to print off a working prototype, but the group has uploaded videos of successful test firing of 3-D printed magazines for assault rifles.

When people see Mike Bradshaw's 3-D printer in action for the first time, there's usually a rush of in-drawn breath followed by an astonished silence.

Guided by a computer, the print head seems to vibrate as it traces intricate patterns, depositing layers of melted plastic as thin as spun spider silk. At first, the project -- a chess piece, screw or an almost endless variety of other objects -- looks like a formless puddle, but as time passes and the printer's platform descends by increments, it begins to take shape.

Then come the inevitable questions: How does it work? What can it make? Where can I get one?

In Chattanooga, those questions are being answered by a growing community of 3-D printing fans and early adopters of the technology such as Bradshaw, the entrepreneur-in-residence at Company Lab -- or CoLab -- a local small business accelerator.

In late January, Bradshaw installed a MakerBot Replicator 2 in CoLab's Main Street lobby. People's giddy astonishment at the device, he says, is proof that, after decades of being the province of do-it-yourself hobbyists who built their own printers and major manufacturers who bought them for tens of thousands of dollars -- sometimes hundreds of thousands -- 3-D printing has hit the mainstream, with prices dropping as low as about $1,000.

"This is getting real and accessible, and people are starting to understand it," Bradshaw says. "This is when we can get one of these things, put them out here and watch people's eyes get wide."

Layer by layer

Like its 2-D counterpart, 3-D printing begins with a computer file. The blueprint for the finished product starts as a virtual model that the software slices into cross-sections and transmits to the printer. The printer then applies these layers atop each other and binds them together to create an identical replica of the virtual model.

The processes and materials involved vary. Some use UV light to selectively harden a liquid resin. Others, such as the Replicator, melt and extrude metal alloys, wax or plastic from coiled filaments. Spools of the thermal plastics used by these devices currently are available on Amazon.com for $30 to $50 per kilogram.

Some printers have been modified to print using a range of materials, from cement and silicone to cake frosting and cheese. The CandyFab 4000 applies hot air to a bed of low-melting-point materials and can even be filled with granulated sugar to craft edible objects from caramel.

Printing times range from 15 minutes to several hours. Some printers and print methods are faster than others, but generally, the larger and more solid an object is, the longer it will take to complete.

Modern 3-D printing is the brainchild of inventor Charles Hull, who in the mid-'80s developed stereolithography, a process for replicating solid objects from designs stored on a computer. For decades, however, the users of 3-D printers have been a study in extremes.

At the high end were expensive printers that primarily were used for rapid prototyping by manufacturers and universities. On the other end of the spectrum was a devoted community of home-brew builders who designed low-cost, Frankenstein-like machines assembled using plans they shared online. Parts for these machines often could be acquired for $1,000 or less, but the tradeoff was the quality construction and official tech support offered on high-end devices.

In the past three years, however, companies have begun introducing relatively inexpensive, easy-to-construct kits such as MakerBot's Cupcake and MakerGear Prusa 3D. These have been followed most recently by a wave of desktop-size 3-D printers that require no assembly and are designed to work right out of the box. Greater ease of use, plug-and-print functionality and lower sticker prices have resulted in an upswing in 3-D printer sales and popularity in the last two years.

The 3-D economy

In a study released in October, the Consumer Electronics Association named 3-D printing one of five technology trends to watch. According to the study, about 23,000 personal 3-D printers were sold in 2011 at an average cost of $1,132.

That year, the 3-D printing market was worth $1.9 billion, about 290 percent more than in 2010. By 2019, 3-D printing could triple in value to more than $6 billion, according to CEA forecasts.

With the barrier to entry so low, the time is ripe for the public to embrace 3-D printing, says Tim Youngblood, a local developer and business consultant. After watching the industry grow for years, Youngblood says he was convinced to buy his MakerBot Replicator last spring, when the price dipped below $2,000.

If 3-D printing continues to grow in popularity, Youngblood says, its impact could be as revolutionary as echo the micro-processing revolution of the '80s that made PCs a household fixture.

"To see [3-D printing] work and happen and then hold something in your hand ... really is a liberating moment," he says. "You can see the wheels turning in people's heads. "It's a new way of thinking about how we make things, and it's a technology that is going to be extremely disruptive over the next few decades."

The ability to print almost any object raises inherent questions about the sanctity of intellectual property. On the online schematic library Thingiverse, for instance, models are available for functional LEGO blocks, pieces for the "Settlers of Catan" board game and replicas of Star Wars characters. The terms of use agreements for most virtual 3-D printing storefronts, however, have clauses prohibiting the upload of copyrighted content.

What's next

Some companies have taken advantage of 3-D printing to set themselves up as micro-manufacturers.

In contrast to traditional production methods, in which products are produced on a massive scale to please a large audience, 3-D printing's proponents say the technology has led to the advent of small-scale production of hyper-customizable goods.

Last summer, Ooltewah resident Willie Spurgeon bought a MakerBot Replicator and established Chattanooga 3-D Printing with his friend, Shane Burrow. Spurgeon owns a sign company, but he says he wanted to build a second company around contracting out the printer to create cheap prototypes for area businesses.

So far, however, being one of the first companies in the area to offer the services of a 3-D printer has been a double-edged sword.

"Most people can't fathom it," he says. "It's almost like 'The Jetsons'-type stuff, futuristic stuff that wasn't supposed to happen yet."

Stimulating thought about that potential is why Bradshaw decided to install the MakerBot in the middle of CoLab's lobby where everyone could see it.

"Our mission in this and the reason I thought this was a good place for this to land is to stimulate people's thoughts about a forward-looking technology," he says.

Uses for the technology are becoming increasingly diverse. In October, the 3D Print Show in London showcased a collection of 3-D items that included the world's first 3-D printed bikini, 3-D printed shoes, guitars and replicas of Egyptian mummies.

"Walking around the show today, you can literally see the birth of a revolution," says futurist and video blogger Christopher Barnatt in a video for his website, ExplainingTheFuture.com.

Encouraging interest in 3-D printing and preparing people with the skills to participate in an economy driven by the technology is a key goal of the downtown library, says Meg Backus, the systems administrator for the Public Library system.

Backus says the plan is to install at least one 3-D printer as part of an effort to turn the library's now-empty fourth floor into a "big creation lab." What people do with it is up to them, but the goal is to familiarize them with the technology, she says.

"The whole idea of the 3-D printer is whiz-pop, cool technology, but the underlying principle of it is that it democratizes manufacturing," she says. "The biggest thing right now is just getting the technology accessible so people can start learning to design things for it on the computer."

On March 16, CoLab, the library and other local organizations will collaboratively host a meet-up for local 3-D printers and have begun discussions to organize a "Maker Fair" for spring 2014 to showcase the work of local 3-D printers.

At the moment, 3-D printing may be flying mostly under the radar, but Bradshaw says that's changing with every printed object he puts in someone's hands.

"When I print one of these things and give them to someone, I call them 'souvenirs from the future,'" Bradshaw says. "It literally gives me chills to think ... that whole Star Trek-y thing is coming onto the page right now, right in front of our eyes."