By Dan Carney

When we talk about speed with regards to the auto industry, we're usually talking about zero-to-60 acceleration. But what about zero-to-market? That's where 3D Printing is revolutionizing the industry: How quickly car companies can design, test, and produce new vehicles.

Think of all the specialized pieces that go into a functioning automobile—then imagine trying to find those parts for car models that don't yet exist. Increasingly, big-name manufacturers like GM and Jaguar Land Rover are using 3D Printing whenever they need those specialized parts in a hurry. The technology rapidly reduces the time needed to build customized parts used in aerodynamic testing and preproduction prototypes, and it's ideal for creating molds used to mass-produce a slew of parts used in actual production vehicles.

This capability has sparked talk of "printed" cars, and while printing your ride might be an interesting demonstration of the technology's maturity, it wouldn't result in a car many people would want to drive. According to Lee Dockstader, vice president of business development for 3D Systems, the ABS (acrylonitrile butadiene styrene) plastic body parts that can be printed would likely be non-structural items like fenders, hoods, trunk lids, and door skins, as opposed to frame rails, floor pans, and other components that need to be crash-absorbent. Furthermore, printed cars would be stylistically limited, because printed ABS plastic doesn't allow for distinctive feature details like creases and lines.

Instead, 3D Printing machines, which cost carmakers between $500,000 and $1 million per unit, are mostly used today to make molds for plastic trim, brackets, air intake hoses, and various "under-hood" components—commonly referred to as "black plastics"—when the time comes to mass-produce these parts via traditional injection molding.

They're also used to solve the paradox of building a preproduction prototype vehicle: How do you outfit a new vehicle with the brackets, hidden ventilation hoses, and various instrument panel components when those parts haven't ever been manufactured? A prototype for a new air dam would take a week to create using traditional methods, but with 3D Printing, that process is cut down by more than half. This means a manufacturer can build the part, install it onto the prototype for testing in the wind tunnel, and decide whether to move forward or not, twice as quickly. A sidebenefit of this approach is that it gives factory workers parts to use while they learn to build the new model.

While parts printed for these applications can also serve to make the molds for high-volume injection molding, the notion of replacing injection molding in production remains a bit overheated.

"[3D Printing] will never beat injection molding for high-volume manufacturing," says Dockstader, who adds that injection molding machines produce parts faster and cheaper once the tooling is paid for.

This probably means that the technology will be limited to small production runs, as Dave Bolognino, director of GM design fabrication operations, explains.

"We believe direct digital manufacturing will have a significant role in small volumes," he says.

Of course, "small volume" is a matter of definition. According to Bolognino, GM's rapid prototyping equipment annually cranks out roughly 20,000 printed parts for use in testing, preproduction, and molds. For now, this means cheaper, faster R&D, and ultimately, cheaper, better cars.

Manufacturers will likely shift production of printed parts into a higher gear once 3D Printers become better at combining two or more materials to make a finished product.

Dan Carney writes for MSNBC.com, Popular Mechanics, Automotive Engineering International, and AutoTrader.com, and has contributed to The New York Times, The Wall Street Journal, Motor Trend, Truck Trend, Popular Science, Better Homes and Gardens, Racer, Racecar Engineering, AutoWeek, Sports Car International, European Car, and Motorcyclist among others.