It’s rare that a gleaming, azure legend on wheels fails to turn heads, but at the Detroit auto show earlier this month, Oak Ridge National Laboratory’s Shelby Cobra faced stiff competition for attention.
Acura and Ford introduced their new supercars, while other automakers presented next-generation hybrids and electrics. Towering matte military fighting vehicles and shiny trucks vied for the eyes of more than 800,000 attendees.
But in this showcase all about the future of the auto industry, the Oak Ridge Cobra, a throwback to 1967, was a harbinger of things to come.
The polished paint and chrome belied bodywork that came out of a 3-D printer, making the roadster a victim of its own success.
"People would walk by it and say, ‘We don’t get what’s going on,’" said Lonnie Love, group leader for the manufacturing systems group at Oak Ridge.
It wasn’t until Love placed a sign on the windshield saying "Yes, it’s a 3D printed car" that more people stopped to check it out.
The project was a proof of concept, showing the potential of additive manufacturing in the automotive industry. Rather than milling away a block of metal, a printer creates a component from the bottom up, adding to it layer by layer from a print head.
Using these techniques, automakers can cut development time, shrink the carbon footprint of their production cycle and tailor their vehicles for specific markets.
"We set out to develop technologies that could really push the envelope of a printed vehicle," Love said.
A fraction of the parts, all of the speed
Over the course of six weeks, researchers printed the chassis and bodywork for the Cobra from carbon fiber reinforced polymers. While a production car can have more than 20,000 parts, the Oak Ridge roadster had fewer than 70 and weighs about 1,600 pounds.
"Literally, you could put a whole new drivetrain in in a couple days," Love said. "The whole car, in terms of manufacture, was extremely cheap." The price tag came out to about $14,000, he added.
Though the Oak Ridge Shelby Cobra traded the throaty rumble of a V-8 for the purr of a 100-kilowatt electric motor, it could still lay rubber, going from zero to 60 mph in less than five seconds. The motor, drivetrain, brakes and wheels came off the shelf.
"It’s really exciting what Oak Ridge is doing because it shows us that we can take this to a much larger level," said Ellen Lee, team leader for additive manufacturing research at Ford Motor Co. "It’s really beautiful," she said of the Cobra.
Automakers have used additive manufacturing techniques in some form for the past 30 years, but printing was largely limited to one-off parts used only in the design and prototype stage.
"It’s really tough today to compete with manufacturing processes like injection molding and stamping," Lee said. Though the machines that produce parts like doors, bumpers and chassis take months to set up and cost millions of dollars, they make components in seconds, which is essential for factories that crank out a half-million cars at a rate of one per minute.
Additive manufacturing, on the other hand, can take hours per part. There are also potential structural problems: Parts are printed in successive layers, so they may withstand stress in one dimension but fracture when bent a certain way.
Shorter production time using less energy
The printing process also leaves ugly scalloped edges. The Oak Ridge Cobra required extensive sanding and smoothing to match the curves of the classic.
For a large manufacturer like Ford, the value of 3-D printing comes further upstream in designing cars and the tooling needed to manufacture them.
Rather than restructure an entire assembly line, engineers can test fit parts in a limited production run, fix problems and print again.
"By using these technologies in the prototypes phase, you can iterate though designs without changing the tooling," said Harold Sears, an additive manufacturing technical specialist at Ford.
This speeds up the product cycle from something that spans years to a few months, allowing new car designs to hit highways faster.
In addition, instead of competing with molds and stamps, engineers can use 3-D printing to make the tooling itself. Sears explained that much of the tooling used to make car parts for a specific model is milled from steel and aluminum, an expensive, time-consuming, energy-hungry process. For a prototype or a limited production car, this is overkill, and it expands the energy footprint of a production line.
With a 3-D printer, engineers can develop custom tools in hours, designing components with strategically placed internal pockets to reduce weight and the amount of material used, something that’s impossible to do with conventional machining processes. Reducing the energy used in production creates a more favorable footprint for clean technologies like electric and fuel-cell cars, shrinking the environmental payback time.
New automakers, however, are looking to take additive manufacturing further. Lawrence Gasman, president of SmarTech Markets Publishing, a 3-D printing research firm, observed that 3-D printing lowers the barriers to entry for automotive suppliers and companies building cars at smaller scales. "It’s going to lure more entrepreneurs into the business," he said.
‘Microfactories’ curbing expenses
One such company is Local Motors, based in Phoenix, Ariz. The company printed its own car, the Strati, on the floor of the Detroit auto show. The company aims to build customizable cars at "microfactories" around the country.
Justin Fishkin, chief strategy officer at Local Motors, said his interest came from wanting to build fuel-efficient cars for climate change-conscious island communities.
"I couldn’t find any auto manufacturer in the world interested in making 50,000 units," he said. "The volume wasn’t big enough for them. It seems like a lot of cars to me, but it didn’t move the needle."
Using crowdsourced designs, the company aims to give car buyers more control over their vehicles. Fishkin said he envisions a dealership resembling an Apple store, where a customer comes in, picks the features he or she wants on a computer and then picks up the printed car the next day.
This approach lets the company hedge between different clean technologies. "What we’re doing with this digital platform is we’re allowing the consumer to choose what fuel they want to run on," Fishkin said.
In a region like the Eastern Seaboard, where electric vehicle chargers are more prevalent, a customer may select an electric drivetrain. In an area with hydrogen stations, a buyer may want a fuel cell. Others may prefer a gasoline hybrid.
Using 3-D printing, Local Motors can accommodate all of these choices without having to build a massive plant for each version. And with a microfactory in every region, the transportation and delivery expenses of a car go down, shrinking its carbon footprint.
When the car is traded in, Local Motors can recycle it and give the customer a credit toward a new vehicle. The company already has factories in Phoenix and Las Vegas, with planned facilities near Washington, D.C., and Knoxville, Tenn.
Earlier this month, President Obama announced that the University of Tennessee would lead the Institute for Advanced Composites Manufacturing Innovation, a $259 million research consortium, with 122 members, including Oak Ridge, Ford and Local Motors (Greenwire, Jan. 9). The goal is to produce materials for lighter cars, stiffer wind turbine blades and cheaper gas storage tanks.
As a result, according to Oak Ridge’s Love, interest in 3-D printing is growing and the science is rapidly advancing.
"It’s a rocket taking off," he said.