How to Build 3-D Printing

3-D printing—or additive manufacturing, as it is sometimes called—builds parts by depositing layers of metals, thermo­plastics, and even ceramics in a design dictated by a computer file. The technology, which can create complex things that are difficult to manufacture traditionally, has been used to print highly customized products like hearing aids and parts for airplane engines.

It is already well accepted by a few companies. Align Technology uses it to make Invisalign dental braces designed for individual patients, and the aerospace industry uses additive manufacturing to create some high-tech parts. General Electric, one of the world’s largest manufacturers, has developed a 3-D-printed fuel nozzle made from a mix of cobalt, chrome, and molybdenum. Included on our 2013 list of 10 Breakthrough Technologies, it has fewer parts and is 25 percent lighter and five times more durable than previous nozzles, the company says.

But beyond these few early adopters, the technology’s appeal has been limited by its high cost and slow speed. For 3-D printing to become more widely used, the overall process will need to be cheaper, and the machines will need to be redesigned to make it faster and support a wider array of materials.

“It is still a market that is quite expensive,” says Dominik Rietzel, an additive-technologies specialist at BMW Group Research and Innovation Center in Munich. While 3-D printing can save on the amount of material needed to make a part, preparing and formulating materials for the machines can be expensive, and the results are not always consistent. As a result, traditional injection molding remains more economical for high-volume part production, says Rietzel. BMW, which has invested substantially in 3-D-printing metals and plastics since buying its first additive-manufacturing machine in 1989, uses the technology for rapid prototyping and to validate manufacturing processes for new car designs, not to mass-produce parts. The cost of the machines and materials would need to be reduced “significantly” before the company would consider that, according to the automaker, which made more than two million cars last year.

Researchers are working to reduce the expense of getting bulk metals and plastics into a form that can be processed with a 3-D printer. Others hope to find ways to eliminate the need to change their form.

Metalysis, based in Rotherham, U.K., says it has developed a way to significantly reduce the cost of 3-D printing with titanium, which is valued for its light weight and strength. Unlike traditional machining, which can use titanium in its natural state, additive manufacturing requires the metal to be turned into a powder. That process is expensive. Using a method based on research from the University of Cambridge, Metalysis is able to create titanium powder for as little as 25 percent of the cost of the usual process.

The U.S. Department of Energy’s Oak Ridge National Laboratory, in Tennessee, is working to develop a machine that can print with high-­performance plastics already commonly used in traditional manufacturing. A gantry-style machine, which could be commercialized as early as 2015, uses thermoplastic pellets reinforced with glass and carbon fiber. Widely used in the injection molding industry, these pellets cost just $1 to $10 per pound, and the Oak Ridge printer can use them to produce things as diverse as affordable tooling and unmanned aerial vehicles. There is an added benefit: testing has shown that putting these materials through an additive-­manufacturing process actually makes them stronger and stiffer by aligning the carbon fibers, says Lonnie Love, a research scientist at the lab.

Besides cost, speed is another obstacle 3-D printing must overcome to be useful in mass production. The systems still generally make parts at only about one cubic inch per hour, says Love, which means it could take days or weeks to make a part the size of a shoebox. But the new machine from Oak Ridge will be able to print parts 200 to 500 times faster. The downside: the surface finish suffers, and parts must go through a traditional machining process to give them their final look.

Google’s Project Ara, which plans to print customized cell-phone parts by 2015, is also pushing for speed. Its supplier, 3D Systems, the first maker of a commercial 3-D-printing machine, has rethought its basic approach. Its new printing process involves an assembly line on which parts move around a track and are built up by fixed print heads above. 3D Systems says this approach has already beaten injection molding speeds.

Beyond speed and cost, manufacturers face one more challenge: perfecting the composition of the materials to give them the strength and versatility needed for industrial applications. NASA’s Jet Propulsion Laboratory in Pasadena, California, working with the California Institute of Technology and Pennsylvania State University, is using lasers to melt metal powders to form alloys that are then deposited onto a rotating rod layer by layer. The process could allow manufacturers to switch between two different alloys during production and make parts from more than one metal.

“We’re learning how all the interactions of machine and material play together, how they form not only the shape but also the properties,” says ­Christine Furstoss, GE’s manufacturing and materials technology director.

“Forming the properties at the same time you’re making a shape—it’s something that took the forging and casting industry decades to figure out,” Furstoss adds. “We’re trying to do it in years.”