Layer by Layer: 3-D printing
The parts in jet engines have to withstand staggering forces and temperatures, and they have to be as light as possible to save on fuel. That means it’s complex and costly to make them: technicians at General Electric weld together as many as 20 separate pieces of metal to achieve a shape that efficiently mixes fuel and air in a fuel injector. But for a new engine coming out next year, GE thinks it has a better way to make fuel injectors: by printing them.
To do it, a laser traces out the shape of the injector’s cross-section on a bed of cobalt-chrome powder, fusing the powder into solid form to build up the injector one ultrathin layer at a time. This promises to be less expensive than traditional manufacturing methods, and it should lead to a lighter part—which is to say a better one. The first parts will go into jet engines, says Prabhjot Singh, who runs a lab at GE that focuses on improving and applying this and similar 3-D printing processes. But, he adds, “there’s not a day we don’t hear from one of the other divisions at GE interested in using this technology.”
These innovations are at the forefront of a radical change in manufacturing technology that is especially appealing in advanced applications like aerospace and cars. The 3-D printing techniques won’t just make it more efficient to produce existing parts. They will also make it possible to produce things that weren’t even conceivable before—like parts with complex, scooped-out shapes that minimize weight without sacrificing strength. Unlike machining processes, which can leave up to 90 percent of the material on the floor, 3-D printing leaves virtually no waste—a huge consideration with expensive metals such as titanium. The technology could also reduce the need to store parts in inventory, because it’s just as easy to print another part—or an improved version of it—10 years after the first one was made. An automobile manufacturer receiving reports of a failure in a seat belt mechanism could have a reconfigured version on its way to dealers within days.
Additive manufacturing, as 3-D printing is also known, emerged in the mid-1980s after Charles Hull invented what he called stereolithography, in which the top layer of a pool of resin is hardened by an ultraviolet laser. Various methods of 3-D printing have become popular with engineers who want to create prototypes of new designs or make a few highly customized parts: they can make a 3-D blueprint of a part in a computer-assisted design program and then get a printer to spit it out hours later. This process avoids the up-front costs, long lead times, and design constraints of conventional high-volume manufacturing techniques like injection molding, casting, and stamping. But the technology has been adapted to only a limited set of materials, and there have been questions about quality control. Building parts this way has also been slow—it can take a day or more to do what traditional manufacturing can accomplish in minutes or hours. For these reasons, 3-D printing hasn’t been used for very large runs of production parts.
But now the technology is advancing far enough for production runs in niche markets such as medical devices. And it’s poised to break into several larger applications over the next several years. “We’ve come to the point when enough critical advances are happening to make the technology truly useful in manufacturing end-use parts,” says Tim Gornet, who runs the Rapid Prototyping Center at the University of Louisville.