By Catherine Bolgar
The aerospace industry is leading innovation in additive manufacturing on several fronts, including applications, materials, processes and design.
Additive manufacturing (AM), also known as 3D printing, may be well-suited to the aerospace industry, as long as the technology is certified and the cost comes down. This industry needs to make complex parts in low volumes from high-performance materials, while constantly seeking new ways to lower costs. While AM can cost more than traditional machining methods, it provides savings on materials—which can be substantial when using expensive metals such as titanium.
“There has recently been a real tectonic shift in the way large aerospace companies are investing in additive manufacturing,” says Kamran Mumtaz, lecturer in additive manufacturing at the Centre for Advanced Additive Manufacturing at the University of Sheffield, U.K.
Here are some areas of innovation:
AM originally was used to make plastic models and prototypes for basic form and fitting applications, but not for functional testing. Then AM was used to make plastic parts for functional applications. “More recently, it has been used for brackets, ventilation ducts and parts to hold wires and cables in place,” says Terry Wohlers, president of Wohlers Associates, a Fort Collins, Colorado, AM consulting firm. “Now, more parts are being made of metal AM, and I have seen no fewer than 25 new and innovative designs from one major aerospace company, alone,” he says.
“With traditional manufacturing, many parts must be assembled from smaller pieces, because of the limits on what shapes can be cast, milled or molded,” Mr. Wohlers explains. “The technique of building in layers allows for parts to be combined digitally that could include 20, 50 or 100 parts into one, two or three parts,” he says. Fewer parts means big savings in expensive manufacturing processes, assembly, labor, inventory and maintenance, he says, adding that companies also are seeing a reduction in certification paperwork, because each part must conform to the strict requirements of regulatory agencies.
Polymers, or plastics, are the most mature technology, but titanium 6-4, which can be difficult to grind or weld, is the most popular because of how well it works in AM, along with aluminum, nickel, stainless steel, and cobalt chrome.
New materials would require going through a qualification process, which takes several years. However, researchers are looking at feed stocks, optimal particle sizes and recyclability of leftover powder, says Bill Peter, director of the Manufacturing Demonstration Facility at Oak Ridge National Laboratory in Oak Ridge, Tennessee.
The laboratory recently made the largest 3D-printed component, which wasn’t a plane part but a trim tool to make the extended wing section of the new Boeing 777X. Traditionally made of metal, the AM tool was made of a composite of polymers with chopped carbon fiber. The AM tool is faster and cheaper to make than a metal one, Dr. Peter says.
Work is being done on AM composites that can withstand high pressures and temperatures as high as 176°C (350°F). “It would have tremendous savings for tooling in the composite industry for air applications,” he says. “Eventually, we want to understand how to bring the best materials to a problem set and come up with hybrid solutions,” using metals, polymers and ceramics.
AM makes it possible to alter microstructures as the materials are processed, which can affect their strength and flexibility. For example, one AM company “can blend two or more polymers and, consequently, can make one location of a part rigid and gradually transition to soft and elastic in another location,” Mr. Wohlers says.
The most common AM method for making metal parts is to lay a bed of powder and to melt it, layer by layer, with a laser or an electron beam, following a programmed design. However, the AM machines remain limited in size, so most of the parts made are small and in limited volumes.
“At Sheffield, we’re developing new manufacturing processes that improve on efficiency, build speed and enhance the properties of the components,” Dr. Mumtaz says. “We have a metallic-powder-bed manufacturing process, called diode-area melting, or DAM, that has the potential to be 10 times faster than conventional selective laser melting.”
Selective laser melting uses a single laser. Increasing speed requires a more powerful laser or integration of multiple lasers. “DAM replaces a single-point laser with up to 20 laser diodes. You can scan an entire powder bed faster,” he says.
Topology optimization is the mathematical technique employed to find the best way to “use minimal materials and minimal weight, but fulfill the needs of the part,” Mr. Wohlers says.
When grinding a part, 80% to 90% can be scrap. Additive Manufacturing is the opposite of that: you can do a highly convoluted, complex shape that can reduce materials and weight by 40% to 50% sometimes.”
INTERNET OF THINGS
AM machines are equipped with cameras and sensors to track the fabrication, point by point, including in the middle of a part as it’s being formed. “We’re capturing the information and using data analytics to see what’s going on,” Dr. Peter says.
Eventually, manufacturers would like to incorporate sensors into the parts, to monitor them for temperature, humidity, vibration or other data. However, sensors and metal or polymers are “dissimilar materials—and that makes things complicated,” Dr. Peter says. “While research activities are stepping up in the area of embedded sensors, there is a need for continued research to commercialize.”
Catherine Bolgar is a former managing editor of The Wall Street Journal Europe, now working as a freelance writer and editor with WSJ. Custom Studios in EMEA. For more from Catherine Bolgar, along with other industry experts, join the Future Realities discussion on LinkedIn.
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