By Melissa Donovan
Similar to other industries, three-dimensional (3D) printing in aerospace/aeronautics continues to gain in popularity. The demand for more efficient manufacturing processes is real and additive manufacturing (AM) is one way to meet increasing requirements for faster turnaround times while maintaining a quality—and safe—product.
Robust 3D printing technologies paired with durable materials lend themselves well to not only prototypes and tooling, but the final parts. Metal, polymers, plastics, and even ceramic are found in production facilities worldwide to create anything from a jig, fixture, or mold to a cabin filter or turbine blade. Both one-off pieces as well as multiple parts on a production level are produced.
Above: These topologically optimized large brackets created with 3D Sytems’ DMP technology are 25 percent lighter, have a better stiffness-to-weight-ratio, and were completed for Thales Alenia Space in half the time it would have taken with a traditional manufacturing process.
The Ideal Opportunity
3D printing is ideal for creating parts used in the aerospace/aeronautics sector. Lower part volumes, the need to heighten efficiencies—reducing lead times, and weight are all critical factors as to why those in this segment utilize 3D printing.
“The aerospace sector demands shorter lead times, high customization, and cost efficiency both for cabin interior parts, other in-flight applications, and ground engineering and maintenance. 3D printing meets all of these key requirements. In aerospace applications, it’s an added-value technology, because it’s a faster, customized production method that optimizes repairs and lightweight designs,” shares Martin Black, managing director, BigRep GmbH.
Addressing volume, Scott Killian, aerospace business development manager, EOS, cites that the aerospace industry requires much lower part production than other industries. “One engine type may number in the tens of thousands instead of the hundreds of thousands. Therefore, AM has a bigger opportunity to keep up with those volume demands at a cost-competitive rate.”
“If a manufacturer is producing massive numbers of components, then tooling costs can be spread across them and do not have a big impact. AM is highly effective at lower volumes because it allows for production without tooling,” agrees Scott Sevcik, VP, aerospace business segment, Stratasys Ltd.
These smaller volumes are linked to increases in efficiency and reduction of lead times. “Especially for expensive materials and alloys like titanium, certain AM technologies drastically improve buy-to-fly ratios and as lot sizes are limited lead times are as well,” explains Tobias Röhrich, CEO, Gefertec GmbH.
“3D printing significantly reduces high delivery costs and long lead delivery times typically tied to replacing parts. In the aerospace industry, the ability to efficiently create on demand, custom-made parts that are unique to individual aircrafts on site is extremely valuable,” comments Paul Heiden, SVP product management, Ultimaker.
In addition to the parts, the tools used in the process are able to be printed with AM. According to Heiden, aircraft parts are difficult to work with using off-the-shelf tools. 3D printing allows for tailored tools to be cost-effectively created for these unconventional parts.
A major factor in aerospace/aeronautics is weight. “Aerospace manufacturers are focused on reducing weight, sometimes doing complex things to shave a few pounds from an aircraft. They pursue every advantage they can find from a technology standpoint,” shares Sevcik.
Weight reduction affects multiple parts of the process. Melanie Lang, co-founder/CEO, FormAlloy, suggests that by joining increased efficiencies and reduced weight, 3D printing has a positive influence on the environmental impact of air travel. “The results can be higher thrust capabilities and reduced fuel consumption,” she continues.
“The biggest challenge is reducing the weight of the aircrafts, while keeping the performing standard of the produced parts at a high level,” admits Ilaria Guicciardini, marketing director, Roboze. 3D printing allows for durable parts that weigh less—providing manufacturers with the best of both worlds.
Ethan Baehrend, founder/president/CEO, Creative 3D Technologies, explains that while 3D printed parts reduce weight, they still maintain or exceed the original part’s effectiveness. “Part strength and weight are crucial and creating parts that are more conscious of both by not being constrained by traditional manufacturing methods is a game changer,” he says.
Traditional manufacturing methods are limited by material selection compared to 3D printing. Jonah Myerberg, CTO/co-founder, Desktop Metal, Inc., provides the example of alloys—which are able to deal with high heat and as a result can be used for parts placed near jet engines. These are typically not found in traditional manufacturing methods.
“Ceramic printing is especially exciting for high-temperature electronics and heat exchangers, and high wear applications for fuel, coolant, and combustion systems. AM enabled designs have the potential to produce significant efficiency improvements,” adds Shawn Allan, VP, Lithoz America, LLC.
Parts for Play
Traditionally, the aerospace and aeronautics industr relied on 3D printing technologies for a host of non-critical features like interior décor and caps and braces to hold pieces together. As new 3D printing processes are introduced—and coincidentally new materials—this is constantly changing.
Killian says that historically, common 3D parts in the aerospace industry were found in the body of the plane. For example air ducting. “This was formed from a carbon fiber layup, utilizing AM manufacturing with plastics polymer materials to allow for better design customization and part consolidation, specifically in planes with unique cabin space constraints.”
Metal 3D printers enable the production of parts like rocket nozzles, blades, fuel nozzles, and landing gear brackets, according to Lang.
“A range of parts are possible including structural components like brackets and non-structural components like ducting, all the way up to fuel injection nozzles for rockets and jet engines, fan and turbine blades, as well as large metal structures derived from sacrificial investment casting patterns,” explains Patrick Dunne, VP, advanced application development, 3D Systems, Inc.
Applications printed continue to evolve. “Until recently, the industry mostly focused on prototyping during design processes, but recently moved on to printing large parts, jigs, fixtures, and molds. In the just the last few years, end use cabin parts are a realistic concept for retrofitting and spare parts. In the coming years, this trend will accelerate as even more engineering grade, European Aviation Safety Agency (EASA) certified materials become available and printing technologies more cost efficient,” shares Black.
Myerberg agrees that going forward, customized one-off parts for aircrafts will be popular. In the private airspace sector 3D printing is already used for interior features like air conditioning ducts and even custom handles.
“We’ll see manufacturers taking greater advantage of the freedom to design more elegant parts that are lighter weight and consolidate assemblies in ways that are only possible with AM. Completion centers will create truly customized one-off parts for an aircraft interior,” adds Sevcik.
British Airways recently published its top ten predictions for how 3D printing could be used by airlines. This includes cutlery, products for amenity kits, tray tables, aircraft windows, in-flight entertainment screens, seats, baggage containers, circuit boards for electrical components, flight deck switches, and aircraft shells.
Structural components to aircraft are what Killian foresees as being affected in the future, especially due to the industry’s priority of less weight. “Typically, structural parts are too big for 3D writing processes, but the industry is finding a lot of applications with 3D printing for both aluminum and titanium in structural areas where they can design a part with less weight,” he continues.
Aluminum, titanium, and even ceramic are newer materials changing 3D printing processes. “Ceramic printing is beginning to emerge in this sector. One of the first ceramic applications for aerospace was the printing of cores used in investment casting of turbine blades. Turbine designs are reaching levels of complexity that are not possible to achieve with traditional injection molding and machining processes, so AM is key to a path forward on design improvements for turbine efficiency,” adds Allan.
“Forward thinking companies are printing aircraft parts that are typically expensive to purchase and slow to be delivered. Because the technology can be implemented on site, maintenance professionals and engineers do not need to wait for deliveries, creating a digital warehouse anywhere in the world,” states Heiden.
It is the fourth industrial revolution, says Myerberg, or as he refers to it “massive distribution of manufacturing.” Aerospace/aeronautic companies are able to ship digital files to any location and can print on site.
According to ISO, there are seven types of 3D printers, material extrusion, vat photopolymerization, material jetting, binder jetting, powder bed fusion, direct energy deposition (DED), and sheet lamination.
“All of these technologies can be used for aerospace. Some of these technologies also lend themselves well to tooling, fixtures, and jigs, which make manufacturing efficient, faster, or less costly,” says Jonathan Schroeder, president, 3D Platform.
Two prevalent processes used in aerospace/aeronautics are selective laser melting (SLM)—also referred to as direct metal laser sintering (DMLS)—and direct metal printing (DMP), both of which are considered powder bed fusion technologies and involve metal-based filaments.
“DMLS or SLM was the first technology to be adapted by the aeronautics and aerospace industries about 20 years ago. About 15 to 20 years were spent qualifying these processes so they can be used in the ways we now know them to be used today,” explains Myerberg.
Since SLM was the first metal AM technology available in an industry mature state, it became the starting point for AM in aerospace, agrees Röhrich. “After several years of testing and qualifying we are seeing the first parts flying.”
The metal powder bed fusion process is one of the best combinations of precision, repeatability between builds, and ability to print commonly used aerospace/aeronautical materials, for example Inconel 625 and 718 nickel- and Ti-6AI-4V titanium-based alloys, according to Lang.
“SLM and DMP make the most sense for this industry given the part strength and lack of support materials powder-based printing can provide. It’s harder for other printing methods to achieve those results with metals, but I see this changing in the near future as alternate methods catch up and exceed the capabilities of powder-based machines,” adds Baehrend.
DED is an AM process that also uses metal powders or wires. “It relies on a heat source like a laser to deposit material form or wire form onto flat surfaces or existing parts. Because of this, it forms parts additively and enhances or repairs existing components. The process doesn’t have the fine resolution as SLM and DMP, but it does have much higher productivity and can scale up to build larger parts easily,” explains Lang.
Those Alternate Methods
Besides SLM and DMP, other 3D printing processes are used in aerospace/aeronautics. Material types beyond metal are applicable in this segment, which introduces the industry to these other processes.
Material extrusion technologies, which enable printing with thermoplastics and polymers, are one option. Two processes part of this family are fused filament fabrication (FFF) and fused deposition modeling (FDM).
Heiden explains that FFF is “typically applied in a bottom up fashion. Start with simple tools that are not critical, yet immediately add value to do things faster or save costs. This is the type of application that allows even relatively unexperienced people to add significant value. You don’t need extensive material knowledge or design capabilities to be successful and achieve short-term return on investment,” explains Heiden.
“FFF 3D printing technology is on the verge to become one of the most performing and used 3D printing technologies. It allows companies to replace light alloys like aluminum with super polymers, guaranteeing a reduction of weight, fuel consumption, and carbon dioxide emissions,” says Guicciardini.
She cites applicable FFF filaments like polyetheretherketone (PEEK) and polyetherimide (PEI), which are thermoplastics, as suited for the aerospace sector because of their “extraordinary properties in terms of mechanical, thermal, and chemical resistance.” PEEK offers resistance to aggressive chemical agents like Kerosene, making it ideal for components used close to engines such as brackets, clips, harnesses, and plates. PEI is used for non-visible components found in an aircraft’s cabin like ducts or brackets.
“Though FFF AM is frequently used for tooling and other applicable applications, a lack of EASA-certified, flame retardant materials has prevented the possible end use applications of thermoplastic extrusion 3D printing technology in aerospace. However, as newly available flame retardant materials pass the EASA standards it’s clear to see that FFF applications in aerospace will skyrocket as the technology is applied,” agrees Black.
FDM is popularly used in prototyping, specifically prototyping certain parts before they are final printed in metal, according to Baehrend. “The speed, strength, and cost efficiency of FDM tend to be reasons why. I believe it can be utilized further in the near future as the technology continues to evolve,” he admits.
Sevcik notes that aerospace companies also use FDM for tooling. Stratasys’ customers in this sector use acrylonitrile styrene acrylate or ASA—a thermoplastic, polycarbonate (PC), and carbon fiber-filled nylon for a range of tooling applications like basic jigs, fixtures, and templates. PC is also used to produce compression blocks for sheet metal forming and PEI is used for high-temperature lay-up molds for composite forming.
A form of vat photopolymerization, digital light processing (DLP), works with ceramic materials used in aerospace/aeronautics. “The parts are produced out of a high solids loading slurry, and the process yields high smoothness surface finish. This is critical to ensure high strength and good performance, as ceramics are most sensitive to surface defects. The surface finish achieved in printing then carries through the rest of the manufacturing process as the parts undergo binder burnout and sintering. Post processing after sintering is not needed, except for possible polishing steps,” explains Allan.
Gain a Better Understanding
3D printing maintains a prominent place in manufacturing of not only prototypes and tooling, but final parts in aerospace/aeronautics. This will only grow as well-informed companies recognize the possibilities of the technology. “The people on the front line of problem solving in aerospace are gaining a better understanding of AM’s tooling capabilities. Combined with these technologies continuing to advance and evolve, this yields expansion of adoption,” shares Dunne.
SLM or DMLS, DMP, and DED are proven 3D printing processes that work with metal powders and wires. Expanding into the field are FFF, FDM, and DLP. FFF and FDM are ideal for thermoplastic and polymer filaments and these materials’ properties continue to gain in terms of mechanical, thermal, and chemical resistance. The same can be said of ceramic printing using DLP. Specifically, this 3D printing process enables levels of complexity not possible with alternative manufacturing methods.
3D printing’s mark on the aerospace/aeronautic sector is formidable and as seen from these growing technologies, this will continue into the future.
Apr2020, Industrial Print Magazine