by Melissa Donovan
The aerospace industry is a huge proponent of three-dimensional (3D) printing, primarily because the technology creates lighter, more durable, and less expensive components. It’s used for prototyping, tooling, and flight parts.
Metal is particularly useful in the aerospace segment, which means additive manufacturing (AM) using different types of metal is especially advantageous.
Above: Prima Additive’s Print Genius 400 machine platform can reach a working area of 430x430x1000 mm in its XL version, which is ideal for the production of components for aerospace.
Earliest and Largest
The aerospace industry was one of the earliest adopters of 3D metal printing and remains a prevalent user of the technology today.
“Metal AM technologies present great opportunities in terms of design optimization and the possibility of increasing component performance. However, historically they have been quite expensive. For this reason, one of the main sectors since the beginning to approach AM was aerospace which, given the high added value of its components, could afford a more expensive process compared to traditional technologies in exchange for a significant increase in the final performance of the aircraft,” explains Daniele Grosso, marketing manager, Prima Additive.
Dr. Jason Riley, COO, Fabrisonic, says the aerospace industry was one of Fabrisonic’s earliest adopters due to its challenging requirements and sensitivity to weight. This continues today thanks to benefits like “the integration of multiple engineering functions into a single part, reducing weight, enhancing performance, and manufacturing with materials difficult or impossible to machine or cast.”
With the cost of acquiring metals expensive—especially high-performance and high-value metals—it makes sense that this market segment favors AM. “The benefits that AM offers are to reduce the amount of metal required to make a part, and then reduce the amount of machining to complete the part. So, for metals that have a high cost to acquire, and a high cost to machine, this business case is favored,” explains John O’Hara, global sales manager, Sciaky, Inc.
Also, “aerospace is an industry that frequently struggles with long lead times and complicated supply chains. 3D printing is a great tool to deal with those challenges,” notes Mike Shepard, VP, aerospace and defense, 3D Systems.
Brad Kreger, CEO, Velo3D, states that the aerospace industry is broad and as such the Velo3D team “generally thinks of the industry in several buckets, including space—both new space and conventional space companies; defense—munitions, space, and aviation; and commercial aviation. The value pillars across those three categories vary as does their adoption.”
Kreger says aerospace is one of the largest users of the technology. “The value metal AM provides to the new space industry is the ability to produce extremely complicated designs that would otherwise be impossible to produce. That includes net-new designs as well as part consolidation, which can provide performance and durability improvements while reducing weight.”
The defense industry continues to grow its adoption of AM, according to Kreger, driven by ongoing global conflicts where the U.S. and other nations have had to greatly increase production of munitions.
Finally, the commercial aviation industry—while it has explored AM—is still struggling to execute it at a higher rate of adoption. “It is our belief that the level of qualification needed for commercial aviation combined with inconsistency and lack of repeatability in legacy AM systems is primarily responsible for holding back this sector,” states Kreger.
The aerospace industry turns to AM to meet challenges head on. “Metal 3D printing is a good fit for the aerospace industry because it enables weight reduction, creation of complex geometries, as well as quick iterations for prototyping and testing new designs. It also helps offer reduced lead times for part production,” summarizes Miguel Verdejo, product manager – AM, TRUMPF Inc.
Checking the Boxes
Aerospace has a special set of requirements when it comes to 3D metal printing.
Members of the aerospace industry constantly look for ways to improve fuel efficiency and overall performance, this is often achieved by reducing weight though special materials and complex shapes—something 3D printing excels in, points out Dr. Riley.
Scalability is a necessity. “A key requirement within the aerospace industry—as well as most other industries—is the ability to achieve reproducible outcomes across different printers of the same model without extensive, ongoing qualification. This challenge has led to a stall in the adoption of AM technology. As a part design is validated and enters its scale-up production phase, companies must be able to add additional printers without regressing to the qualification stage. That scalability is critical when it comes to producing parts in any significant volume,” admits Kreger.
“The metal 3D printing process needs to be repeatable, and the machines must have process monitoring capabilities to ensure that repeatability, as well as identify issues during the printing process that might adversely affect the quality of the finished part,” agrees Verdejo.
Simplicity is key. “A significant interest on the part of aerospace companies is the simplification of parts using 3D printing. When previously, parts were made using multiple manufacturing techniques and numerous components, 3D printing enables multi-component parts to be made in a single process. This reduces bill of material items, manufacturing and assembly time, and increases performance,” shares Dr. Riley.
Specific standards and certifications must be met. “There is an important issue regarding the certification of the components, in which we as manufacturers of industrial systems work together with customers to support them in optimizing the process, even if the burden of component certification continues to be on the end user rather than the machine manufacturer,” explains Grosso.
Requirements are always changing, but Shepard says some standards are just standards, and necessary to approve a 3D printed part or tool. “Requirements are constantly maturing but have mostly gelled. Most aerospace OEMs use some combination of internal and industry-wide specifications. These cover a lot of ground and often specify critical quality parameters for feedstock, processing parameters, post processing, etc., as well as mechanical property requirements.”
“Safety is the most important consideration when it comes to metal 3D printing in the aerospace industry, especially for loadbearing components, process qualification, and fatigue resistance. The industry ensures safety through certification, which can be expensive and time consuming if all inspections happen after manufacturing. However, with in-situ process monitoring (ISPM), 3D printers can monitor the printing process for defects during the build time,” shares Erik de Zeeuw, market manager for aerospace, Materialise.
Above all, O’Hara is adamant that “AM must make good business sense. This means it must reasonably save money, or solve another problem that traditional processes cannot solve.”
Aerospace Trends
3D metal printing is used for prototyping, tooling, and flight parts in aerospace.
“Aerospace companies focus on structural components, jet engine components, heat exchangers, and combustion components such as turbines, propellers, and rocket thrusters,” shares Verdejo.
More specifically, returning to the three main segments in aerospace according to Velo3D, “in space, many of the parts being produced include combustion chambers, nozzles, turbo pumps, heat exchangers, and fuel tanks. The trend we see is that any opportunity to improve performance and reduce weight are key to making the case for using AM to produce parts,” shares Kreger.
O’Hara believes parts used for production will grow. “Prototypes are a convenient and essential part of AM, but if anyone is going to make money in AM we need to get into production.”
On the software side of things, de Zeeuw believes there is an increased focus on process control in metal 3D printing for aerospace “to ensure the quality of each individual part using this manufacturing method. Due to the large size of processing data and the complexity of related analytics, the digital thread of the data showing products’ performance and use throughout their lifecycles, is key for the aerospace industry.”
“Additionally, sensors in 3D printers that enable ISPM are increasingly helpful in replacing expensive and time-consuming post-manufacturing inspections with monitoring during the build process. These post-processing inspections are still required in traditional manufacturing methods,” continues de Zeeuw.
The most notable trend is increased adoption. “3D printing is a newish, powerful tool in the aerospace manufacturing toolkit. As various organizations understand the capabilities and limitations of the processes, they are employing 3D printing more broadly, more effectively, and with lower risk,” adds Shepard.
Popular Metals
Aluminum, nickel, titanium, and copper are well regarded when it comes to 3D printing aerospace applications.
Velo3D experienced the most interest of late in Aheadd CP1, an aluminum alloy developed by Constellium specifically for AM. “Compared to other aluminum alloys, like those in the aluminum–magnesium-silicon family, Aheadd CP1 greatly reduces the post processing required after printing parts—a one-step, four hour heat treatment process compared to a much longer, multi-step process that includes heat treatment, quenching, and age hardening,” explains Kreger.
“Aluminum offers strength, thermal properties, low weight, and flexible post processing. Scallmaloy is the highest strength aluminum alloy available in 3D printing and has density-specific properties. This makes it ideal for use in highly loaded and safety critical parts,” explains de Zeeuw.
Most of Fabrisonic’s work involves aerospace aluminum alloys such as 6061, 70xx, and 20xx. “These materials have been an aerospace staple for over a century due to their excellent strength-to-weight ratio,” says Dr. Riley.
Nickel, titanium, and refractory metal alloys are common. “These are high-value metals, so they support a great business case,” explains O’Hara.
More specifically, Verdejo cites titanium Ti-6AI-4V and nickel-based superalloys Inconel 625 and Inconel 718 as some of the more popular metals. Refractory metal alloys include niobium (C103) for high-temperature applications.
“High strength-to-weight ratio, high corrosion resistance, and high temperature resistance are some of the reasons that these alloys are used,” continues Verdejo.
While Inconel is historically one of the most used materials for aerospace applications, Grosso says copper alloys and pure copper are emerging as components in this sector. “One of the possibilities offered by direct energy deposition (DED) solutions is also that of creating multi-material components, building, for example, the inside of the part in copper and the outside in Inconel to optimize the functionality and thermal conductivity of the finished component.”
“Copper alloy combines electrical and thermal conductivity with strong mechanical properties. It is typically used in rocket engine parts, heat exchangers, and induction coils,” explains de Zeeuw.
“Moving forward, metal 3D printing, especially laser powder bed fusion (LPBF), has really opened opportunities for exciting new alloys. New alloys have always struggled to win widespread adoption, but I think some of the new formulations have compelling properties. Many of these alloys feature clever ways to control nucleation and grain growth during solidification and heat treatment and/or use computational alloy development tools to discover new, useful alloy chemistries. It will be exciting to see how these new alloys mature commercially,” explains Shepard.
Popular Methods
A host of 3D metal printing processes are used in the aerospace industry. These include DED, direct metal laser sintering (DMLS), fused filament fabrication (FFF), LPBF, selective laser melting (SLM), and ultrasonic additive manufacturing (UAM).
LPBF technology is of value here “because of its ability to print highly complicated parts with excellent resolution. In addition, it can yield densities that are on par and greater than casting, making it easier to position as a casting alternative,” states Kreger.
For metals, LPBF is the most common, according to Shepard. “The foundations of the process are consistent, but each vendor performs the operations in slightly different ways. For example, 3D Systems’ DMP or direct metal printing process is our version of LPBF, where we perform the operation in a very low oxygen—and other interstitial—environment. Our customers have found this makes a real difference in surface finish, mechanical properties, and the ability to reuse (expensive) metal powder till the lot is exhausted.”
SLM and DMLS, being in use the longest, are among the more popular printing processes used today, shares O’Hara. But he admits that this will not always be the case and foresees DED growing in popularity because of its wider range of applications.
Grosso sees DED technology playing an increasingly important role, “ore components, especially in the space sector, are made with this technology, which is proving to be very competitive when it comes to making large parts with simple geometries.”
“DED for metals is used, though less extensively, and is winning some really interesting niche applications for large metallic structures with rotational symmetry—rocket nozzles, rocket bodies, etc,” admits Shepard.
FFF is also popular in aerospace. “FFF for quick prototyping as well as low-volume production. The technology provides quick lead time for both prototyping and production applications. FFF enables production of complex parts that cannot be made with traditional processes,” says Verdejo.
“FFF is used in selected flying applications where polymers are acceptable. It is a good technology for jigs, tools, and fixtures. It is being complemented now by pellet extrusion, which is faster and more economical, especially for large structures, because of the low cost of injection molding pellet materials compared to high-quality filament,” explains Shepard.
Another process is Fabrisonic’s UAM process, which uses rolled metal foil as feedstock. It can be purchased off the shelf as traditional aerospace-grade aluminum meeting AMS standards.
“Each 3D printing method provides its own unique benefits, to which engineers design parts. We are currently at a time when there is no dominant 3D printing technology. Aerospace companies are using numerous 3D printing methods as they conduct R&D, design advanced components, and innovate,” explains Dr. Riley.
Leading Role
The aerospace sector was an early adopter of 3D printing technology and continues to take the lead today. There is no dominate AM process used, each company relies on their desired technology—DED, DMLS, FFF, LPBF, SLM, or UAM—to manufacture the parts, prototypes, and tools they require.
Oct2024, Industrial Print Magazine