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ADDITIVE MANUFACTURING IN AEROSPACE & DEFENSE INDUSTRIES

Milton D’Silva presents an overview of how additive manufacturing is revolutionising the aerospace & defense sectors.

ADDITIVE MANUFACTURING IN AEROSPACE & DEFENSE INDUSTRIES
Airbus Helicopters 3D printing centre. Source: Airbus

In the end, it took a walnut-sized component to break the mindsets and design bottleneck in aerospace, a giant leap of faith for GE Aerospace. The component in question is the fuel nozzle designed and 3D printed by GE Additive for the LEAP jet engine in 2015. Previously assembled from 20 parts, this complex nozzle that fits in the adult human palm is now a one-piece marvel of engineering, thanks to 3D printing. Imagine welding 20 different parts to assemble such a complex yet critical component and the stringent checks it must undergo in the process. The 3D-printed nozzle not only weighs 25 percent less than its traditionally manufactured counterpart; but is also five times more durable and 30 percent more cost-efficient. Over 200,000 units have been shipped in the last 8 years and GE Additive – recently renamed as Colibrium Additive combining the two English words ‘collaboration’ and ‘equilibrium’ – is currently manufacturing 1000 units every week. “While we are changing our name, we maintain our unwavering focus on our customers, quality, and reliability. We will continue to lead the additive manufacturing industry from the front and positively disrupt it,” said Alexander Schmitz, CEO, Colibrium Additive, announcing the development in April 2024.

A Disruptive Technology
Described as one of the most disruptive technologies of the digital era, the history of additive manufacturing actually dates back to the 1980s when digital just meant an alternative to analogue. It began with Japanese scientist Dr Hideo Kodama of the Nagoya Municipal Industrial Research Institute, while working on a more practical way to develop a rapid prototyping system, first thought of and documented a layer-by-layer approach for manufacturing, similar to what modern 3D printing has evolved today. Though Dr Kodama did not file any patent, he is credited as the earliest proponent of additive manufacturing, the layer-by-layer approach to building a component, instead of the prevalent method of subtractive manufacturing.

Later in early 1984, Frenchmen Alain Le Méhauté and Olivier de Witte then working with the French General Electric Company (now Alcatel), who were working with liquid monomers, took the idea to Jean Claude André at the French National Center for Scientific Research (CNRS), but for some reason they could no file the patent. Even as several other researchers were working on the idea, it was American Charles Hull, who invented stereolithography (SLA), a process that solidifies thin layers of ultraviolet (UV) light-sensitive liquid polymer using a UV laser. Chuck Hull, as he is popularly known, was working with a furniture manufacturer and looking for an easy way to make custom parts for which there were no suppliers. The patent for his SLA technology was granted in 1986, and the same year he started his own company, 3D Systems in California. The first commercial 3D printer, the SLA-1, was released in 1988, and Chuck Hull is widely recognised as the father of additive manufacturing. Stereolithography or SLA, which uses a laser to cure and solidify layers of photopolymer resin, is widely used for prototyping, and also has applications in dental and jewellery.


ADDITIVE MANUFACTURING IN AEROSPACE & DEFENSE INDUSTRIES
The fuel nozzle manufactured by GE for the LEAP jet engine. Source: GE Additive

With efforts continuing to fine-tune, refine and further develop new materials and methods, other processes were developed subsequently which may be summarised as follows:
  • Digital Light Processing (DLP): A process similar to SLA, but one that uses a digital light projector to flash a single image of each layer all at once. DLP uses photopolymer resins for building components, and like SLA, has applications in prototyping, dental and jewellery fields.
  • Fused Deposition Modeling (FDM): This process melts and extrudes a thermoplastic filament through a heated nozzle, layer by layer, with thermoplastic materials like ABS, PLA, PETG, and composites. Applications are in areas of prototyping, functional parts and hobbyist projects.
  • Selective Laser Sintering (SLS): This is a process that uses a laser to sinter powdered material, binding it together to create a solid structure. It makes use of materials like certain plastics, ceramics, and metals. Applications are for making functional prototypes, end-use parts, and components with complex geometries.
  • Multi Jet Fusion (MJF): A process that uses an inkjet array to apply fusing agents to a powder bed, which are then fused by heating elements, MJF makes use of materials like nylon and other polymers. Applications are for making functional parts, small to medium production runs, and detailed objects.
  • Direct Metal Laser Sintering (DMLS)/Selective Laser Melting (SLM): These are processes that make use of lasers to melt and fuse metallic powder, made from metals like titanium, aluminium, and stainless steel. Applications are in aerospace, medical implants, and high-performance engineering components.
  • Electron Beam Melting (EBM): This process uses an electron beam to melt metallic powder layer by layer, and the materials used are metals like titanium and cobalt-chrome. Applications are in aerospace, medical implants, and industrial parts.
  • Binder Jetting: This process deposits a liquid binding agent onto a powder bed, layer by layer, to bond the material. The materials used in binder jetting are metals, sand, ceramics, and polymers. Applications are for casting moulds, metal parts, and full-color prototypes.
  • Material Jetting: A process that deposits droplets of photopolymer or other material that are then cured or hardened, material jetting uses materials like photopolymers and other polymers. Applications are for making full-colour models, prototypes, and parts with complex geometries.
  • Laminated Object Manufacturing (LOM): In this process, layers of material are bonded and then cut into shape by laser or another cutting device. Materials used are paper, plastic, or metal laminates, with applications in prototypes, casting patterns, and aesthetic models.
Together, these are the various technologies – the list is neither complete nor comprehensive – but in general, cater to various industries, including aerospace, automotive, healthcare, consumer goods, and more, providing a range of solutions from rapid prototyping to end-use part production. What began in the early 1980s as an experimental technology for rapid prototyping has today blossomed into a sophisticated technology for making complex products with intricate designs, building them layer by layer, the materials ranging from a variety of polymers to various metals and compounds. While 3D printing and additive manufacturing (some also call it additive layer manufacturing or ALM) both refer to the same process, today the term 3D printing is associated more with consumers and hobbyists while additive manufacturing has acquired professional credentials for industrial and commercial applications!

Relevance to Aerospace & Defense
Additive manufacturing today has pervaded every industry segment with a wide acceptance level aided by the democratisation of the ecosystem that is available not just to industrial behemoths like GE, but also to hobbyists holed up in small cubicles yet working on realising their dream projects. From high school students to academies of higher learning and advanced research institutes, everyone has access to the technology at affordable price points. However, it is the aerospace and defense sectors where additive manufacturing is of particular relevance owing to the very nature of these industries, which are at the forefront of technological innovation, always in the quest of practical solutions to some very intractable problems that stand in the way of squeezing in that extra performance, pushing the efficiency envelope a bit further, and above all shrinking the all-important timelines.


ADDITIVE MANUFACTURING IN AEROSPACE & DEFENSE INDUSTRIES
The first ever 3D printer sent to the International Space Station in 2014. Source: NASA

The reasons are not far to seek. The aerospace industry, according to the Britannica definition, is an assemblage of manufacturing concerns that deal with vehicular flight within and beyond Earth’s atmosphere. The term aerospace, derived from the words aeronautics and spaceflight, represents unpowered gliders and sailplanes, uncrewed aerial vehicles (UAVs), lighter-than-air craft, heavier-than-air craft including military aircraft, missiles, space launch vehicles, and spacecraft, which has an overlap with the defense sector. The latter in turn also shares many of the issues that are of importance in aerospace like material strength, lightweighting – in other words, the need for lightweight materials of high strength. The defense sector, in addition, has operational needs to tailor mission-critical components at short notice where there is no supplier base, without compromising operational preparedness while reducing costs associated with mass production.

Among the major benefits of additive manufacturing is weight reduction of aircraft components which leads to less fuel consumption. This also contributes to reducing CO2 emissions during operations. Other advantages include increase in resource efficiency in the manufacturing process and high flexibility. From the defense applications perspective, delocalised production is a significant advantage bringing production closer to the point of use, saving time. The fact that this is also highly suitable for small batch sizes and customised parts is another major benefit.

Applications Success Stories
A July 2023 study of global aerospace and defense additive manufacturing market published by Virtue Market Research states that the market was valued at USD 4.46 billion and is projected to reach a market size of USD 18.56 bn by the end of 2030.

Buoyed up by the early success with the jet nozzle, Colibrium Additive (formerly GE Additive) has ramped up capacity and extended the metal additive manufacturing activities to several other segments within aerospace and defense. This includes comprehensive one-stop services that include metal 3D printers (Laser, Electro Beam and Binder Jet), a wide portfolio of powders including standard and custom powders and those for specialised applications comprising titanium, aluminium and nickel alloys. The LEAP jet nozzle has been followed by a succession of products like the GE90 T25 sensor housing that became the first FAA-approved 3D printed part; jet wing brackets for Airbus A350 XWB turbofan engines; aluminium heat exchanger for the GE9X engine; low-pressure turbine blades; and titanium door hinges, among many other parts. Colibrium Additive has also helped Staco, a South Korean additive manufacturing company, build parts for South Korea’s first private rocket launch. Earlier this year, GE Aerospace announced an investment of 650 million USD into its manufacturing facilities of which more than 150 million USD was allocated to facilities running additive manufacturing equipment.


ADDITIVE MANUFACTURING IN AEROSPACE & DEFENSE INDUSTRIES
Thermal Chuck developed and produced by Staco through Colibrium Additive's M2 Series 5. Source: Colibrium Additive

At the Airbus main helicopter production site at Donauwörth in Germany, the company has opened a new 3D printing centre to expand in-house capacity for additive manufacturing, comprising three machines for components made of titanium, four for plastic parts and a machine that can produce components made of aluminium. The facility can be used for serial production as well as for components for prototypes such as the electrically powered CityAirbus NextGen and the experimental high-speed helicopter, Racer. According to a company press release, since 2017, Airbus Helicopters has mass-produced more than 9,400 locking shafts for the doors of the Airbus A350, using the additive process as part of the Donauwörth-based airplane door business. Eleven tonnes of titanium powder have been used in Donauwörth for printing the locking shafts.

Seattle (Washington) based Boeing opened its Boeing Additive Manufacturing plant (BAM) just at the beginning of the COVID-19 pandemic (the plant officially opened in 2022, but the company says it has been additive manufacturing in various forms for over 30 years. While earlier Boeing started with tooling, followed by polymer, it has now turned to metal, like its peers, to reduce costs and production time. At present, Boeing is reportedly using AM parts for doors on 777s, internal parts on the spacecraft Starliner and winglets on 737s, among other things. This 787 manifold used to be three separate pieces assembled together, which is now produced as a single part. In an interview published in its in-house Innovation Quarterly (IQ) a while ago, Dr Melissa Orme, Vice President, Boeing Additive Manufacturing mentioned that additive manufacturing is changing the way Boeing designs and builds aerospace products, allowing the company to use less raw materials, create less waste and improve fuel efficiency. “Significantly less material is required to create a part with additive methods, reducing the carbon footprint at the front end. As for the end product, AM enables highly innovative designs that add functionality, reduce weight and volume, and consolidate many parts into one, further adding to Boeing’s sustainability goals,” she said.

In early 2024, Boeing also awarded Space Foundation Discovery Center, a nonprofit organisation founded in 1983, a grant to fund a new Additive Manufacturing Space Lab. Devoted to 3D design, printing, and other additive manufacturing and fabrication methods, the Boeing Additive Manufacturing Space Lab will be a new immersive education lab serving students, teachers and industry across the globe.

While on the topic of space the first ever 3D printer was sent to the International Space Station in September 2014 aboard the SpaceX CRS-4, an unmanned craft. Manufactured by Made In Space, Inc., with NASA, this first zero gravity plastic 3D printer signaled new possibilities for manufacturing objects in space. According to the NASA news portal, on December 11, 2014, the printer's first functional application was announced: a buckle developed by NASA astronaut Yvonne Cagle. This buckle is part of exercise equipment to assist with the reduction of muscle loss in zero gravity environments. Several other plastic 3D printers have since been sent to the ISS and many parts manufactured. However it was only in January 2024 that the world’s first metal 3D printer was sent to the ISS. Developed by Airbus and Space SAS for the European Space Agency (ESA), the metal 3D printer flew to the ISS aboard the Cygnus NG-20 mission, which was launched aboard a SpaceX Falcon 9 rocket. Apart from manufacturing replacement parts, a long term goal is to try and repurpose old satellites by building new parts to help create a circular economy in space.

Rheinmetall, a leading, globally active, integrated technology group that develops and sells components, systems and services for the security (defense equipment) and civil industries, also uses additive manufacturing and had installed the first SLM machine into operation in 2012. Later, the group launched a startup, Solidteq, in 2017 for the next generation of intelligent industrial production for in-house requirement and to also offer its expertise to third-party customers, in particular from the automotive and mechanical engineering sectors. Solidteq has since commissioned more SLM units at its facility in Neuss, Germany, in order to address the rising demand for its Additive Manufacturing services. Rheinmetall has also used the services of toolcraft, another German company, which specialises in additive manufacturing, to produce components for a turret-independent secondary weapon system (TSWA) by means of additive manufacturing. Rheinmetall Defence Australia (RDA) has used locally printed 3D products in its Lynx armoured fighting vehicle, sourced from Formero (formerly GoProto ANZ), Australia's largest 3D Printing & Traditional manufacturing services bureau.

In the USA, Lockheed Martin, a leading global security and aerospace company, became the first organisation to be certified to UL 3400, a set of safety guidelines that address the various hazards associated with additive manufacturing facilities. Granted in 2018, the certification was issued to its Additive Design and Manufacturing Center (ADMC) in Sunnyvale, California. The ADMC has manufactured several components including an aluminium box for avionic circuits for a high-frequency communications satellite, and a dome for high-pressure fuel tanks used in spacecraft. Lockheed Martin has recently teamed up with Sintavia, which claims to be the world's first all-digital aerospace component manufacturer, to advance metal additive manufacturing and demonstrate its commitment to the White House AM Forward initiative for expanding use of additive manufacturing and creating resilient supply chains. Announced in May 2022, the new collaboration will explore additional AM technology areas, including laser powder bed fusion, electron beam-directed energy deposition and friction stir AM.


ADDITIVE MANUFACTURING IN AEROSPACE & DEFENSE INDUSTRIES
Component developed by Sintavia from niobium alloy for space applications. Source: Business Wire

The AM Forward is a public, voluntary agreement announced by five large US manufacturers – General Electric Aviation, Honeywell, Siemens Energy, Raytheon Technologies, and Lockheed Martin, to help their suppliers adopt additive manufacturing. Through AM Forward, OEMs will work directly with their US-based suppliers to demonstrate clear demand for additively produced parts. These companies have also committed to providing technical assistance and worker training to suppliers, and to work together to develop standards for additive manufacturing. US President Joe Biden stated that his administration will support this effort with a variety of current and proposed Federal initiatives.

In India, the Additive Manufacturing Society of India has played a vital role as an expert committee member in framing the National Strategy for Additive Manufacturing along with the Ministry of Electronics and Information Technology (MeitY), Government of India. Among the Society’s goals is networking with global 3D printing organisations to achieve Make In India and position India as a hub for 3D Printing development and implementation. The MeitY has framed the ‘National Strategy for Additive Manufacturing” in February 2022, which aims to create a more conducive environment for the development and deployment of AM technologies, while encouraging its adoption by local manufacturers. In April 2024, Indo-MIM, the world’s leading Metal Injection Moulding (MIM) company, installed two HP metal 3D printers – the advanced Metal Jet S1003D Printing Solution – at its Doddaballapur plant near Bengaluru in Karnataka. This makes Indo-MIM the first company in India to set up a large-scale production facility for high-precision, 3D-printed metal parts for automobile, aerospace, defense, consumer electronics, medical equipment and lifestyle segments. At present AM technologies are widely adopted in the automobile industry, and in medical appliances and dental treatment. A notable success was achieved recently when a rocket featuring the world’s first 3D-printed, single-piece rocket engine, Agnilet, blasted off in late May 2024. The rocket engine was fabricated by Agnikul Cosmos, a space tech start-up mentored at IIT-Madras in Chennai, for its Agnibaan SorTeD (SubOrbital Technological Demonstrator) single-stage launch vehicle. The Agnilet engine, an entirely 3D-printed, single-piece, 6 kN semi-cryogenic engine, is a technology patented by Agnikul Cosmos.


ADDITIVE MANUFACTURING IN AEROSPACE & DEFENSE INDUSTRIES
The metallic 3D printed rocket engine developed by Agnikul. Source: Agnikul Cosmos

These examples, coupled with government policy initiatives, make it amply clear that the revolutionary potential of additive manufacturing is gradually being discovered and adopted by industry. A large passenger aircraft is made of millions of individual parts if one includes all the sub-assemblies and fasteners that go into its making and assembly. An additively manufactured component, as seen from the examples, often combines many individual parts that are bolted or welded together to make a one-piece assembly, saving weight while offering added strength, with the added benefit of cost savings, also reducing use of metals and materials in the process. The revolution has just begun.

The Pros and Cons
When it comes to the advantages of additive manufacturing, these are well documented and also obvious from the preceding paragraphs. But here, once again, a brief listing is presented for easy reference:
  • Material Innovation: New materials, such as high-performance polymers, metals, and composites, are being developed specifically for AM. These materials offer superior strength-to-weight ratios and durability.
  • Precision and Complexity: AM enables the production of intricate designs that were previously impossible or cost-prohibitive with traditional manufacturing methods. This capability is crucial for aerospace and defense applications, where precision is paramount.
  • On-Demand Production: The ability to produce parts on demand reduces the need for large inventories, leading to cost savings and improved supply chain efficiency.

Benefits in Aerospace

  • Weight Reduction: Lighter components lead to fuel savings and increased payload capacity. The best example is the jet nozzle for GE Aviation's LEAP engine cited right at the beginning.
  • Cost Efficiency: By reducing material waste and simplifying the manufacturing process, AM can significantly lower production costs. This is particularly beneficial for low-volume, high-value aerospace parts
  • Customisation: AM allows for the customisation of parts to meet specific requirements, improving overall aircraft performance and maintenance.
  • Rapid Prototyping: AM accelerates the development and testing of new defense technologies, enabling faster response to emerging threats.
  • Field Manufacturing: The potential for on-site production of parts and equipment in remote or hostile environments enhances operational readiness and reduces logistical challenges.
  • Enhanced Design Capabilities: The freedom to design more complex and efficient structures can lead to improved weapon systems, protective gear, and other defense applications.
However, there are some challenges in wide-scale adoption of additive manufacturing that still need to be overcome. These include:
  • Certification and Standardisation: Ensuring consistent quality and performance of AM parts is critical. There is the ever-important need to first establish and then validate protocols to ensure the integrity of components produced by AM, to ensure they meet or exceed the stringent requirements as in the case of conventionally manufactured products. The development of industry standards and rigorous testing protocols is an ongoing process.
  • Quality Control: This is again a critical requirement and calls for stringent monitoring and parts verification in order to maintain the highest safety and performance standards. Early detection of defects and variations in material properties enable rapid corrective actions.
  • Scalability: As a relatively new technology that started by producing one-off components, scalability is important. This is especially true in case of metal parts manufactured by AM for serial production even as the majority of parts and components are still manufactured by conventional processes.
  • Intellectual Property and Security: In the digital era, protecting sensitive designs and preventing unauthorised reproduction of critical components is a major concern. Solutions include digital rights management and secure data transmission.
  • Addressing the Skill Gap: The adoption of AM requires specialised knowledge and training. The industry has taken the lead by engaging with the student fraternity and further investment in education and workforce development is essential to fully realise the potential of this technology.
Conclusion
Additive manufacturing is poised to revolutionise the aerospace and defense industries. Its ability to produce high-quality, lightweight, and customised components offers significant advantages. While challenges remain, ongoing advancements and the integration of complementary technologies promise a future where AM plays a central role in shaping the next generation of aerospace and defense solutions. Going forward, with the maturing of the digital ecosystem, the combination of artificial intelligence and Internet of Things can optimise manufacturing processes, predictive maintenance, and supply chain management in the emerging industrial metaverse, with digital twin playing an important role. As the world moves towards sustainability and a circular economy, additive manufacturing will become even more important to every industry segment and not just aerospace and defense.

References
1. https://markforged.com/resources/blog/additive-manufacturing-history
2. https://www.colibriumadditive.com/news/metal-3d-printing-now-were-shooting-it-space
3. https://www.rheinmetall.com/en/media/news-watch/news/2023/june/2023-06-28-mobile-smart-factory
4. https://news.lockheedmartin.com/2022-12-07-Lockheed-Martin-Sintavia-Team-Up-Advance-Metal-Additive-Manufacturing
5. https://www.whitehouse.gov/cea/written-materials/2022/05/09/using-additive-manufacturing-to-improve-supply-chain-resilience-and-bolster-small-and-mid-size-firms/

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