Most people have heard of 3D printing, also known as additive manufacturing, but what can it offer to the MRO business? Bernie Baldwin discovers some of the benefits from some leading players.

Whether you refer to it as 3D printing or additive manufacturing (AM), the technology to create a 3D shape, layer by layer, is on the increase, particularly in the aviation industry. And while the two terms refer to the same basic process, it is the latter which is becoming prevalent for items that require greater precision for industrial usage.

The production of aircraft parts generally involves high volume manufacturing, so replacing that requires a strong business case. In recent years, there has been much anxiety about the supply chain for spares, so AM is being seen as a solution to alleviate that concern.

The business case

Melissa Orme, vice president of Boeing Additive Manufacturing, agrees. “The business case for spares is different than for standard parts,” she says. “This is because there is an urgency surrounding the need for spares, especially in the military environment, and often the spares are for older platforms where the tooling or the original supplier may no longer exist.

“The business case to create an expensive tool for a one-off spare part is non-existent. Hence, the ability to additively manufacture the spare part becomes very important, as it provides the option to rapidly manufacture almost any spare part without legacy tools. Additionally, the ability to use AM for low volume one-off tooling for out-of-production parts, to speed up the traditional fabrication process, is also an important business driver,” Orme elaborates.

She continues: “Currently, Boeing is creating a framework to address the rapid manufacture of spare parts through additive manufacturing. Non‑safety-critical parts have already been printed and provided in many instances. For safety-critical parts, we are creating the engineering analysis and testing flow that responds to the urgent need to provide these parts while simultaneously addressing engineering requirements.

“Our first Navair pathfinder for spares on the F/A- 18 will be flight‑tested this year, and this opens the door to subsequent spare parts, which are expected to be qualified in a faster timeframe, leveraging the pathfinder framework.”

EOS is a company specialising in industrial 3D printing technologies, which works with its customers “to innovate and differentiate through expert guidance, technology and services, leveraging its end-to-end additive manufacturing (AM) industry partnerships”. Thomas Friedberger, the company’s key account manager, Aerospace and Defence, explains that the business case is driven by three core factors: producing spares at a lower cost than conventional methods; significantly reducing lead times for production and logistics; and a reduction of physical inventory in the long run.

“Locally printed aircraft spare parts, such as those for cabin interiors, can be produced 30-50 per cent cheaper than the cost of the OEM spare parts, with the added benefit that lead times for production and logistics of usually 12 weeks or more can be shortened to two weeks or even just a few days,” Friedberger says. “Another added value of industrial 3D printing technology is that the design of the parts can be improved to address known weaknesses or to enable part customisation.

“As one of few OEMs, EOS provides high quality technology and materials to deliver parts into regulated industries such as aviation. An incremental benefit of AM is that it enables on-demand manufacturing of required parts in a mixed parts batch, which significantly reduces stock-keeping. Again, this will lead to cost reductions.”

Friedberger adds: “Companies have two options, either source parts from certified service providers – such as our joint venture, the Aviation AM Centre (AAMC) – or build up their own MRO production hub. The capability to offer in-house manufactured spare parts is a strong USP and customer retention tool for aircraft maintenance service providers. In this case, EOS can offer a whole end-toend solution to operate a production hub. And with AAMC, we can help customers comply with regulatory norms.

“Industrial 3D printed spare parts are certified and in service already, so the question is more when AM will fully scale to series production. Geopolitical crises and supply chain resilience are already driving adoption faster than we anticipated.”

Sébastien Aknouche is responsible for material solutions at GKN Aerospace which, while having wide-ranging AM expertise, is particularly strong in using the technology to manufacture aircraft engine components. He too, offers the business case for AM, believing that in the short term, the AM processes with the most important transformation factors are probably driven by the lead time of demand-design-make-deliver.

“It is probably down to five per cent, maybe even less, of the traditional approach for a new demand,” Aknouche remarks. “This is because there are fewer steps in the process than the traditional manufacturing of aircraft parts. Through AM, the lead times for industrialised production are just a fraction of traditional production’s lead times, where any change in demand may take more than two years to meet.

“AM allows for rapid changes in demand and a much more flexible supply situation,” he continues. “This will allow for much smaller inventory and unlock a huge amount of cash currently tied up in inventory. The process also allows for less cost to the customer through higher flexibility of supply and higher security of supply.

“Finally, AM allows us to utilise the already limited global availability of super alloys significantly more efficiently. We may produce two to ten times as many engines with the same amount of metal. This again reduces the amount of waste material.”

Suitable components and processes

While many parts and components can be produced with AM, in these still early stages of its use, there are certain products that are leading candidates to be made this way for spares. “The applications revealing the greatest impact of AM in aerospace are primarily complex, lightweight components such as engine components,” Aknouche contends. “These parts benefit from the design freedom offered by AM, resulting in improved performance, fuel efficiency and reduced environmental impact. Moreover, the ability to consolidate multiple components into a single, intricately designed AM part also contributes to overall weight reduction.”

Boeing’s Orme says that candidate parts for AM production are wideranging. “Any component that is difficult to procure due to obsolescence issues, that can be printed to requirements in one of the qualified material systems and that fits in a qualified printer platform, is an excellent candidate for additive manufacturing,” she states.

This article continues after the below picture…

“That said, simple parts such as brackets, clips and knobs can be readily machined instead if machining capability is available at the point of need. More complex parts are ideal for additive manufacturing.”

For Stephan Keil, managing director of The Aviation AM Centre (AAMC), cabin interior parts are the primary candidates for on-site printing. “Certification of this parts category mainly revolves around flammability testing, which our EOS material PA 2241 FR fulfils for the targeted part sizes that are suitable for printing on EOS systems,” he explains.

“We also see parts from the flight deck and cargo areas, as well as electronic equipment bay are a perfect fit for customers. Recently, we realised that certain aluminium parts can now be additively manufactured using our EOS HT-23 material for applications in the fuel pump systems and others, again bringing weight reduction.”

Like welding, the term additive manufacturing covers a range of processes, many of which suit the creation of certain component types better than others. “Selective laser sintering (SLS), for example, suits cabin interior parts that are visible to the passenger and have high requirements regarding surface quality,” Keil says. “They can be spray-painted or colourdyed in combination with mechanical or chemical surfacing. Currently, SLS parts are the most cost-effective industrial 3D printing solution for aviation.

“Another process, fused deposition modelling (FDM) with high temperature materials, is suitable for large parts that are invisible to the passenger and do not need to be finished with high surface requirements (air ducting, for example),” adds Keil.

The wide range of technologies under the AM banner is also recognised at Boeing. Orme picks out some of the key processes. “For polymer printing of tubes, ducts, covers and similar items there are several options: liquid-based technologies such as stereolithography and digital light processing; powderbased technologies such as selective laser sintering and binder jetting; and filament-based technologies such as fused filament fabrication. The decision of which technology to use resides in the application, material system available, material properties required and surface finish.”

Orme continues: “For metallic components, such as heat exchangers, manifolds, waveguides and other items, the choices include: laser or electron beam powder bed fusion technologies, which are the most prevalent in industry currently; directed energy deposition technologies of either powder or wire source material; wire extrusion; and liquid metal jetting.

“The choice of technology is often governed by the size of the end component,” Orme explains. “Directed energy deposition is useful for larger components with a trade-off of part resolution necessitating more machining than other 3D printing technologies, while powder bed fusion is the choice for components less than approximately 24 inches depending on the printer platform (and newer platforms are extending this size limitation), because the surface finish is better and requires less machining.”

According to Aknouche, GKN Aerospace employs additive fabrication, which involves layerby- layer construction using metal wire or powder fused together with lasers. “Large-scale laser metal deposition with wire (LMD-w) enables the production of complex and lightweight structures,” he comments. “These structures optimise the overall performance of aircraft components, contributing significantly to weight reduction, fuel efficiency and, as noted, the ability to create intricate geometries that were previously challenging with traditional manufacturing methods.”

As the aviation industry moves forward, every new procedure and process will be scrutinised for their improved environmental benefits. The use of AM is no different. “Overall, the AM process fully implemented will bring lower costs to the customer, higher margins for the suppliers, improved utilisation of global resources and much less negative impact on the environment,” Aknouche says. “For example, improved buy-to-fly ratio (the weight ratio between a substrate and a completed part) will enable us to utilise available metal even more efficiently with even less waste.”

Benefits to the environment

EOS’s Friedberger believes that 3D printed products inherently provide added value when it comes to responsible manufacturing. “Lightweight designs help to reduce carbon emissions and functional integration, and product designs solve complex manufacturing challenges while minimising waste,” he remarks.

“Lightweight AM parts incorporated into an aircraft reduce the aircraft’s weight, thereby decreasing not only the fuel consumption and thus the operating costs, but also the CO² footprint of each passenger on board. EOS’s 3D printing technology actively supports making the aviation industry more sustainable.

“Polymer AM enables sustainable spare part production and helps lower manufacturers’ overall carbon footprint. By avoiding the unnecessary creation of excess spare parts, industrial polymer 3D printing also helps streamline the supply chain, cutting down on production expenses and accelerating time to market,” Friedberger continues. “Establishing a digital and sustainable spare parts management operation can increase profitability, as AM eliminates transportation costs and avoids overproduction.

“EOS goes beyond this. Tools such as the EOS Carbon Calculator create transparency and help customers identify the right levers along the entire production workflow. Adding to this, EOS has climate-friendly raw material production, which further helps reduce our customers’ own greenhouse gas (GHG) emissions and lets them achieve their climate targets,” Friedberger emphasises.

Boeing’s Orme notes that AM often uses significantly less material than most other manufacturing technologies. “Because of this, there can be a significant benefit to the environment over the reduction in mining the raw materials, converting the raw materials into ‘printable’ materials, and transporting the raw ‘printable’ materials to the point of use,” she states.

“Additionally, less machining is required so less energy is consumed, less hazardous materials consumed, and there are fewer carbon emissions during the machining steps. Boeing has conducted lifecycle assessments in which a 35 per cent reduction in carbon emissions is estimated for an AM component over a traditionally fabricated (‘hog-out’) of the same component.

“The aerospace and defence industries have the additional sustainability lever in that AM enables the ability to remove weight through novel design. The installed component will therefore be lighter, resulting in lower carbon emissions from the aircraft during service. In fact, a lifecycle assessment conducted at Boeing to demonstrate this assertion illustrated that reducing the weight through additive manufacturing designs of 0.25 lb on one part, resulted in a 19 per cent decrease in carbon dioxide emissions over the life of the aircraft,” Orme reports.

AM might involve a layering process, but it seems the final part adds up to more than the sum of the layers.

This feature was first published in MRO Management – April 2024. To read the magazine in full, click here.