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Report & Analysis

3D Printing in Aerospace - Revolution or Evolution?

Overcoming Challenges for Wider Adoption

Report by Frost & Sullivan

Introduction

After highlighting additive manufacturing (AM) as one of the most important technological trends in aerospace and defence, Frost and Sullivan attended the Additive Manufacturing for Defence and Aerospace summit in London in February 2015 to evaluate and align its current research with the industry. Looking at how many people attended this event and the variety of organisations represented (aircraft and engine manufacturers, lower tier suppliers, academics, and so on) the first conclusion is additive manufacturing is clearly drawing a lot of attention. Many attendees and speakers agreed that additive manufacturing will not replace the conventional processes. However, in many cases, it will be a great substitute that will play a major role in the future developments in aviation. The industry perception is that AM will be adopted, but how quickly it will be adopted is the current question. Will AM processes be adopted faster than composite and carbon fibre material on aerospace platforms had been? The military forces could adopt it quicker and drive its evolution in the commercial world as the qualification and certification processes are not as stringent in the forces as they are in commercial aviation. In this market insight, the current achievements of additive manufacturing in the aviation industry have been highlighted, along with the main motivations to implement AM, the major challenges, and the importance of understanding AM as an end-to-end process. Industry stakeholders have identified this as an essential step towards reaching a high level of reliability, driving wider adoption.

Additive Manufacturing, Current Achievements

Adoption of AM is currently still quite low in the aerospace industry. Only a few polymer parts are used in service aircraft. The rate of development of AM varies depending on the material. As AM was first developed for polymers (plastics), the experience acquired on this material is higher than the experience gained on metals. However, due to the original structure of the aircraft, additive manufacturing for metal could maximize gains, such as weight reduction. As a result, aerospace and defence participants are making significant efforts in this direction.

The first firm to produce AM parts for in-service aircraft and use them in commercial flights was Boeing. About 15 years ago it developed an environmental control system duct for the F/A-18, which was later introduced on the Boeing 787. So far, Boeing has produced about 20,000 ducts which are in service. The environmental control system ECS duct is a polymer component developed and produced with Selective Laser Sintering (SLS) machines.

The engine manufacturers, General Electric Aviation (GE Aviation) and its subsidiary Avio Aero, Pratt & Whitney (UTC Group), and Turbomeca (Safran Group) have developed metallic parts for their next generation engines with AM. These engines are soon to be in service.

The most famous example is GE Aviation’s fuel nozzle developed for the Leap engine (CFM International). It was made public in 2012 when GE Aviation decided to acquire Morris Technologies. This part is in cobalt chrome (CbCr) and has been specifically developed with AM in mind. It includes an intricate internal cooling system thus improving the original design. Moreover, originally the nozzle was an assembly of 20 parts and now with the direct metal laser sintering (DMLS) process, it is built from powder layer by layer as a single unit. Not quite yet in full production, it is currently undergoing a series of flight tests. It will reach full production in the early 2020s with about 40,000 fuel nozzles to be produced in a year (19 fuel nozzle per engine). The Leap engine was selected to equip A320 Neo, 737 Max, and Comac C919.

More recently, Turbomeca, a helicopter engine manufacturer, has also announced that it has developed a fuel nozzle. This fuel nozzle will be installed on Turbomeca’s new engine, the Arrano, which is used for test and productions units. The Ardiden 3 combustor swirlers will also be produced with AM leading edge process. To develop this nozzle, Turbomeca has used the selective laser melting technique.

Avio Aero, a subsidiary of GE, has also used an additive manufacturing process, the Electron Beam Melting (EBM) to develop light weight titanium (Titanium Aluminide-TiAl) blades for jet engine low pressure turbines (LPT). These blades have been printed in a different size for every commercial engine of the GE portfolio (leap, GEnx, GE90, and GE9x). This part was tested at the end of the last year on the GEnx engine (the Boeing 787 and 747-8 engine) and will most certainly be produced for the 777-x engine—the GE9x.

These first technological breakthroughs indicate that propulsion systems potentially offer plenty of good components to develop AM as many parts are rather small which is ideal for powder bed systems.

On the defence side, Lockheed Martin employs 400 engineers dedicated to additive manufacturing. During the summit, Lockheed Martin’s presentation mainly focused on AM processes for the development of titanium parts (electron beam melting (EBM), electron beam additive manufacturing (EBAM), and wire and arc additive manufacturing (WAAM), indicating the company’s interest in manufacturing larger parts with AM. As an example, Lockheed Martin already worked on a Flaperon spar, a large titanium part of the F-35 with the EBAM process. Other industry participants (BAE Systems, GKN Aerospace, Airbus, and so on) are investigating metal deposition techniques in order to build larger parts mainly in titanium. As the technology matures and reaches wider adoption, AM will potentially compete with the forging process.

Two conclusions arise from the development and the adoption of AM in the aerospace industry. On one hand, AM parts have been first developed for legacy systems, particularly for those that have gone out of production, (for example, Avro 146, A310). In this specific context, AM allows a quick turnaround in terms of production with a high return on investment. This is because AM usually necessitates only a small production batch and is significantly less expensive than setting up the original and traditional manufacturing process.

On the other hand, AM developments are being driven by new programmes (re-engine options and new platforms) which are currently under development or being fly tested and will soon to be in service (Bombardier Cseries, A320 Neo, 737 Max, C919, 777-X, F-35, and so on). These platforms will be the first to have a few AM parts on board as it is easier and makes more economic sense to implement them in new programs rather than in current ones which have only a few years of production left. Below is an example of adoption of AM parts in re-engine options for the single aisle programmes of Airbus and Boeing.

 

Additive Manufacturing, the Main Motivations

Additive manufacturing is considered to be this century’s leading breakthrough. Not only will it open new manufacturing horizons, it will enable parts and systems optimisation to develop better products for the aerospace industry. Parts, which could not be produced before with the subtractive and conventional manufacturing methods, will now be developed and become a game changer in the aerospace industry.

With AM, lead production time will be reduced as it is more flexible and enables just in time production. For some parts it could be a great advantage, considering the ramp up on aircraft production recently decided by the two main airframe manufacturers. In this context, the possibility to build part quicker is a great advantage. Shorter lead time will also have a direct impact cost wise as it will allow reducing direct production cost in the long term when processes will become more robust. Both the line fit and the aftermarket could benefit from just in time production as it could reduce the amount of parts they store thus decreasing the money capitalized in warehouses and stocks.

Additive manufacturing can also streamline the production as one machine can build a part layer by layer as a standalone unit rather than assembling smaller parts to build the same finished part. Taking out the extra stages of production also creates the opportunity to have only one operator for the AM machine rather than many for each sub-part and one to assemble it. As a result, it reduces the cost of production throughout the supply chain. Ultimately, as parts become more complex and their functionality increases, the total number of parts could decrease requiring less labour force to build the aircraft.

Some AM processes could become an excellent substitute to metal forging, particularly for large titanium parts. These large titanium parts are extremely costly to produce and the lead time is high as there are very few forgers in the world capable of producing these types of parts for the aerospace industry. Moreover, with the increased use of composite (carbon fibre) materials, the proportion of titanium material has increased as well on board. This new process (AM) could open up the market and increase the competition with the forgers resulting in cost reduction.

The reduction of material wastage is another advantage of additive manufacturing. When compared to subtractive processes, AM will use just enough material to build the parts layer by layer limiting surpluses and the quantity of raw material bought. Only when AM powder or wire is more competitively priced, there will be greater cost saving with AM.

With regard to technology improvements, AM gives the opportunity to re-design and optimize (removing unnecessary, unloaded material) the current design as it creates opportunities beyond the current expectation and allows for greater complexity. Adding an extra level of complexity and creating more functionality within a part together form a major incentive for adopting AM. Simply redoing the original parts makes AM too costly.

For example, GE fuel nozzle now includes a cooling function which enhances its performance, that is, it can support higher temperature. In a nutshell, AM gives the ability to build exactly what was developed digitally on CAD software, that is what we see on the screen. With AM processes improving, and engineers becoming more aware of its capability, more complex parts will be designed and fabricated which eventually could lead to a reduction of the total number of parts and as a result to lighter air vehicle. Reducing weight in the aerospace industry is one of the main objectives as it will increase aircraft efficiency, that is, lighter platforms require less power and thrust to fly as a result airplanes will consume less fuel.

Challenges Remain

It has been established that AM could be a game changer for many participants of the aerospace industry. It gives an extra option to build aircraft parts and could result in weight saving and thus lighter and more efficient aircraft, which is essential for the airlines operating them. However, adoption of AM is being slowed down by some challenges. AM is a relatively new technique in the aerospace industry, particularly for metals. To make it even more complex there are plenty of different AM processes or techniques making it harder for the industry participants to choose the right one.

Surface finish is one such challenge voiced by some manufacturers as a reason not to adopt AM yet. Many aerospace parts are in contact with liquid or are directly involved in the drag, thus the specifications for these parts require a high level of surface finish to avoid weakening the aircraft performance. As a result, extra machining and surface treatment are required to ensure high quality of the components that may significantly increase the cost of implementing AM. This is particularly a problem for metal parts as the process is not as well-known as the processes developed for polymers even though the powder bed systems tend to give a relatively good surface finish (buy to fly ratio of close to 1). Fortunately, there are many parts in an aircraft that could start using AM as they do not require a very high level of surface finish.

Some other processes such as the direct deposition have economy issues due to poor surface finish that requires a lot of post processing to remove the extra raw material. As a result, at the moment, the buy to fly ratio of direct deposition is too high (greater than 2). This makes direct deposition economically unsustainable as the costs of the extra material and post processing need to be considered. In order to commercially use direct deposition, the buy to fly ratio for large titanium parts needs to be about 1.5 or at least smaller than 2 and as close as possible to 1. A research group at Cranfield University is developing the wire plus arc additive manufacturing (WAAM) process with the support of some industry participants. Large titanium parts with a buy to fly ratio lower than 2 are expected to be produced through this manufacturing process solving the issue the industry is facing in terms of costs.

Another issue the industry is faced with is the problem to reproduce and repeat parts simultaneously across multiple locations and operators. Certifying parts is a particularly difficult issue for the industry. Even though the difference is not big, not being able to have the same output from the same design raises concern with regard to the ability to produce parts at high production rates with a high degree of accuracy from one production lot to the other.

To add to these challenges, designing parts for additive manufacturing requires specific new skills. At the moment, there is a shortage of engineers with a solid base in additive manufacturing restraining the adoption of the technology. A radical change in mindset is required to design parts specifically for additive manufacturing and not create components that are merely an imitation of conventional manufacturing units. Only a few people are experienced enough to understand additive manufacturing and thus make the most of it. For example, some AM processes require metallurgist capabilities which are quite unique or at least specific. At the moment, lack of knowledge about metallurgy prevents the AM machine from being operated efficiently. Expertise in AM processes and designing is essential for mastering additive manufacturing. Some people have mentioned that one of the principal reasons for GE to acquire Morris Technologies was to acquire the skill set, that is, the people and their expertise as AM skills are in short supply in the aerospace industry. Designing better parts that will result in weight saving is critical to justify the investment in AM, as a result design and skills optimisation are key for AM development. As for every new technology, the aerospace industry needs to prepare for the future by collaborating with universities with established programmes on additive manufacturing and by supporting such programmes in other universities. This will ensure that design engineers have the appropriate skills and will be able to support the industry participants with AM. At the moment, most of the knowledge is gained through on-the-job training.

Another concern that slows down the adoption is the verification, certification, and qualification process. Industry experts see this as one of the most critical challenges as it is often a long and costly process. Qualifying parts requires qualifying each step of the process from the material used to the machine and costs a few million dollars as it is test extensive. Inspection techniques for parts built through conventional manufacturing do not work properly with AM parts, mainly because of the rough surface finish. New specifications need to be written for AM parts. This process is thus very expensive and not every firm can afford to spend this type of money. This reduces the possible number of firms likely to invest in and develop AM, particularly the lower tier suppliers. Moreover, these lower tier suppliers usually receive “orders” from OEMs which tend to restrain them from developing this complex solution. This qualification, certification issue is more of a problem for commercial air vehicles rather than military ones. Involving airworthiness in the early phases of the development facilitates the validation process.

Understanding the End-to-End Process

Overall, the lack of end-to-end process is the key hurdle for a wider adoption of AM in the aerospace industry. Industrials want to understand the process from design to qualification to better control the AM technology

AM brings together, combines directly the design and the manufacturing. This technology pushes the industry towards a design-to-print mind set thus forcing everyone to participate in the conception of an AM part to understand every single aspect of the development, from design to the machine capability and qualification process. Without this overall understanding, it is very challenging to develop a component that is optimise the functioning of a machine and will be certified. The qualification process is very expensive, (in the $ 1 million range), thus facilitation of these operations from the very beginning when designing is a potential solution. Moreover, involving the airworthiness early, proving that at each stage of the development AM complies with their indication will facilitate the process.

In order to understand the end-to-end process, some industry participants that have gained experience about AM have advised new participants to get familiar with AM, by re-doing parts that are currently produced using conventional manufacturing without trying to redesign and optimize it. This will give the opportunity to compare the parts made from conventional and additive manufacturing while gaining experience. Once AM is well known and understood from designing to post processing, finishing, and qualification, it is time to develop a complex part to justify the investment in AM as mentioned previously. This part can now be designed and rethought with the experience gained from redoing a simple part with AM. However, even though this approach is somewhat risk averse and has led to positive outcomes for some participants, it is a very expensive process and only major participants can afford to have this time and money to develop an AM component stage by stage.

Testing remains very expensive and adding this extra stage of development is increasing the cost which cannot be borne by lower tier suppliers, and is very expensive for industry leaders as well.

More collaboration, cooperation, and data sharing among firms could accelerate the adoption of AM as the qualification of AM parts could be done quicker. However, the aerospace industry is a very competitive one where sharing is not really in the DNA. Firms are willing to adopt an open innovation model but mostly to get the idea flowing in rather than sharing internal information.

Conclusion

At the moment, only the premise of a long story between aerospace and additive manufacturing is being witnessed. As mentioned previously, it is not whether AM will be adopted but when. The aerospace industry participants are slowly gaining knowledge and experience about AM and are starting to understand what they can and cannot do with it. The technology is getting better, although there is still a difference in terms of technological readiness for polymers and metals, the former being more advanced. Now it is mainly about understanding the overall process. The first metal AM parts will be flying very shortly on series aircraft. However, only with the next generation of aircraft (end of next decade) will we see a greater percentage of AM parts on board with a wider adoption coming from the military aircraft first.