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Quo Vadis, ALM for Aircraft? – Part 2

How should manufacturers prepare themselves for using additive manufacturing in aircraft?

Part one of this Q&A can be found here.

ALM (Additive Layer Manufacturing, or 3D printing) is now used in broader production. What does this mean for aircraft manufacturers in production and in operations?

Very clearly, significant advances with respect to weight, and assembly and maintenance times can be achieved. However, research must still be performed for suitable materials and for the speed and size of the machines.

What weight savings, energy savings, and possibly time-saving potential could be realized?

In discussions around ALM for aircraft construction, a savings potential of 30 percent to 50 percent compared to a conventional design is often highlighted.

However, possible integration of functions and parts into a single part by means of ALM production also offers great opportunities. To illustrate this: a mounting for a hydraulic reservoir is assembled out of approximately 130 conventional parts. It takes approximately 20 days to produce and assemble these parts. With ALM, a newly designed rack can be printed as a single part in two days. Even if the ALM technology is very expensive in this case, a positive business case results through the time savings during the production and assembly as well as the elimination of expensive tools.

Where could the greatest effects of using ALM in aircraft be achieved? Through which type of ALM processes?

Today, due to the limitations in the assembly space of the existing machines, relatively small single parts are produced. With larger machines, it will also be possible to print large structures, up to complete sections. Through this, many previously individually produced parts could be integrated. This results in few interfaces and fewer fastening parts. The assembly is therefore significantly simplified. Due to the increase in design freedom, new possibilities in aerodynamics and thus in fuel consumption open up.

Where are the limits of using ALM in the aviation sector today?

Every production technology has its own advantages and limitations. For conventional techniques, such as sheet metal working or milling, experience from more than 100 years of progress is available.

In the ALM area, we currently have two main dimensions in which advances can be made. These are the aspects of ‘roles and competencies’ and ‘processes’.

On the topic of roles: in the ALM area, there are still only a very limited number of specialists in design and production, even today. In addition, the experience in the field comprises not even 20 years. The advantages and limits of ALM are therefore not yet fully explored even today. Even the roles of design and production must still be further defined, and partially redefined, in this context. The designer requires a deeper knowledge of the production process and the manufacturer requires additional design capabilities, for example in the case of how to create support structures.

Due to lack of experience in the ALM area, there are only limited training resources available to the designers. This is critical, because without special ALM-oriented training, the designer will complete the design in the same way as for a conventional production technique. In this case, it would only be an expensive replacement for the production technology.

The development of design guidelines with proven and fully developed designs for specific application scenarios will therefore contribute to overcoming the lack of experience.

On the topic of "processes": the advantages of ALM, such as design freedom or weight savings, are contrasted by the high costs of the design and production processes.

An example: in order to save 100 kg of weight in an existing aircraft, conventional aircraft parts must be replaced by approximately 300 kg of printed parts. In order to realize the weight savings in the design, it is necessary to perform a topology optimization for each part, which is a very time-consuming process. Therefore, hundreds of hours are required for the design and approval of the ALM parts.

During the approval process, not only must every part be checked against the design and load requirements, the assemblies and superior assemblies must also meet the requirements. The old replaced parts must be managed in parallel, since not all aircraft in operation is equipped with the ALM parts. This increases the number of parts and configurations to be managed and leads to high administrative expenses.

The change of the shape and size of the new ALM parts often has an effect on the tools required and the assembly process, and possibly the qualifications of the personnel required.

Usually the customer does not reward this expense with higher prices. For existing aircraft programs, there is usually not a business case for replacing conventionally produced parts with ALM parts. Only for a partial redesign, such as a new cabin or a new wing, can it possibly make economic sense to use ALM parts.

Some additional aspects must be observed for using ALM for spare parts: If a spare part is requested more than 100 times per year, it can be more efficient to manage it like a conventional part and keep it in stock. There are two options for infrequently requested parts, printing in the warehouse or printing at the customer. To print in the warehouse, a large investment is necessary – a complete workshop, with an ALM machine and post-processing equipment including personnel, must be present. For printing at the customer, the customer must make the investment.

Furthermore, there are two unresolved problems today - how the quality of the spare part can be guaranteed and how it can be guaranteed that only the quantity of parts paid for is printed. There are several research projects, such as Bionic Aircraft, which are examining these topics.

What does that mean for the process? How should manufacturers prepare themselves?

On the one hand, there are not enough machines today to cover the demand for ALM parts in aviation; on the other hand, there is a lack of suitable materials and qualified personnel. Therefore, in the near term, ALM parts will only play a minor role in the serial production. However, a competition to secure the necessary resources will begin between the large aircraft manufacturers.

Michael Jochen is a senior consultat at CENIT.

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