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Nov 24, 2023

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At this point in additive manufacturing’s evolution, there is no question of the technology’s relevance for aerospace applications. And we’re not just talking about a singular additive manufacturing

At this point in additive manufacturing’s evolution, there is no question of the technology’s relevance for aerospace applications. And we’re not just talking about a singular additive manufacturing process: aerospace OEMs are increasingly adopting a wide range of 3D printing processes and solutions for a variety of use cases, from Direct Metal Laser Sintering (DMLS), to Fused Deposition Modeling (FDM), to Large-Format Additive Manufacturing (LFAM). In the latter category, Italian company Caracol is well positioned to support aerospace manufacturers for the production of large-format composite tooling and is expanding its know-how and capabilities for the production of large metal structural parts for in-space applications. As we’ll see in more detail, the company’s unique and versatile LFAM solutions—for composite and metal—offer several benefits and are enabling aviation and aerospace players to reach higher levels of innovation and efficiency.

Since its founding in 2017 in Milan, Caracol has become a key player in the LFAM landscape thanks to its application-first approach. In its early days, the company started out as a 3D printing service provider, leveraging its robotic additive manufacturing technology and in-house design and engineering capabilities to produce a series of projects and qualified parts for partners in a range of different industries. From there, the company developed and commercialized its polymer and composite LFAM technology, Heron AM, a 6-axis robotic 3D printer, capable of producing parts with no-scale limits and complex geometries. Since the platform’s launch, it has been eagerly adopted by notable OEMs in advanced sectors.

The large-format Heron AM 3D printing solution, which is based on patented hardware and proprietary software, is compatible with a range of materials (including PP, ABS and PC with glass or carbon fiber reinforcement) and offers several benefits to the aviation and aerospace sectors, including:

More recently, Caracol also entered into the metal AM sphere, and is currently developing a wire arc additive manufacturing (WAAM) system. The technology is being used to produce large-scale metal components, such as non-structural finished parts, prototypes of structural parts for testing and critical components for space crafts. The system is not yet commercialized but is central to several innovative research projects, including one for the space industry that we’ll explore in more detail further along in the article.

In the civil aviation industry, Caracol’s Heron AM solution has enormous potential for the production of composite tooling. For example, the technology has successfully been used to manufacture a trim and drill tool from a glass fiber reinforced ABS as well as a cold lamination tool made from carbon fiber reinforced ABS. Both tools were used in the production and maintenance of aircraft fuselage.

Trimming and drilling tools are used in the construction and maintenance of aircraft fuselage to cut and shape materials like aluminum, titanium and composites. Fuselage components must be precise and meet the strict standards of the aviation industry, so it’s important that aircraft manufacturers have the means to produce high-quality trimming and cutting tools that conform to specifications. Cold lamination tools, for their part, are also an important element in aircraft manufacturing and maintenance. Specifically, they are used by maintenance crews in the repair of fuselage systems in the field to apply a thin protective film layer to the surface of fuselage components, helping to extend the aircraft’s lifespan by protecting from corrosion, scratches and other operational damage.

In the production of these aviation tools, Caracol used the Heron 300+ configuration equipped with a High Flow (HF) extruder. This LFAM system, in its standard configuration without a rail, is capable of printing tools measuring up to three meters in length. Both tools were printed in a single piece, minimizing the need for assembly, and were finished using CNC machining to ensure tight tolerances and an optimal surface finish.

Compared to traditional tooling processes, Caracol’s solution enables aviation manufacturers to reduce material waste (as much as 70-80%), cut tooling weight down (by 80-90% to facilitate transport and storage) and decrease lead times by half (from 12 weeks to 5-6 weeks). This, in turn, leads to a significant cost saving of around 50%.

Caracol is also exploring the use of its technology for cure tooling, particularly for molding thermoset prepregs in segments like eVTOL aircraft (Electric Vertical Take-Off and Landing). Cure tools are used in the carbon fiber lamination process and are typically custom designed based on the end-component’s geometry. In eVTOL aircraft production, these tools are made from high-performance composites, such as polycarbonate with 20% CF reinforcement, and must be able to withstand mid-temperature autoclave processes (up to 180° C and 6 bars in terms of working temperature and pressure). Leveraging LFAM to produce the composite molds directly can cut down on production steps (i.e. no more need for a master model). Moreover, thanks to AM’s design flexibility, the tool can be optimized for weight and handling, facilitating logistics and storage.

“Thanks to its six axes and several-meter-wide arm reach, Heron AM prints cure tools with complex geometries in a single working cycle with no need to assemble,” Caracol explains. “Most of the time after printing, the mold is post-processed with CNC to reach the surface roughness and dimensional tolerances required for its workable surface. This also allows us to equip the mold with grooves for trimming the final component directly in the mold.” In the end, eVTOL aircraft manufacturers can gain a competitive edge and increase production efficiency by turning to LFAM for cure tooling, as it facilitates waste reduction, faster lead times and lower manufacturing costs.

Caracol’s reach in the aerospace industry has also extended beyond composite large-format additive manufacturing: the company is presently advancing the use of metal additive manufacturing for large-scale structural parts for applications in space. Thanks to a collaboration with the space logistics company D-Orbit S.p.A. and the Department of Mechanical Engineering at Politecnico di Milano, Caracol is working on a project to develop pressure tanks that can be mounted on carrier satellites to transport and release CubeSats into orbit. These compact CubeSats are then used for a variety of things, like data collection and research, as well as telecommunications and monitoring operations for both research and commercial applications.

Caracol became involved in the innovative project following a financed tender, TechFast Lombardia (POR FESR 2014-2020). In short, the company has been using its WAAM 3D printing solution—based on a Metal Inert Gas (MIG) welding system—to develop a pressurized tank from a lightweight aluminum alloy (AL2319). The use of AM has already offered several benefits compared to the more conventional process of filament winding, including more complex, optimized designs, less material waste and superior weight reduction. Weight reduction is particularly important for this application, as it can significantly reduce fuel and propellant costs associated with satellite launches as well as reduce the spacecraft’s launch emissions. Caracol’s WAAM process also streamlines the production process by printing parts in a single piece. This eliminates the need for assembly (as well as for shells, cores, mandrels, fittings, etc) and reduces lead times significantly.

This metal AM project is also significant on another level. As Caracol explains, the project partners have also developed a “Digital Flow” that combines software, control and automation to manage the end-to-end process of creating metal aerospace parts. This Digital Flow enables the end-user to “control each process phase within a highly automated and efficient workflow that guarantees repeatability, making WAAM technologies an effective and efficient alternative to traditional manufacturing.”

Caracol’s LFAM solutions for composite and metal materials fit into a larger trend in aerospace AM—literally. The industry is interested in large-format additive manufacturing and is working in cooperation with AM players to overcome existing limitations and challenges to the technology’s implementation in order to maximize its benefits and impact.

One of the biggest challenges today has to do with the lack of technological standards and certification approaches for LFAM, and even AM more broadly. As Caracol says: “robust quality control as well as qualification and certification procedures are needed for AM hardware to ensure quality and consistency. Standards need to be refined and agreed upon across the industry to assure the repeatability, reliability and quality of AM components for aerospace applications.”

In other words, certification processes for LFAM are needed for the technology to be fully viable for the production of structural aircraft components. The main challenge to establishing these certification processes is related to a few factors, including the lack of detailed characterization and AM property databases. Fortunately, ISO and ASTM are developing and evolving a range of AM standards, which will help AM providers to meet the strict requirements of aerospace applications. For example, Caracol’s Heron AM process holds the AS/EN 9100 certification, which guarantees that the stringent quality standards for the production of aerospace applications are met.

Material characterization is also an important issue that needs tackling, particularly when it comes to 3D printed composites. Traditionally manufactured composites have transformed civil and commercial aviation since the 1980s and are commonly used as a more lightweight alternative to metal materials. The ability to 3D print composites could therefore open up even more opportunities for aircraft manufacturers by reducing material waste and by further lightweighting parts through optimized designs. And that’s not to mention the ability to produce composite parts more rapidly and take on low-volume production in a cost-efficient way. With further standardization and validation on this front, composite LFAM could become a widespread—and highly advantageous—solution for aviation.

Ultimately, addressing these challenges will make LFAM platforms increasingly viable for aerospace applications and enable a wider range of aircraft OEMs to reap the benefits of the technology. Benefits like material savings and weight reduction, which translates to lower fuel consumption; more complex designs optimized for performance; part consolidation, which streamlines post-production steps like assembly and quality assurance; more agile production volumes; and ultimately faster lead times and lower production costs.