Pioneering Additive Manufacturing of RF Waveguides

Introduction

Metal additive manufacturing (AM) emerged as a viable production technology in the early 2010s, following a period of evolution as a rapid prototyping tool. This coincided with first reliable solution for producing parts in aluminium. This article documents my involvement in introducing and validating the use of laser powder bed fusion (LPBF) for RF waveguide components, in aluminium, and at a time when such ideas were considered speculative at best.

Early Platform Access: The EOS M280 and AlSi10Mg

When EOS first launched the M280 metal LPBF system, it was the first AM machine capable of producing fully dense metal parts in aluminium. Though work had been carried out by many people with other systems that came before the M280, none had successfully proven fully dense parts were possible, and most laser systems were offered with 200 W laser. The M280 was presented with a 400 W laser, and 3T RPD (now 3T-AM) were the first company worldwide to have this system, and offer AlSi10Mg to industry. Hence, during the period between 2011 and 2014, the opportunity presented itself to collaborate with Astrium (now Airbus Defence & Space) and to present a completely new application for LPBF.

Benchmarking the Unknown: Parallel Innovations in Titanium

It should also be noted, that in the same period, a former leading North American RF communications manufacturer also broke new ground in proving that AM could deliver functional, certified RF components in Ti6Al4V. This work was also a world’s first for the team at 3T RPD, and together with the aluminium parts, helped lay the foundation for what is now a growing standard in aerospace RF engineering.

The Genesis of an Idea: Why just rectangular waveguides?

Astrium were first curious to see if AM could be used to make some simple bracketry and fixtures. Work that by then posed no real difficulty for LPBF. They still needed to learn a lot about the AM process and the potential it had for them. During the initial presentation of the capabilities of LPBF some attention was drawn to waveguide components. However, rectangular waveguide geometries, the standard in RF engineering, were considered to pose some significant challenges for LPBF processes. It was believed that the tight internal corners, unsupported overhangs might lead to stress concentrations, making them difficult to print reliably without distortion and a lot of post-processing.

Recognising this during these early conversations with the design engineers at Astrium, it was proposed that elliptical cross-sections could be a more readily processible alternative. A lot of work had already been carried out to prove that unsupported curved surfaces could be produced via LPBF, and elliptical waveguides were known to perform better than rectangular ones in supporting the necessary mode propagation for RF transmission.

However, at the time metal AM was still viewed with scepticism and it was an uphill struggle to convince people that metal AM could be used for functional RF components. Hence why most applications were limited to mechanical brackets or housings. My suggestion that waveguides, one of the most critical components in satellite communications, could be printed in aluminium was considered radical enough, and so the idea to try elliptical waveguides was temporarily shelved. Fortunately, Astrium did see the potential to experiment with AM, and hence we started a journey to prove materials properties, AM part performance, and to find the first potential production part.

From Concept to Reality: Demonstrating Performance

A structured programme tested the AM process to its limits:

Waveguide geometries were printed in multiple orientations to assess support structure impacts on internal surface quality.
Material properties were characterised through standard metallographic testing.
Test coupons and solid blocks were built across the build plate to examine heat distribution and geometry consistency.
Heat treatment strategies were developed to meet tensile and fatigue performance targets.

The results from materials testing were promising. Better still, RF testing showed that printed parts exhibited return loss and insertion loss values comparable to conventionally made waveguides. This was a critical milestone: it proved that AM could deliver not just form, but function.

However, what remained to be decided was fit, and above all else economy. A solution had to be found that made sense at that time. This meant taking a look at the common bottlenecks in setting up entire waveguide networks on communications satellites. Here the issue of changing direction surfaced. Every junction in a conventional waveguide network involves 2-3 elbow joints. These are assembled using a minimum of 8 small stainless steel bolts and washers and a thin metallic gasket. The operation requires precision manual assembly and testing.

The breakthrough solution was to design a single piece 90-degree twist-bend waveguide in AlSi10Mg offering:

Significant weight savings
Part count reduction
Lower assembly and inspection cost.

Transatlantic Innovation: Ti64 for RF Filters and Multiplexers

Almost in parallel, 3T collaborated with a Canadian company to explore the use of Ti6Al4V (Ti64) for more complex RF components such as multiplexers and filters.

This project presented new challenges. Unlike aluminium, titanium has a higher melting point and lower thermal conductivity, making it more difficult to process via LPBF. Moreover, RF components like filters require extremely tight tolerances and internal surface quality to maintain signal integrity. Therefore, part distortion was a very serious issue that needed to be avoided

After extensive process development, and close collaboration between both companies, we successfully produced functional RF parts in Ti64, establishing:

Inspection and qualification protocols
New scan strategies
Tailored support geometries

This work demonstrated that AM could be extended beyond simple waveguides to more sophisticated RF architectures, opening the door to broader adoption across both aerospace and terrestrial communications sectors. Interestingly, work that followed by the rest of the community in subsequent years concentrated on plastic AM solutions. These all required metallic surface coatings before they could be used, but did lead to a much higher volume of research work. It was from these later projects, that my original idea to make elliptical waveguides finally emerged as potentially successful solutions.

Engineering Leadership and Certification Frameworks

Perhaps the most lasting impact of this journey was the initial creation of documentation to lead to a certification framework for AM RF components. At the time, there were no established standards or documentation protocols for qualifying printed waveguides or filters. This meant that these needed to be produced from the ground up. The first drafts of these documents, which eventually became internal publications within Astrium, included protocols for:

Materials testing tailored to LPBF-produced AlSi10Mg waveguides.
Dimensional and surface quality inspection criteria specific to RF applications.
Documentation templates for process traceability.
Testing compliance to the requirements of launch readiness certification.

Broader Impact and Legacy

The work carried out between 2011 and 2014, as part of an incredible team of engineers and technicians, had a ripple effect across the industry. The introduction of AM waveguides, including the validation of AlSi10Mg and Ti64, and the creation of documentation to certify the end-to-end production process were all firsts in the field.

Key impacts include:

Weight reduction and design flexibility in satellite RF systems, enabling more compact and efficient architectures.
Shorter lead times and lower costs for custom RF components, especially in low-volume, high-value applications.
Global adoption of AM waveguides, with major OEMs and space agencies now routinely using LPBF for RF hardware.

Although the early work I was involved with was covered by NDA and never publicly acknowledged at the time, it laid the groundwork for what followed. A subsequent press release from Airbus in early 2021, stated that they had used 500 RF components, including multi-waveguide blocks and switch network assemblies, for two of Eutelsat’s Eurostar Neo satellites, later launched as Hotbird 13F and 13G. Airbus referred to this deployment as the first large-scale production of RF components via additive manufacturing.

This marked the public recognition of a capability that, years earlier, had only existed in proof-of-concept form. Forever establishing additive manufacturing as a viable pathway for RF engineering.

Conclusion

Looking back, the journey from concept to certified component was both challenging and rewarding. It required not only technical innovation but also cross-disciplinary, and cross-company collaboration, persistence, and a willingness to challenge conventional thinking.

I’m proud that the ideas I introduced during my time at 3T RPD, to use metal AM for waveguides and the qualification of AM RF parts, have since become embedded in the engineering fabric of modern aerospace, and ground-based, communications.

As additive manufacturing continues to push boundaries, I hope this account serves as both a historical record and a source of inspiration for engineers aiming to reshape their industries.

History of AM RF Waveguides