Industry Days - Additive Manufacturing for RF/Microwave hardware

16 Oct 2018, 07:05 → 17 Oct 2018, 18:50 Europe/Amsterdam

Newton 1&2 (ESA/ESTEC)

After a successful first edition for the Industry Days – Additive Manufacturing for RF/Microwave hardware, we have initiated the preparation of a second edition.

Our main purpose is to trigger the discussion regarding the manufacturing of RF/Microwave parts using additive manufacturing. We are sure that, considering the multi-disciplinary environment we will have, the discussion will be very fruitful.

The format for the Industry Days is the same than previous edition. We will have presentations distributed in two days. To build the agenda, we will open a period for a call for abstract where any potential presenter can summarise the scope of the talk and the benefit for the community.

Based on the abstract the Organising Committee will create the programme.

The event does not have any cost for the participants but we will need you to register through our website.

Looking forward to seeing you at ESA-ESTEC.

The Organising Committee

Tuesday, 16 October

09:00 → 09:30 Reception

09:30 → 09:45 Welcome

09:45 → 10:10 Additive Manufacturing: Research, flight applications, and standardisation

Speaker: Dr Johannes Gumpinger (European Space Agency)

10:10 → 11:00 Round Table

11:00 → 11:30 COFFEE BREAK

11:30 → 12:00 3D Printed Complex Electromagnetic Structures

The inherent design flexibility provided by 3D printing provides an opportunity to design and manufacture microwave components with complex structures and improved overall performance. New requirements, especially for expendable unmanned systems in electronic warfare applications, constantly increase the demand on RF/Microwave devices. Meeting these demands is the main motivation for our recent work. These devices need to provide wideband coverage with good impedance match, stable and symmetrical radiation patterns at high power levels, and increased flexibility, compactness, light weight, conformability, and high levels of monolithic integration at low manufacturing costs.

Specifically, we have developed a 3D printed broadband 6-18GHz beamforming Rotman lens system, capable of scanning over +/- 30 degrees. Moreover, we have worked on improving wideband horn antenna performance in addition to monolithic fabrication and integration. During this work a number of challenges in applying additive manufacturing has been encountered, such as printing technologies, assemblies, and material characterization.

The presentation will cover the Rotman lens and horn developments in general, and look at selected topics related to the challenges associated with 3D printing complex microwave components.

Speaker: Mrs Karina Vieira Hoel (FFI)

12:00 → 12:30 Additive Manufacturing of Modulated Ridge Leaky-Wave Antennas

We are presenting a new topology of dual-polarized leaky-wave antenna, allowing for the full control of its aperture illumination in magnitude and phase. Such an antenna enables to produce any radiation pattern property, for example low SLL as considered in our designs. Prototypes working at K and Ka-bands have been fabricated thanks to SLA additive manufacturing process.

Speaker: Ms Aurélie Dorlé (IETR)

12:30 → 13:00 Metal-Coated 3D-Printed Technology for Low loss, Weight and Cost Distribution Networks in Antennas at Millimeter Wave Bands

The rapid evolution of the 3D printing technology is currently being used in a wide range of engineering applications and has led to the development of very promising 3D electromagnetic structures for millimetre-wave devices in recent years. The researcher community and the industry have focused their attention on this additive manufacturing (AM). 3D printing technique is a novel fabrication process for polymer, metal, and ceramic materials. This technique is an attractive option for innovative and complex part fabrication, customization, compact size, rapid prototyping, lightweight, low cost and mass production time.
This contribution will present a comparison of various metal-coated stereolithography 3D-printed waveguide devices using groove gap waveguide technology, WR10 and WR28. Simulation and prototype measurements will be presented as S-parameter results at millimeter-wave bands. Performances in terms of feasibility, materials selection, metal coating thickness, roughness, losses and weight will be also discussed.

Speaker: Dr Jose Manuel Fernandez Gonzalez (Universidad Politécnica de Madrid)

13:00 → 14:00 LUNCH

14:00 → 14:30 Low-Loss Metal Additive Manufactured Waveguides for Satellite Applications

Upcoming satellite systems will consist of large satellite constellations with up to several hundred satellites in lower and medium Earth orbits (LEO and MEO), where each satellite will typically contain several hundreds of passive RF hardware parts such as waveguide harness, filters and antennas on board. System architectures and designs will also become increasingly complex in geometry, alongside with more stringent requirements on weight and compactness. In order to cope with the demand for shorter lead time of these systems and to keep the cost for the final user acceptable, it is expected that certain RF hardware parts will be replaced by their additive manufactured (AM) counterparts. In this presentation, the results achieved by SWISSto12 in metal Additive Manufacturing are presented. The technique used is Selective Laser Melting (SLM) followed by a proprietary surface treatment process that significantly improves the component’s insertion loss. This process consists of a treatment that reduces the effective surface roughness and porosity, followed by copper and silver plating for further effective conductivity improvement and passivation. Several examples of low-loss SLM waveguide components will be shown in the presentation, which will also include the manufacturing details and the qualification status of the AM hardware.

Speakers: Ms Diane Hoerni (SWISSto12), Mr Mathieu Billod (SWISSto12), Dr Tomislav Debogovic (SWISSto12)

14:30 → 15:00 Advanced Antenna Structures Enabled by Metal Additive Manufacturing

Traditional fabrication methods lead to antennas and RF components that are larger and heavier than required to achieve a desired function. Metal additive manufacturing allows the designer to reimagine how these structures fit within a 3D volume, leading to significant reduction in size and weight for complex antennas and RF components. This talk will discuss a number of antenna structures that have been designed to take advantage of additive manufacturing to achieve significant reduction in size, weight, and part count.

Speaker: Mr Michael Hollenbeck (Optisys)

15:00 → 15:30 Metal 3D printing on S-Band Helix Antenna

The aim of this project has been to identify the potential benefits of the use of metal 3D printing on the S-Band Helix Antenna. In order to assess the benefits, the most complex piece of the antenna, the radiating element, that was previously manufactured by conventional methods like turning, milling and spark erosion has been substituted by a 3D printed aluminum one. The design phase included the RF, mechanical, thermal and manufacturing iterations, and due to the new manufacturing concept the radiating design was optimized in terms of additive engineering. The behavior of the aluminium AlSi10Mg was ensured by tensile test, heat treatment, density, metallography, Xray, Xct inspection, OM inspection and roughness. This process was repeated over several batches just to define the best orientation and geometry. The initial mechanical hypotheses were confirmed after the manufacturing test results. The manufacturing was not only centered in the product, but in the process too like powder control, printing monitoring, or parameters definition. The verification has been performed through the manufacturing of an Engineering Qualification Model EQM, that has been fully tested. The RF campaign was composed of radiation pattern and polarization measurement in anechoic chamber, and return loss and frequency measurements. The results before and after environmental test showed a very accurate values with respect to the design ones. The vibration test were composed of sine, random and shock test at EQM level and durations, obtaining satisfactory results. The good agreement between simulations and test results, together with the satisfactory environmental test campaign surpassed have demonstrated the possibility to substitute the helix radiating element from conventional manufacturing methods by metal 3D printing . And additional flight unit has been manufactured and fully tested showing similar results to the EQM one, providing supporting evidences of the good repeatability of the metal 3D printing method developed Topics: S-band helix antenna, additive manufacturing, qualification campaign, AlSi10Mg,

Speakers: Mr EDUARDO LAPEÑA (TRYO AEROSPACE), Mr ESTEBAN CELEMIN (TRYO AEROSPACE), Mr MIGUEL ESTERAS (TRYO AEROSPACE)

15:30 → 16:00 COFFEE BREAK

16:00 → 16:30 Selective Laser Melting of Antenna-Feed Waveguide Components

This presentation will focus on the development of waveguide components for antenna-feed chains operating from Ku band to Q band through Selective Laser Melting (SLM). The variety of components encompasses feed-horns, ortho-mode transducers, septum polarizers, filters, bends and twists. The design of each component has been conceived in view of the additive manufacturing implementation. The corresponding breadboards have been manufactured in AlSi10Mg without metal coating. Integration of RF functionalities will also be discussed.

Speaker: Dr Oscar Antonio Peverini (CNR-IEIIT)

16:30 → 17:00 RF Feed and Antenna Developments for Space Applications

Caused by the upcoming interest in very high throughput satellites (VHTS), the market for satellites is requesting satellite systems with high transmission capacities and a high number of beams. To realize the data rates needed for big data, antenna systems with large bandwidth as well as high power capabilities are necessary. To meet these requirements, active multiple beam antennas are used. These antenna systems can re-use allocated frequency bands, so that the spectral efficiency will increase significantly. A typical multiple spot scenario consists of a single offset reflector fed by a horn cluster. Single feed per beam feed chains are used to generate one beam with one horn. Especially multiple feed per beam scenarios result in a high number of horns per antenna, hence new demands concerning accommodation, thermal concept, mass, costs and lead time are raised. Additive manufacturing has potential to fulfill the upcoming demands. Because of more degrees of freedom and new manufacturing boundaries, other possibilities for accommodation and especially for mass and cost saving were investigated. Airbus Defence and Space analysed the use of additive layer manufacturing of RF components regarding RF performance as well as savings in thermal, mechanical and financial topics. Besides detailed loss analysis of different materials and waveguide shapes single feed components as well as complete feed chains including network and horn were designed, manufactured and measured. Previous and current results and activities will be presented and discussed. These results are showing the potential using of additive manufacturing for RF space components.

Speaker: Mr Michael Kilian (Airbus Defence and Space GmbH)

Wednesday, 17 October

09:30 → 10:00 The mathematical design and mechanical properties of continuous graded Gyroid cellular structures fabricated by Selective laser melting (SLM)

Functional graded cellular structures (FGCSs) have attracted more and more attention for their outperformed properties compared to uniform counterparts and possess great potential applications in various areas. In this work, a mathematical method used to realize the Graded Gyroid cellular structures (GGCSs) with different gradient counter maps was presented. GGCSs with relative density changing from 10% to 20% as well as the uniform ones were generated and successfully manufactured via Selective laser melting (SLA) technology. The mechanical response of these structures under compressive loads was investigated. Novel deformation properties of the Graded cellular structure with enhanced stiffness and strength were acquired by optimizing density distribution. Further investigation shows that the mechanical properties of graded cellular structures can be customized by optimizing the different proportion of each layer. These significant findings illustrate the high application prospect of graded cellular structures in the lightweight, topology optimization, and crashworthiness industries.

Speaker: Lei Yang (KU leuven)

10:00 → 10:30 An approach towards an optimal, robust design of lightweight structures

ABSTRACT
Within the space industry there is a need for low mass structures in order to reduce costs of materials but also costs of fuel required to get these structures into space. In addition, novel manufacturing methods, like additive manufacturing, allow for the creation of more complex geometries which in turn require a more complex design process. Optimising such structures in terms of mass, while at the same time fulfilling all requirements regarding functionality and allowable values such as stresses, strains and displacements, poses a huge challenge. Gradient-based optimisation strategies, but also evolutionary algorithms are characterised by the curse of dimensionality which leads to a large number of required model evaluations or to the situation where no global optimum can be identified.

For this reason, a novel approach is proposed where the optimisation problem is tackled by a heuristic adaption procedure on element level. During the FE-analysis, the structural requirements like allowable stresses or strains are checked and -if necessary- the thickness and/or material orientation of the element is updated. Access to the element routines in the FE-analysis is therefore a requirement for this strategy for which reason a number of state-of-the-art element routines have been developed and adopted as user element routines to be linked with the commercial FEM software ABAQUS. The optimisation process is performed in an iterative manner, meaning that the external loading is applied in several load portions until the full force magnitudes are active. The main advantage of this approach is the applicability to large and complex FE-models, with the possibility of the structure having multiple local optimums. In addition, the strategy can be used for models involving different kinds of elements, like shell elements including layered composite, sandwich or isotropic (metallic) shell sections, and also fastener elements.

This approach by itself could lead to local concentrations of mass caused by high stresses concentrations. These stresses might be artificial, depending on the constitutive law used, and can occur near sharp corners, boundary conditions or load introduction areas. To reduce these peak masses a smoothing algorithm is developed which smoothes the stress concentrations by averaging over multiple elements. The domain over which smoothing occurs for a specific element depends on a certain maximum distance from the element centroid and the similarity of neighbouring elements with regards to how their stresses change with increasing load. Using this approach, artificial peak stresses can be smoothed out without the risk of oversmoothing and underestimation of stresses. Additionally, stiffness driven stresses can be smoothed or shifted as well with this algorithm.

In order to handle the large amount of data involved in the optimisation process, SQLite-databases are used, which act as a means of exchanging information between the algorithms and the FE-software. With these databases the full optimisation procedure remains traceable and, for example, the convergence behaviour of the process can be investigated. Also, it allows for the model itself and all of its properties and results to be visualised and filtered in an efficient manner. Finally, the layup stored in the database can easily be used for an automated model build, resulting in a complete and robust design/optimisation workflow.

In this work, the theoretical backgrounds, the logic of the workflow and practical issues of the applications are discussed. An industrial example illustrates distinct features of all the process and shows the advantages of the approach for industrial applications.

Speaker: Mr Martijn Schmeetz (INTALES GmbH)

10:30 → 11:00 3D Printed Microwave and Millimetre-Wave Filters at University of Birmingham

The talk will give a review of Birmingham’s research on 3D printed filters in the last four years focussing on the latest results from 3D printed filters at W-band using metallic materials. Our work has explored the benefits of 3D printing technology in a number of areas. 3D printing enables the production of some unusual and complex structures that are difficult to achieve using conventional fabrication techniques. This has led to lightweight and low loss filters based on high-Q spherical resonators demonstrated at X-band . We investigated techniques to enhance the thermal handling capability of the filter by ceramic filling and demonstrated designs with wide spurious-free band . A 500 MHz helical filter was produced based on complex helical resonators with fine-tuned dimensions and in a single structure without any soldering joints . This could potentially lead to resistance to vibration and low passive intermodulation. With ESA we have used 3D printing to produce some complex multi-port signal distribution structures such as a waveguide Butler matrix with integrated filter function and an orthogonal mode transducer . They are convoluted structures that are difficult to build using conventional machining. With our 3D printing partners, we are pushing the frequency of the filters using higher-precision 3D printing techniques. Produced from polymer resin using a stereolithography technique, a 5th-order W-band filter with built-in UG387 flanges achieved a measured insertion loss of 0.4 dB at 90 GHz with a 11% bandwidth . For metallisation, non-radiating slots along current lines were cut in the waveguides. Recently, a similar design was prototyped from steel using a high-precision micro selective laser sintering technique . Slots are no longer required and special considerations were made to avoid overhangs. Effects of metal coating were investigated and the measured insertion loss of 1 dB was achieved at 90 GHz. More detailed design considerations and information about the build quality will be provided in the presentation. (A full abstract with references can be found in the attachment.)

Speaker: Dr Yi Wang (University of Birmingham)

11:00 → 11:30 COFFEE

11:30 → 12:00 Additive manufacturing of high permittivity ceramic-based RF filters

Dielectric materials can be found in RF/microwave filters for a wide range of industrial applications. Compared with other technologies, dielectric resonator (DR) filters offer a perfect balance between performance and miniaturization. These structures are capable of handling high-power levels while providing a quality factor (Q) comparable to that of pure waveguide implementations. In addition, the overall volume of the component is significantly reduced thanks to the use of dielectric materials. For that reason, these filters are emerging as the baseline design for many RF filters used in wireless and satellite applications. Due to the difficulty in machining ceramic blocks, the shapes of the dielectric objects included in RF/microwave filters are usually simple: rods, pucks, rectangular blocks, etc. However, the successful development of additive manufacturing (AM) processes for ceramic materials has opened up new geometrical configurations for filter designers to explore. Consequently, we can expect significant advances in key fields for the space industry due to the additional geometry flexibility provided by AM. Novel RF filter structures optimized for the AM of ceramics, manufactured out of different ceramic materials with permitivities will be presented. A comparison of metallization techniques for ceramic filters and the corresponding results for a monoblock 2-pole TM DR filter out of alumina will be given. Practical considerations on the designing of different ceramic-based RF-filters manufactured with the LCM technology will be explained.

Speaker: Mr Dominik Reichartzeder (Lithoz GmbH)

12:00 → 12:30 Additive Manufacturing for Dielectric Narrowband Filters in C-Band

With the maturing of the additive manufacturing techniques, more and more 3D printed RF hardware is being included in flight programs for space. Even more sensitive structures to manufacturing tolerances, like narrowband filters, are nowadays thought to be fabricated using these techniques. In this contribution, a novel narrowband filter in C-Band manufactured using selective laser melting (SLM) and prepared for its use in the nearest future space flight programs is presented. The filter has been carefully selected and good potential is seen for its manufacturing using 3D techniques, which results in shorter lead time and cost savings in addition to typical 3D manufacturing techniques advantages like mass savings, geometry freedom, etc. This can be achieved nowadays only if some drawbacks from additive manufacturing that consume considerable time and effort are ruled out, like polishing of the internal geometry to improve surface roughness and material conductivity. The candidate device is a narrowband filter in C-Band with dielectric resonators which has already been used for flight programs (manufactured using milling techniques). The fields are concentrated inside and in the vicinity of the dielectrics. Therefore, the ohmic losses caused by the aluminium walls (surface roughness and material conductivity) are greatly reduced and can be considered negligible in comparison with the dielectric losses. In addition, the rougher surface can potentially increase the multipaction threshold of the filter. The filter has been manufactured using selective laser melting (SLM) and traditional milling processes. For both cases, a process workflow until the end item is achieved has been defined (Fig. 1 and Fig. 2). The SLM filter has to be cleaned and leftover burr must be removed. Also, temperature and pressure post-processing is needed as well as a preparation of the connecting surfaces and tapping of holes. On the other hand, time is saved during the assembly stage, since no half shells are to be screwed together. The manufacturing time can be speeded up if more filters are printed simultaneously in the same chamber, whereas this was not possible with traditional milling techniques. This depends of course on the size of the chamber and the distribution of the different parts over the chamber. In this case study, up to four filters could be simultaneously printed, theoretically. Up to now, only two filters at a time have been verified. Overall lead time for this filter using 3D manufacturing techniques is approximately 2-3 weeks, which is already comparable to lead times from milling techniques. Of relevance are also here the costs associated with each manufacturing technique. Manufacturing a filter using additive manufacturing is no longer more expensive than using traditional milling techniques, since simultaneous manufacturing is possible and the costs associated to the assembly of the different parts (labour costs, mounting material) can be greatly reduced. In addition to time and cost savings, a mass reduction of around 25% is achieved for this filter when using additive manufacturing techniques while maintaining the filter performance (Fig. 3). Although low but still likely is the risk of radiation for parts made using milling techniques. This possibility is reduced to null when manufacturing with additive techniques, since the hardware can be made in one part.

Speaker: Mr Jose Lorente (Tesat-Spacecom GmbH & Co. KG)

12:30 → 13:00 New Class of Filters Exploiting Additive Manufacturing Versatility

Additive Manufacturing (AM) is witness of an increasing popularity because of its low-cost, fast prototyping capability and flexibility. The use of such a technology for the manufacturing of RF and Microwave components is not straightforward. Some critical points are related to the high conductivity surfaces and/or small manufacturing tolerances required in some RF/microwave applications. Much effort has been made to adapt 3D printing technologies to the manufacturing of RF and Microwave components, but there is still a lot of work to do. AM technology flexibility does not mean that all geometries are now possible. In fact, AM technology has its own constrains that should be considered at the design stage. In any case, the constrains are different from those of the classic manufacturing technologies. This means that geometries that was not allowed in the past are now possible. In this contribution, some microwave filters exploiting such new geometries are shown. Such new shapes have been used to obtain resonators capable of response with transmission zeros very close to the filter band, filters with in-line geometries capable of transmission zeros and very compact filters manufactured on a very thin septum. All the presented structures are realized by using a 3D printer based on stereolithographic technology, this resulting in plastic printed objects. Such objects need to be metalized and this is done by silver painting and then by copperplating. This technique is now intended for prototyping. The aim of this presentation is to share with the audience such ideas and see if it is possible to improve the quality of the proposed structures by increasing their Technology Readiness Level (TRL) for example by exploiting other AM technologies.

Speaker: Dr Cristiano Tomassoni (University of Perugia)

13:00 → 14:00 LUNCH

14:00 → 14:30 3D Printed Millimetre-wave Components for Spacecraft Payloads

This paper reports on some of the results from a one-year pilot project, funded by the UK Space Agency, to investigate polymer-based 3D printed guided-wave and quasi-optical components for spacecraft payloads. Although satellites have payloads covering a wide range of frequencies, this project focused on G-band (140 to 220 GHz) which is commonly used for weather satellites. A range of components, including straight waveguide sections, rectangular horn antennas, and off-axis parabolic mirrors, have been produced. These components have shown promising measurement results. This demonstrates that the 3D printing technology has the potential to overtake existing machined technologies in the not too distant future for general aerospace applications. At the meantime it is appreciated that further research is required to bring the technology to flight model readiness.

This project was undertaken by a consortium comprising Imperial College London (ICL) and the National Physical Laboratory (NPL). Over the past 5 years, the ICL-NPL team have already demonstrated that the electromagnetic performance of polymer-based 3D printed waveguides at X-band (8.2 to 12.4 GHz) and W-band (75 to 110 GHz) are commensurate with commercial waveguides. In addition, the team have successfully demonstrated many other components, notably X-band variable phase shifters, X-band twisted waveguides, W-band bandpass filters, and rectangular waveguides operating up to 1.1 THz. A brief review of these components will also be given in our talk.

Speaker: Xiaobang Shang (National Physical Laboratory)

14:30 → 15:00 SPACE ATOMIC CLOCK IN ADDITIVE MANUFACTURING

The atomic resonator – also called caesium tube – is a part of the atomic clock and allows to obtain a narrow, accurate and stable resonance used by electronics to lock the quartz oscillator on the atomic frequency. It is composed of an ultra-high vacuum Cs tube containing precision RF-elements. It is mainly composed of vacuum envelop, magnetic shielding, Cs oven, microwave cavity (Ramsey cavity), optical components and supports. Why atomic in additive manufacturing ? For reduction of the mass of the Atomic Resonator (material in Titanium Ta6V, optimization of the volume of vacuum envelop, reduction of number of pieces) and for reduction of the cost (production cost / sale cost). How ? By innovative technologies, identification of the design driver (vacuum function) and complete redesign of the vacuum envelop structure. Principle: The atomic resonator is built by additive manufacturing (with EBM process), structure in two half shell in titanium, copper deposit and mechanical refinishing for other functions: RF, optical then assembly of the two parts in only one step by brazing in a vacuum oven. Consequences: Very important mass reduction (> x2), reduction of number of pieces (250 -> 50), removing of alignment constraint during the integration of the optical and RF parts inside the atomic resonator, moving outside the vacuum envelop the functions without vacuum constraint (magnetic shielding…),accessibility of these functions actually under the vacuum and significant cost reduction (> x5). A demonstrator + sample tests have been manufactured to validate the selected concepts (ultra-high vacuum capability, brazing assemblies, copper / braze material deposit…).

Speakers: Mr Philippe DENIS (THALES AVS France), Mr Philippe FAVARD (THALES AVS France)

15:00 → 15:30 AM for electronic equipment

Hensoldt is a major European player in the field of radar systems and sensor equipment. Within this field, the application of innovative technologies is a main goal for future products. Complementary to the civil areas of electronics the miniaturisation and increasing modularity forces the application of new technologies. One of the most promising technologies is the additive manufacturing process for electronic devices, like “printed circuit boards” [PCB]. Hensoldt was one of the first companies in Europe that had the chance to test this new manufacturing technology. First object of the presentation is to show the first impressions about the possibilities, the obstacles and the way for a successful implementation of NanoDimension technology. Second is to get an overview about the mechanical part of electronic equipment and the impacts of AM to solve future requirements.

Speaker: Joerg Sander (Hensoldt Sensors GmbH)

15:30 → 16:00 COFFEE BREAK

16:00 → 17:00 Open Discussion

17:00 → 17:10 Conclusions and Closing