The 2.5-year project, which will have a total cost of over €1 million, aims to lay the groundwork for producing “smart” fluid flow probes in optimized geometries by additive manufacturing (AM) in a method known as laser powder bed fusion (LPBF). The consortium partners’ complementary competencies were key to their success in securing the funding. Fraunhofer IGCV has done groundbreaking work in laser co-processing of multiple metals, Aerosint has developed a machine technology that adds multi-material capability to LPBF systems, and Vectoflow has extensive experience designing flow probes for manufacture by LPBF.
Though Vectoflow has already been producing custom, geometry-optimized, single-material flow probes for several years using LPBF, they envisage some clear advantages that multi-material AM could bring to their products. As explains Katharina Kreitz, Vectoflow’s co-director:
To use multiple materials in one printing job opens up a world of possibilities. One immediate need is to directly print thermocouples into probes in the exact shape and position we want, rather than having to stop a build job and place prefabricated thermocouples by hand. We hope to meet this need with the technical competencies of Aerosint and Fraunhofer and with the financial support of the Eurostars grant.
Katharina Kreitz, Vectoflow’s co-director
Flow probes used for jet engine and gas turbine development could be made more accurate and longer-lasting if temperature sensors could be embedded deep within the body of the probe. Traditionally machined flow probes are expensive and often burned beyond use in turbine development and testing because accurate temperature feedback information from within the probe body is not available.
Other useful functionality could be incorporated into flow probes by means of a multi-material manufacturing method. Flow probes that are used as speed sensors (or “pitot tubes”) attached to the fuselage of aircraft have small channels that are prone to blockage by ice in certain weather conditions, with potentially grave consequences. Frozen pitot tubes have been identified as the root cause of several catastrophic commercial airline accidents, including Air France flight 447 from Rio de Janeiro to Paris in 2009. Multi-material LPBF would allow probe manufacturers to build pitot tubes containing complex-shaped 3D printed heating elements that minimize the distance heat must diffuse to reach the speed sensor channels — making it effectively impossible for ice to form or remain frozen within.
These applications are just two among the many in which multi-metal and multi-material LPBF could improve safety, efficiency, and performance of familiar components. However, making LPBF multi-material capable is not trivial. In LPBF, fine powders must be spread in very thin layers prior to being consolidated by a laser. This powder “recoating” process has been accomplished historically using scraper blades or counter-rotating roller systems, which spread the powder in a uniform but non-selective manner over the build surface. Because the current process is non- selective, it cannot do what is required for multi-material LPBF: depositing multiple powders with spatial selectivity in a single layer. Aerosint’s managing director Edouard Moens de Hase explains:
Aerosint’s system enables full control over the placement of voxels of powder from multiple materials, which is a basic requirement for multi-material LPBF. It’s really a paradigm shift with respect to the traditional process, but it’s one that’s completely necessary if we want to make multi-material additive manufacturing scalable and useful other than simply for prototyping. We’re happy to have similarly forward-thinking partners in Vectoflow and Fraunhofer IGCV for this Eurostars project.”
Edouard Moens, Aerosint’s Managing Director
Of course, powder recoating is just one step in the process. Perhaps the more fundamental challenge is processing multiple materials in a single build process. While changing laser power and scanning parameters on the fly to match different materials is feasible through software modifications, there may be physical limits to which materials can be combined without interface cohesion and cracking issues. Still, Christine Anstätt of the Fraunhofer IGCV has successfully co- processed materials previously thought to be incompatible:
The combination of steel and a copper alloy in a single build process was not thought to be possible mainly due to their very different material properties – especially in terms of thermal conductivity and coefficient of thermal expansion. However, by adapting the scanning order, overlap area between the two materials and tuning the process parameters, we were able to build dense bimetallic parts without imperfections.”
Christine Anstätt, Fraunhofer IGCV
By building the Aerosint recoater system into an existing LPBF machine and using the laser material co-processing expertise of Fraunhofer IGCV, the team will build proof-of-concept demonstrator flow probes that will be tested for proper functioning by Vectoflow.
The project will begin in October 2019 and will run for 30 months.
About the Eurostars and the Eureka Network
See information provided here: https://www.eurostars-eureka.eu/about-eurostars https://www.eurekanetwork.org/about-eureka
About Vectoflow
Vectoflow designs and manufactures the industry’s most powerful systems for fluid dynamic measurements. These are based on proprietary modelling and additive manufacturing technologies. Vectoflow supplies measuring systems consisting of the flow probes, the measuring hardware as well as the software. Traverse systems as well as consulting services round up the
About Fraunhofer IGCV
Located in Augsburg, Germany, the Fraunhofer Institute for Casting, Composite, and Processing Technology (IGCV in German) is at the forefront of additive manufacturing technologies, with special emphasis on material qualification, multi-material processing, process simulation, and multi-functional part manufacturing with embedded sensors. Please contact Georg Schlick (georg.schlick@igcv.fraunhofer.de) for more information.
Vectoflow’s process allows for complex, custom, multi-hole probe geometries (left). With multi-material processing thanks to Aerosint’s powder deposition technology (middle) and Fraunhofer IGCV’s multi-metal co-printing (right) expertise, they will be able to directly print temperature sensors and internal heating elements within the probe body.
