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Additive Manufacturing in Space
At the moment, all spacecraft are developed, tested, and assembled on earth before being transported by rockets to their respective mission locations. Each component must withstand the high loads of the rocket launch, while the loads of the actual mission are often relatively low. These oversized components cause high space transportation costs due to the high system weight and volume as well as the complex test procedures required for a rocket flight. In order to reduce these costs, spacecraft components could be manufactured and used directly in orbit using generative manufacturing methods.
With this idea in mind, a team of eight students from the University of Applied Sciences Munich decided to prototype a 3D-printing technology through which structures for solar panels, antennas, or any other installation can be created directly in space. Named AIMIS-FYT – AIMIS for Additive Manufacturing in Space – they decided on a printing method in which photoreactive resin is extruded and cured by UV-light.
The Application
The setup basically consists of a primary structure that has a cartesian 3D-print kinematic mounted inside. The printer has two translational axes and one rotational axis. Thus, the printer can move and rotate in one fixed plane. This enables the system to create freeform structures. The print head is the workhorse of the team’s experiment and consists of an extruder driven by a stepper motor, that dispenses a viscous resin when in zero-gravity. During the extrusion process, the resin is simultaneously cured by UV-Light behind the nozzle.
AIMIS-FYT explains how it works: “For our process, we use a so-called “direct robotic extrusion of photopolymers”. It essentially consists of an extruder through which a viscous photopolymer can be dispensed. This allows the resin to be ejected through a nozzle and afterward cured by UV-light. By moving the nozzle externally, it is possible to produce three-dimensional structures. In our case, this is not done layer by layer as in conventional 3D-printers, but directly via a three-dimensional movement in combination with a volumetric extrusion of the resin.”
Solving the Challenge
Unlike conventional FDM printers, the printing process used by AIMIS-FYT prints with a UV-curing resin. This resin needs to be dispensed in a controlled and very accurate manner in order to produce 3D-structures. To meet these requirements, an extruder with a precise stepper motor is used. In addition, the whole setup is required to fit into a small compartment and be useable with the team’s software.
In order to fully benefit from the advantages of the stepper motor, the team decided to use the TMCM-1070 module by Trinamic. “We came across the Trinamic driver module TMCM-1070 already after a short research. This driver module is easy to use, controlled via a step and direction interface, has a very small footprint and is a reliable solution. Furthermore, the module is in a box which easy complies with the requirements for our experimental setup on the Zero-G aircraft,” according to the team from Munich.
First Results
Experiments are based on four basic operations, which have been identified for printing structures (e.g. truss structures) in microgravity. They are ordered according to increasing complexity as followed:
- Straight rod
- Straight rod with start/stop points
- Freeform rod
- Connections between rods
By combining these basic operations, it should be possible in the future to create any customized structural element directly in space.
Zero-Gravity Testing
In November 2019 the AIMIS-FYT team has been selected for the FlyYourThesis2020! campaign, a program of the European Space Agency (ESA), allowing university students to perform scientific and technological experiments under microgravity conditions during several parabolic flights. Throughout the flight campaign in Bordeaux, France, in November 2020, the team from Munich has a total of 90 parabolas to test their technology. During each parabola, they’ll be floating in zero-gravity for about 20 seconds together with their printer.
On three flight days, a total of 90 parabolas will be flown and therefore we can carry out a total of 90 experiments. The experiments are divided into the mentioned four basic operations and within each basic function we test different parameters in order to identify their influence on the printing process. Therefore, we equip our experiment with a variety of sensors, such as thermal imaging cameras, air pressure sensors, temperature sensors, etc. The goal is to print 90 rods of various sizes and shapes, which are analysed in detail afterwards. The results of the experiments will be used to further optimize the printing process and to demonstrate that our additive manufacturing method works under microgravity conditions. In the future, this technology can then be further improved and perhaps even tested in space. The technology offers the opportunity to drastically reduce the costs of satellites and other space missions.
Team AIMIS-FYT: Julius Frick, Christoph Boehrer, Manuel Kullmann, Michael Kringer, Moritz Frey, Fabian Schill, Torben Schaefer, Maximilian Strasser June 16, 2020 / Trinamic / 0
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