DLR, the German Aerospace Center, is getting ready to launch a parabolic flight that will test a completely new metal powder bed fusion additive manufacturing system for zero-G conditions that has been in development since 2017. The machine is based on a tried and tested principle and designed as a payload for a research rocket. It will be and launched aboard a MAPHEUS rocket for the first time in 2020.
The subject of the DLR research project is the SLS/SLM process (Selective Laser Sintering or Selective Laser Melting), in which the desired component is formed from individual layers of metallic powder using a focused laser beam – layer by layer. The range of possible materials is very wide using this process, even if adjustments to the different machine parameters sometimes require a complex series of measurements.
One of the greatest challenges presented by this process in preparing for lower gravity, all the way up to full weightlessness conditions, is metal powder handling. This includes the targeted application of a densely packed powder layer with uniform thickness, as these parameters determine the quality and material properties of the finished component. This layer must also remain stable on the print bed until the laser process is complete and the next layer is applied. In order to achieve this goal, a gas flow is applied and the individual powder are effectively “sucked” onto the print bed. This method of stabilizing the powder through a pressure range has already been tested in various variations on previous parabolic flights and shows a high level of reliability.
This newly developed additive manufacturing unit for the upcoming experiment is fully automated, has an independent energy supply, it is robust enough to withstand the loads occurring during a rocket launch and it is light in weight. The manufacturing process can be monitored from the ground using a telemetry connection. The rocket payload and ground station will work side by side during the parabolic flight. In addition to testing the hardware for the first time under weightlessness, the experiment will also study the optimizing of system parameters for different, more demanding materials, such as solid metal glasses.
Additive manufacturing, also known as 3D printing, offers a wide range of options for manufacturing components from liquid, powder or filament shaped material. Materials from all classes, including metals, plastics and ceramics, but also composite materials, can be 3D printed. Technical market maturity has been achieved for more and more raw materials.
The advantages of this group of manufacturing processes depend heavily on the process used and the application. All in all, additive manufacturing can be used to manufacture a large number of components or tools from the same starting material, very flexibly and quickly. However one of the most important advantages for using AM in space is the ability to produce parts on location, at the desired location. As a result, applications in space travel – in Earth orbit or beyond, for example on the Moon or Mars bases and during the flights to get there – will be of great interest in the future of human space travel.
Such manufacturing processes, even if they are well-tried and ready for the market on Earth, are by no means trivial to adapt to reduced gravity conditions. On the one hand, there are fundamentally different requirements for the hardware of corresponding production machines, on the other hand, there are often more sophisticated materials that are used in space travel.