Eutectic AlSi 3D printing

Metal oxides, being abundant on the surface of the moon and Mars in the form of regolith, can be a valuable resource if processed and manipulated to form useful materials. Separating the metal and oxygen atoms in regolith can be accomplished with a variety of different technologies, and the two products can be collected and used to establish and maintain a human presence on the moon and Mars. The metal that can be extracted is dependent on the local composition of the regolith but iron, silicon and aluminum are nearly always the most prevalent metal species. Once extracted from the regolith, these metal products can be collected and purified to make raw construction material for structures, electrical components, solar cells, robotic or ship components, etc. This project is focused on developing a method for melting and extruding these metals as a first step toward a simple method of 3D printing metals on the moon and Mars. A gas tight crucible “print head” was designed to hold metallic feedstock and extrude molten metal from a small nozzle by applying gas pressure to the inside of the crucible. The crucible was placed in a vacuum chamber with an induction coil surrounding the crucible to apply enough heat to melt the metallic contents. Aluminum and aluminum silicon alloys, having the lowest melting point of the three aforementioned metals, serves as a good starting feedstock material for the development of this technology. The extrusion process was tested by extruding aluminum with a variety of different nozzle sizes and applied pressure to narrow down the range of extrusion widths and consistency that can be achieved. The project was able to successfully extrude material into a mold to form tools and material strength testing coupons from a eutectic composition of aluminum and silicon for further materials characterization.

This project marks the first step in developing this technology for additive manufacturing on the moon and Mars. A simple method for construction using locally-derived materials that requires no moving parts would be a very enabling technology for building the components needed for sustaining human and robotic presence off world. By developing the extrusion print head, and connecting the system to machinery for moving the print head, this technique for 3D printing can be used for large scale construction of buildings or large ship components and/or additive manufacturing of smaller scale components like electrical wires, metal ropes, spare robot parts or tools. The technique of melting the metals using induction heating is a very electrically efficient method for metals processing and provides the benefit of requiring no contact between the coil and the material being heat, leading to increased durability of the system compared to resistive heating. This technique for extruding metals can also be developed for higher melting point metals like iron, steel and pure silicon to allow for stronger structures and even printed solar cells.

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