Today, virtually all modern rocket engines rely on 3D printing to maximise their performance with tight coupling between structure and function. Students at ETH Zurich have now built a high-speed multi-material metal printer: a laser power bed fusion machine that rotates the powder deposition and gas flow nozzles while it prints, which means it can process several metals simultaneously and without process dead time. The machine could fundamentally change the 3D printing of metal parts, resulting in significant reductions in production time and cost.
The team of six Bachelor’s students in their fifth and sixth semesters developed the new machine in the Advanced Manufacturing Lab under the guidance of ETH Professor Markus Bambach and Senior Scientist Michael Tucker as part of the Focus Project RAPTURE. In a mere nine months, the students realised, built and tested their idea. The machine is particularly aimed at applications in aerospace featuring approximately cylindrical geometries, such as rocket nozzles and turbomachinery, but is also of broad interest for mechanical engineering.
Providing access to advanced technology
Project lead Tucker explains that the project came about from a very specific challenge: developing bi-liquid-fuelled rocket nozzles for ARIS, the Swiss Academic Space Initiative, that is building its own rockets with visions of reaching into space. Within the next few years, ARIS aims to reach the Kármán Line – the internationally recognised boundary of space set at an altitude of 100 kilometres, beyond which the atmosphere is too thin to support flight by aircraft without special propulsion.
In order to withstand the intense heat and pressure over an extended launch, rocket nozzles should ideally be made of multiple metals. For example, their interior can be made of heat-conducting copper with integrated cooling channels and their exterior of a heat-resistant nickel alloy. “For small players like our student rocket team, this sort of multi-material technology has up to now been too complex and too expensive, putting it out of reach,” says Tucker.
Rotational 3D printing
The heart of the new machine is a rotating platform that enables a high-speed printing process. Unlike conventional rectilinear laser power bed fusion machines, where a new layer of powder has to be applied after each layer is melted, the RAPTURE machine works non-stop thanks to its rotating platform. This means that powder is applied and fused by the laser simultaneously, which significantly enhances productivity. This reduces the manufacturing time for cylindrical components by more than two thirds.