Additive manufacturing: Printing in liquid metal enables furniture-sized aluminium parts to be produced within minutes.
Researchers at the US Massachusetts Institute of Technology (MIT) have developed an additive manufacturing procedure which uses liquid metal and produces large components in only minutes. The new technique called liquid metal printing (LMP) utilises molten aluminium which is poured along a predefined course in a bed of tiny glass balls, where the metal quickly hardens into a 3D structure.
According to the research team, LMP is at least ten times as fast as comparable additive processes. Heating and melting the metal also uses energy more efficiently than other methods do. The MIT already tested the new 3D printing technology for the manufacture of large structures like table legs and chair frames.
The advantage of liquid metal printing over other generative manufacturing processes lies in quickly printing large parts at a comparatively low cost. The disadvantage is a lower resolution. According to the MIT, parts produced using LMP are most suitable for uses in architecture, construction and industrial design, where components of larger structures do not need any overly fine details. The process could also be used effectively for rapid prototyping with recycled metal or scrap, even if there is still development work to be done before recycled material can be used.
Even today, generative manufacturing processes like wire arc additive manufacturing (WAAM) are being used in construction and architecture to produce large structures. As WAAM means that some areas need to be remelted during the printing process, the resulting components are prone to cracks and deformation. By contrast, LMP keeps the metal liquid during the course of the entire process, which avoids the structural problems caused by remelting, as the researchers emphasise in their current study.
“We are thinking about an entire new direction in metal production, which has enormous advantages”, says Skylar Tibbits, associate professor in the Department of Architecture and co-director of the Self-Assembly Lab, and main author of the LMP study. According to her, the critical factors which favour liquid metal printing are the speed and the size of the components, but also repeatability and energy consumption. The disadvantage in terms of surface quality something that has to be accepted, as most of the objects surrounding us in daily life, like tables, chairs or buildings, do not need to be finely structured at all.
High speed manufacturing with aluminium
The team decided to use aluminium for liquid printing, as it is often used in construction and can be recycled efficiently and at low cost. As the molten material is directly injected into a granular substance, no support structures are needed for printing.
The researchers experimented with a series of materials with which to fill the print bed, among them powdered graphite and salt, before deciding on 100-micrometre glass balls. These tiny glass pearls, which need to resist the high temperature of molten aluminium, act as a neutral suspension which allows the metal to cool quickly. “These glass pearls are so small, they feel like silk when you touch them. The powder is so fine that it doesn’t really change the surface properties of the printed object”, says Professor Tibbits.
As the jet presses into the glass pearl powder, it is impossible to observe the molten aluminium directly during the deposition process. To support the LMP process, scientists have therefore developed a numerical model to estimate the amount of material which enters the print bed at any given moment in time.
The institute already printed aluminium frames and parts for tables and chairs, which were strong enough to withstand subsequent finishing. The components produced by LMP can be combined with high-resolution processes and materials, in order to create, for example, functional furniture.
The scientists for example created aluminium frames with various thicknesses, which were stable enough to withstand finishing processes like milling and drilling. Combining LMP and finishing processes, chairs and a table were produced, consisting of rapidly printed aluminium parts at low resolution and other components, such as wooden parts.
With US furniture manufacturer Emeco, the MIT has already attracted an interested party to the new process. “At Emeco, we hail from the world of very analogue manufacturing, so it was really impressive to see how liquid metal printing produces nuanced geometries with the potential for wholly structured parts”, says Emeco managing director Jaye Buchbinder. “Liquid metal printing offers the opportunity to produce metal parts with user-defined geometries and at the same time guarantees a more rapid passing time, which is usually not the case with other printing or shaping technologies. This technology definitely has the potential to revolutionise the way we currently handle metal printing and metal shaping.”
Source: MIT
