Speed Metal

3D printing technologies have proven themselves to be of huge benefit both to individuals and industry in recent years. The ability to create three-dimensional objects layer by layer has transformed a number of fields, ranging from manufacturing to healthcare. Individuals now have the power to turn their creative ideas into tangible prototypes, fostering innovation on a personal level. In industry, 3D printing has streamlined production processes, allowing for more efficient and cost-effective manufacturing. This transformative technology has opened new avenues for customization, rapid prototyping, and even medical advancements such as personalized implants.

However, most 3D printers utilize plastics or resins to produce objects. These materials are of limited strength, and most of them begin to degrade at relatively low temperatures. This significantly limits the applications in which 3D-printed objects can be used. A still emerging area of the field is now focused on creating three-dimensional objects using metals. With their much greater strength and extremely high melting points, printed metal objects could be used in virtually any application.

But it is these very properties of metals that make them hard to work with, hindering the development of new technologies to date. A number of existing metal printing systems do exist today, but they are not very practical for most uses. They tend to be slow and capable of producing only smaller objects. Moreover, some of the techniques require frequent remelting of printed objects, which compromises their structural integrity — and since one of the primary reasons for using metals in the first place is strength, these issues defeat the whole purpose.

A group at MIT has thrown their hat in the ring with an interesting new technology called liquid metal printing (LMP). Printers leveraging this technology can very rapidly print large-scale objects like furniture, often in just a few minutes. Furthermore, prints remain molten throughout the entire process, avoiding remelting issues, which keeps them strong. This technology is far from perfect, however. The speed and scale of the approach comes at the expense of resolution — the prints are very rough and imprecise. This will undoubtedly limit the utility of LMP for many use cases, but areas like architecture, construction, and industrial design, where perfect precision is not always required, could benefit from the approach.

The printing machine contains a graphite crucible where aluminum is melted and stored until needed. It is then deposited through a ceramic nozzle that can move in three dimensions. The molten aluminum is injected into a thick layer of tiny, 100-micron glass beads that fill the print bed. These beads keep the molten aluminum in place until it cools, and also act as supports (you would not want to have to break off aluminum supports, after all).

When the printing process starts, it moves fast. This allows for the rapid production of parts, but it also makes the printing difficult to control. The molten aluminum flows out of the nozzle like water coming out of a faucet, unlike more traditional printers in which small amounts of material are carefully extruded with great precision. As a result, the printed objects have a rough, lumpy appearance and are by no means shaped exactly according to design. But hey, they are close to that design and can be produced quickly, and sometimes that is good enough.

The researchers demonstrated their technology by printing chair frames, table legs, and other large-scale objects. These items were produced within minutes and proved to be strong enough to bear the weight of a person sitting on them, even if they were lacking in beauty.

In the future, the team plans to continue refining their system to eliminate some of the issues that are now present. They want to experiment with new nozzle designs that could give better control over the flow of molten aluminum, and resolve some nagging issues with inconsistent heating that sometimes leads to interruptions in flow. It looks like it will still be a long time before metal printing makes its way into individuals’ homes, but this is a significant step in the right direction.