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3D Printing has been gaining traction through many scientific and engineering disciplines as an easy way to print complex hierarchical structures, some of which are not possible by other means. The 3D printing of metals, otherwise known as 3D metal printing, is not as widely utilized as other 3D printing areas. Despite this, it is a growing area, and in this article, we look at what 3D metal printing is and the recent developments that have emerged in this field.

3D Metal Printing

3D metal printing is a subset of 3D printing, technically known as additive manufacturing, that is used to print metals into 3-dimensional structures. To understand what a 3D metal printer is, we must first look at 3D printing as a whole.

3D printing is an approach that fuses together different materials into various complex structures, which have previously been designed and pre-programmed, often using computer-aided design (CAD) packages. It is essentially a novel layer-by-layer deposition method that can be designed in three-dimensions.

Now, 3D metal printing, also known as metal additive manufacturing, is a specific 3D printing process that uses metals. Metal 3D printing fuses layers of metals together using a laser. Whilst there are different methods to deposit metals, the general process involves filling a 3D printing chamber with an inert gas (to minimize the oxidation of the metal), followed by depositing a thin layer of metal powder (or pre-melted molten liquid) and fusing the particles with a laser. This process is controlled by scanning the structure with the laser, and the process is repeated until the desired structure is complete.

The different methods to 3D print metals include selective laser sintering (SLS), direct metal laser sintering (DMLS), selective laser melting (SLM), direct energy deposition (DED), laser metal deposition (LMD) and metal binder jetting. In terms of the materials that can be used in 3D metal printing approaches, the number of metals is growing and include aluminium, copper, gold, platinum, titanium and various metal alloys.

Recent Developments in 3D Metal Printing

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Now that the basics on 3D metal printing have been covered, it’s time to look at some of the recent developments that have emerged. More specifically, this section looks at the new research coming out of academia this year where people are using 3D metal printing, with a focus on new 3D metal printing methods and concepts.

Lietaert et al have come up with an interesting proof of concept on how to use meteorites as a printing material for 3D metal printers. The idea looks at the prospect of asteroid mining and using this abundant resource to 3D print spare components, tools and various microstructures aboard spacecraft during missions, to ensure that any components are optimized for the local microgravity. Previous research has already proven that moon regolith can work and this team of researchers have proven this concept using iron-rich meteorites as the manufacturing material. Whilst the research needs more work, the team was able to powder the iron meteorites using gas atomization methods and was able to produce a full structural part. The parts did contain some minor defects, but it showcases a new proof of concept that higher density structures could be made in the future.

In a completely different research area, Behroozfar et al have developed a novel 3D printing approach that has enabled nanotwinned copper to be printed for the first time. The researchers have employed a microscale 3D printing approach at room temperature, that utilizes a localized pulse electrode electrodeposition (L-PED) between two coherent twin boundaries. The nanotwinned copper material printed by the researchers turned out to be fully dense and contained almost no impurities with very little defects. The material also showed no obvious interface between the layers, and after testing, was found to possess good mechanical and electrical properties. This method, and subsequent printing of these materials, have been touted for use across many different applications.

Another novel method has been developed by Deshpande and Hsu. The method has been coined acoustoplastic metal direct-write (AMD) and can be seen as a combination of wire bonding and fused deposition modeling (FDM) approaches. It could also be a new way of 3D printing aluminum structures at room temperature. The researchers have tested the new process by 3D printing millimetre-sized aluminium structures, with the size only being relative to proving its feasibility. The process is considered to be a non-melt method and has so far been proven to create structures that have a density in excess of 99%.

Sources:

All3DP: https://all3dp.com/1/3d-metal-3d-printer-metal-3d-printing/

3T RPD: https://www.3trpd.co.uk/metal-3dprinting.htm

3D Hubs: https://www.3dhubs.com/knowledge-base/introduction-metal-3d-printing

“Meteorite as raw material for Direct Metal Printing: A proof of concept study”- Lietaert K., et al, Acta Astronautica, 2018, DOI: 10.1016/j.actaastro.2017.11.027

“Microscale 3D Printing of Nanotwinned Copper”- Behroozfar A., et al, Advanced Materials, 2018, DOI: 10.1002/adma.201705107

“Acoustoplastic metal direct-write: Towards solid aluminum 3D printing in ambient conditions”- Deshpande A. and Hsu K., Additive Manufacturing, 2018, DOI: 10.1016/j.addma.2017.11.006

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