Overall, metal 3D printing has made great progress over the years and entered real applications, but compared with traditional machines, the gap is still obvious compared with traditional machines.
The relatively mature process methods for metal 3D printing include SLS/SLM, EBM, BJ, and extrusion.
SLS/SLM is a relatively perfect development, the most competitive process method, many mature manufacturers, the European veteran EOS, Renishaw, the United States Desktop Metal, GE, Digital Metal, domestic Platite, Huashu high-tech, and other manufacturers, all have large equipment/system, Material system includes aluminum alloy, titanium alloy, stainless steel, copper and so on. If they are not short of money, these manufacturers can choose at will.
EBM (electron beam melting) relative to SLS/SLM, because the electron beam requires a vacuum system, so the overall sense manufacturers are relatively few. GE acquired the well-known Arcam and became a member of GE. In China, Qingyan Wisdom Beam of Tsinghua Department and Northwest Colored Institute have also launched electron beam manufacturing systems. The advantages of electron beams over lasers include fast scanning speed and adaptability to more types of metal powders (conducting electricity is enough, but the laser must consider the energy absorption rate of the material).
BJ (binder injection) has been valued for its high efficiency in recent years, and has rapidly expanded its sphere of influence, and has penetrated from sand to metal materials, represented by ExOne. Compared with SLS/SLM and EMB, BJ’s efficiency is an order of magnitude improvement, so from the perspective of efficiency and cost, it is more promising. The domestic Chinese science department’s easy system and Beijing’s Longyuan have launched relevant systems.
Extrusion is similar to FDM, using, for example, a thermoplastic resin mixed with a metal powder, extruded from the nozzle, and stacked to form. Compared with the previous several processes, the extrusion process has lower precision.
There is also the arc process, which has been particularly hot in the past two days, Relativity Space’s Terran 1 is printed by arc, which must be processed after processing, otherwise the surface is rougher.
So far, the mainstream process of metal 3D printing is SLS/SLM, which has a high cost and low surface roughness, so it has not been applied on a large scale. Still, many aerospace research institutes have established specialized 3D printing factories and have the capacity for mass production. In contrast, its rapid and complex molding capabilities make up for the shortcomings of low accuracy and high cost.
The congenital deficiency of the powder bed powder process determines that the current process method may be difficult to improve the surface quality, and in the long run, metal 3D printing looks forward to the emergence of new process methods.
