Recently, the famous US application lab Lawrence Livermore National Laboratory (LLNL) and the United States well-known private research University of Worcester Polytechnic Institute to develop a new metal 3D printing process - direct metal writing (Direct Metal Writing ).
Currently, most metallic 3D printing processes, such as selective laser melting (SLM), use fine metal powders, which leads to limitations such as gaps or defects in 3D printed parts. Direct metal writing methods can help overcome the limitations of these powder-based metal 3D printing technologies. The new method uses a semi-solid metal, also known as a shear thinning material, without powder. This special metallic material behaves like a solid at rest, but can flow as a liquid when force is applied.
In short, the new method involves heating a metal ingot to a semi-solid state, which is then extruded from a nozzle. The extrusion force makes this shear thinning material liquid sufficiently squeezed out, but when left standing, it behaves like a solid and hardens as the material cools. According to the researchers, this method reduces the amount of oxide and residual stress placed in 3D printed parts.
The study has lasted for three years and was recently published in Applied Physics Letters. The researchers said that this method can be extended to other alloys.
At the moment, direct metal writing is not a perfect solution, and researchers need to address a number of issues, including the ability to make higher resolution parts with "industry-friendly" materials such as aluminum and titanium. In developing this technology, they have been using a bismuth tin mixture that works well because of the lower melting point of this mixture.
"The point is to have a very tight grip on the flow of materials, and now we've done a good job here, and even self-supporting structures can be printed out as never before," said the researchers.
Now, researchers are looking to print an aluminum alloy that, if successful, could be attractive to many manufacturing industries, including aerospace, transportation and more. The main advantage of direct metal writing is the elimination of the time-consuming verification and analysis processes currently required for 3D printed components as well as higher material efficiency.
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