Whether it’s building a skyscraper in Dubai or tissue engineering a prosthetic ear in Australia, 3D printing has been driving innovation across countless sectors. From the architects at Cazza Construction retrofitting a crane with 3D printing technology to researchers at Queensland University bioprinting cartilage, the ability to create precise 3D model prototypes in a matter of hours has certainly garnered attention whether you’re a healthcare professional or a civil engineer.
The Direct Metal Writing Technique
The newest in 3D printing comes out of the Lawrence Livermore National Laboratory. Even though in the early stages of their research, scientists have discovered a brand new way to 3D print metal. Poised to revolutionize the manufacturing industry, the team at LLNL collaborating with Worcester Polytechnic Institute (WPI), have deviated from the traditional Selective Laser Melting (SLM) technique in favor of a new approach called direct metal writing.
With a mission to fix the countless drawbacks of the SLM method, LLNL scientists are able to drive semisolid metal directly from a nozzle. According to a Lawrence Livermore news article, “The metal is engineered to be a shear thinning material which acts like a solid when standing still but flows like a liquid when a force is applied.” With powder-based metal printing techniques notorious for gaps and defects in its final prototype, the direct metal writing is a highly precise method – eliminating the potential for defects.
“We’ve advanced a new metal additive manufacturing technique that people weren’t aware of yet,” LLNL materials scientist Wen Chen said. “I think a lot of people will be interested in continuing the work and expanding into other alloys.”
According to the three-year study that was recently published in Applied Physics Letters, the direct metal writing technique replaces the metal powder process in favor of “an ingot that is heated until it reaches a semi-solid state.” From there, solid metal particles are surrounded by a liquid metal, resulting in what the study calls “paste-like behavior” before it’s forced through a nozzle. Since the liquid hardens as it cools, there’s less incorporated oxide and less residual stress in the part.
Revolutionizing Modern Manufacturing
The research and the eventual discovery was not a seamless experience, to say the least. “The main issue was getting very tight control over the flow,” LLNL engineer Andy Pascall explained. “You need precise control of the temperature – how you stir it, how fast you stir – all makes a difference. What we’ve done is really understand the way the material is flowing through the nozzle.”
Using a bismuth-tin mixture with a melting point of less than 300-degrees Celsius, the LLNL team was able to alter the conditions around printing metal directly from a nozzle. Their discovery will enable 3D printing of self-supporting structures, which according to the study, has never been done before. “So much of the work that goes into validation and analyzing for defects would be eliminated,” staff scientist Luke Thornley said. “We can use less materials to make parts, meaning lighter parts, which would be big for aerospace.”
One thing is for sure: the researchers at Lawrence Livermore have certainly paved the way for industries leaders in transportation, aerospace, and consumer technology to grab ahold of their innovation.