Researchers from Lawrence Livermore National Laboratory are developing “direct metal writing” to improve the process of 3D printing metals.

Whether you’re manufacturing aeroplanes or 3D printers, creating metal parts efficiently is important. For 3D printing to really give traditional methods a run for their money, the technology needs to offer a more reliable metal printing option.

Direct metal writing is a process in development by Lawrence Livermore National Laboratory researchers and collaborators at Worcester Polytechnic Institute. As part of an ongoing three-year study, the researchers have come up with some interesting results.

Their work could offer a new way of creating flawless metal 3D prints. Direct metal writing works by extruding “semisolid metal” from a nozzle. This metal is a “shear thinning material” meaning it is solid when standing but can flow like a liquid under pressure.

Currently there are many issues with powder-metal 3D printing such as gaps or defects. However, Wen Chen, lead author and LLNL materials scientist, explains why he’s so positive about direct metal writing.

“We’re in new territory,” he said, “We’ve advanced a new metal additive manufacturing technique that people aren’t aware of yet. I think a lot of people will be interested in continuing this work and expanding it into other alloys.”

Although this new method has some promising results, the researchers warn that it is still in the early stages. More work is needed before higher resolution parts can be made using better materials.

More Work is Needed on Direct Metal Writing

This method could replace powder-based metal techniques. Direct metal writing uses an ingot (or block of metal) and heats it. The metal then reaches a semisolid state where it will perform like a paste, allowing it to be pushed through a nozzle.

The researchers explain that the material hardens when it cools down. This means less oxide and residual stress in the final print. They used bismuth-tin mixture for their tests but it took some time to get right. LLNL engineer Andy Pascall explains:

“The main issue was getting very tight control over the flow,” he said, “You need precise control of the temperature. How you stir it, how fast you stir it, all makes a difference. If you can get the flow properties right, then you really have something. What we’ve done is really understand the way the material is flowing through the nozzle. Now we’ve gotten such good control that we can print self-supporting structures. That’s never been done before.”

After this success, the team are now moving onto aluminium alloys which pose the difficulty of high melting points. However, staff scientist Luke Thornley, who worked on engineering the material, explains the benefits of this process.

“Being able to print parts out of metal in this way is potentially important,” he said, “so much of the work that goes into validation and analyzing for defects would be eliminated. We can use less material to make parts, meaning lighter parts, which would be big for aerospace.”

Source: Lawrence Livermore National Laboratory