SoylentNews is people
SoylentNews
Metal 3-D printing has enormous potential to revolutionize modern manufacturing. However, the most popular metal printing processes, which use lasers to fuse together fine metal powder, have their limitations. Parts produced using selective laser melting (SLM) and other powder-based metal techniques often end up with gaps or defects caused by a variety of factors.
To overcome the drawbacks of SLM, Lawrence Livermore National Laboratory researchers, along with collaborators at Worchester[sic] Polytechnic Institute , are taking a wholly new approach to metal 3-D printing with a process they call direct metal writing, in which semisolid metal is directly extruded from a nozzle. The metal is engineered to be a shear thinning material, which means it acts like a solid when standing still, but flows like a liquid when a force is applied.
[...]Instead of starting with metal powder, the direct metal writing technique uses an ingot that is heated until it reaches a semi-solid state—solid metal particles are surrounded by a liquid metal, resulting in a paste-like behavior, then it's forced through a nozzle. The material is shear thinning because, when it's at rest, the solid metal particles clump up and cause the structure to be solid. As soon at the material moves, or is in shear, the solid particles break up and the system acts like the liquid matrix. It hardens as it cools, so there's less incorporated oxide and less residual stress in the part, the researchers explained.
[...]"The main issue was getting very tight control over the flow," said LLNL engineer Andy Pascall. "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."
More information: Wen Chen et al. Direct metal writing: Controlling the rheology through microstructure, Applied Physics Letters (2017). DOI: 10.1063/1.4977555
(Score: 0) by Anonymous Coward on Sunday April 02 2017, @11:56PM (3 children)
I hope this is an attempt at humor? During the 3D printing process the metal (could be aluminum) is brought to high temp, near to the melting temp. If your scissors (shears) are cutting things at temp near to the melting point of the blades, perhaps you need to use scissors with ceramic blades or some other material that has a higher melting point.
(Score: 1, Redundant) by aristarchus on Monday April 03 2017, @12:25AM (2 children)
Humor? Could be. You don't get it? There is probably an obvious rebuttal for that.
But on the other hand, metallurgically speaking, printing molten metal may sound like fun, but it is difficult for several reasons. One is inertia. Metal above the melting point will not tend to immediately cool enough to hold a pixel. Second is pressure and tempurature. For any useful metal, the requirement for a nozzle to deposit the molten metal are beyond current materials science. So, they came up with this?
As soon at the material moves, or is in shear, the solid particles break up and the system acts like the liquid matrix. It hardens as it cools, so there's less incorporated oxide and less residual stress in the part, the researchers explained.
My point is that if you are relying in shear thinning to get the metal to flow, the same metal could experience the same conditions post printing. And if the temperature conditions for that are not extreme, . . . Sintering is still a better option, as is casting and drop forging.
Good luck trimming the hedgefund with your aluminium shears!!
(Score: 0) by Anonymous Coward on Monday April 03 2017, @12:39AM (1 child)
> Good luck trimming the hedgefund with your aluminum shears!!
Wrong application, those are for trimming hedgehogs.
(Score: 2) by aristarchus on Monday April 03 2017, @04:11AM
Good luck trimming the hedgefund with your aluminum shears!!
Wrong application, those are for trimming hedgehogs.
But only Sonic Hedgehogs, so you need virtual aluminium shears, to avoid the shear
trimmingthinning.