University of Wisconsin-Madison engineers mitigate porosity, rough surfaces and large spatters using new beam shaping approach to L-PBF.
Despite its huge potential, metal additive manufacturing has been hindered by certain persistent defects that tend to occur in many 3D printing processes. Fortunately, a team of engineers from the University of Wisconsin-Madison have found a way to mitigate three of the most common issues with laser powder bed fusion (L-PBF) – porosity, surface roughness and large spatters – in one fell swoop.
“Previous research has normally focused on reducing one type of defect, but that would require the usage of other techniques to mitigate the remaining types of defects,” explained Lianyi Chen, associate professor of mechanical engineering at UW-Madison in a press release. “Based on the mechanisms we discovered, we developed an approach that can mitigate all the defects — pores, rough surfaces and large spatters — at once. In addition, our approach allows us to produce a part much faster without any quality compromises.”
The key to the UW–Madison team’s solution is a ring-shaped laser beam provided by nLight, a laser technology company based in Vancouver, WA. Using the ring-shaped beam instead of the usual Gaussian-shaped beam reduced instabilities in the L-PBF process.
Validation of this new approach involved using the Advanced Photon Source, an ultra-bright, high-energy synchrotron X-ray user facility at Argonne National Laboratory. Combining high-speed synchrotron X-ray imaging, theoretical analysis and numerical simulation, the researchers were able to identify the defect mitigation mechanisms that led to the process improvements.
In addition, the UW-Madison team demonstrated that they could use the ring-shaped beam to drill deeper into the material without causing instabilities in the process. This enabled them to print thicker layers, increasing the manufacturing productivity. “Because we understood the underlying mechanisms, we could more quickly identify the right processing conditions to produce high-quality parts using the ring-shaped beam,” Chen said.
The research is published in the International Journal of Machine Tools and Manufacture.
