Carnegie Mellon University (CMU) and Argonne National Laboratory scientists have found a way to counter defects affecting the 3D printing process.
The researchers have identified how and when tiny gas pockets form in the final product, causing cracks and other failures.
The research has called for a new methodology to predict their formation – information the scientists say could dramatically help improve the 3D printing process.
“The research in this paper will translate into better quality and better control in working with the machines,” contends CMU professor Anthony Rollett.
“For additive manufacturing to really take off for the majority of companies, we need to improve the consistency of the finished products. This research is a major step in that direction.”
The scientists used the extremely bright, high-energy X-rays at Argonne’s Advanced Photon Source (APS) to take super-fast video and images of a process called Laser Power Bed Fusion (LPBF).
As the name itself suggests, LPBF uses lasers to melt and fuse material powder together.
The lasers, which scan over each layer of powder to fuse metal where it is needed, literally create the finished product from the ground up.
Defects can form when pockets of gas become trapped into these layers, causing imperfections that could lead to cracks or other breakdowns in the final product.
Until now, manufacturers and researchers did not know much about how the laser drills into the metal, but assumed that the type of metal powder or strength of laser were to blame for these defects.
This in turn caused manufacturers to use time-consuming and costly trial and error approaches with different types of metals and lasers to reduce such defects.
Now thanks to the new study, scientists can predict when a small depression will grow into a big and unstable one that can potentially create a defect.
“We’re drawing back the veil and revealing what’s really going on,” Rollett said.
During the printing process, the high-power laser changes the melt pool shape to something like a keyhole in a warded lock.
Known to be round and large on top with a narrow spike at bottom, ’keyhole mode’ melting can potentially lead to defects in the final product.
The new research has shown how keyholes form when a certain laser power density is reached that is sufficient to boil the metal.
This also helps reveal the critical importance of the laser focus in the additive manufacturing process, an element that has received scant attention so far, the researchers intone.
Image and content: 3Dnatives/Argonne National Laboratory
