Additive manufacturing is here to stay—there’s no doubt about that. But just like every other technology, it comes with its own peculiar set of challenges. One of such major challenges is the formation of gas pockets within 3D-printed materials, which tends to weaken the material and cause its structural integrity to fail.
Up until now, researchers and manufacturers didn’t understand how defects come about in 3D-printed materials. They generally assumed that the laser strength or specific type of metal powder being used had something to do with it. So, as expected, most manufacturers have employed a trial-and-error approach, in which they try out various combinations of metals and lasers in an attempt to reduce defects.
However, according to a team of researchers working on a U.S. Department of Energy (DOE) study, the formation of gas pockets in materials actually has nothing to do with the type of laser or metal being used. And these defects can, in fact, be predicted.
With the aid of high-energy X-rays, the researchers were able to observe and record what actually happens during Laser Power Bed Fusion (LPBF)—a process in which material powders are fused together using lasers. As the lasers move across each layer of the powder, it fuses the metals where needed, by drilling holes into the metal to create a melt pool.
Normally, the melt pool should be semicircular or shallow in shape, but during the printing process, high-power lasers—which usually moves at a low speed—can alter the shape of the melt pool into something that looks like a keyhole. This keyhole melting is what encourages the formation of gas pockets, which eventually lead to defects in the printed material.
The researchers stated that keyholes form when the laser reaches a certain power density that is capable of boiling the metal. Therefore, laser focus is of the utmost importance in the 3D printing process, although it has enjoyed very little attention so far. The researchers believe that these findings will encourage the makers of 3D machines to offer more flexible machines, which could significantly improve the quality of the final product. What’s more? The 3D printing process could also get faster for it.
This study was conducted by scientists at the DOE’s Argonne National Laboratory in conjunction with researchers from Carnegie Mellon University. The full details of their findings were recently published in Science.
For more interesting stories about 3D printing, check out Carbon Introduces 3D-Printed Auto Parts for Ford.