However, the molten metal generates a negative thermal stress following solidification, which produces an in-plane residual stress. This residual stress accumulates toward the upper layer with the repetitive formation process on each layer and often leads to undesirable effects like delamination, cracking, and warpage. Moreover, residual warpage and deformation are asymmetric in nature and scale with the size of the fabricated metal part. As a result, the integrated molding of large metal parts, such as rocket nozzles, is extremely challenging.

To tackle this issue, a team of researchers from Japan and the U.S., led by Professor Akihiro Takezawa from Waseda University, have now proposed an optimized design strategy for AM. "LPBF metal 3D printing, which has been the focus of much attention in recent years, suffers from large warping of molded parts. In this study, we developed a method to reduce residual deformation by simultaneously optimizing the internal structure of the fabricated part and the laser scanning direction," explains Takezawa.

In their study made available online in Additive Manufacturing, the team, including Dr. Qian Chen and Professor Albert C. To from University of Pittsburgh, U.S., studied the reduction of residual warpage while focusing on layer-wise residual stacking and utilized the lattice infill distribution technique.