Control of Directed Energy Deposition Process to Obtain Equal-Height Rectangular Corner

Abstract

In the directed energy deposition (DED) process, the scanning speed around sharp corners decreases from the command speed to a capable-curve speed. At a constant powder feed rate, the reduction in the scanning speed causes oversized beads owing to the increased deposition amount per unit time. In this study, the excessive deposition at the corners is controlled by the tailored setting of the corner scanning speed. The proposed control method enables fabrication of an equal-height rectangular corner geometry using the DED process. The bead height along the rectangular corner is controlled to be equal to those of the linear segments. For the sensitivity analysis of the process parameters, the effect of the scanning speed, laser power, and powder feed rate on the bead deposition was investigated experimentally. To generate smooth and equal-height deposition, a corner scanning-speed control algorithm was applied. Results showed that over deposition occurred near the corner section due to the scanning speed drop but after applying the controlled scanning speed, over deposition was decreased. In addition, a three-dimensional thermo-mechanical finite element simulation was performed to investigate the temperature field and induced residual stresses.