Simulation-guided variable laser power design for melt pool depth control in directed energy deposition

Melt pool control is essential in metal additive manufacturing processes since the melt pool geometry directly affects the geometric accuracy and material properties of the fabricated part. While online control of 2D melt pool size has been successfully achieved, controlling the melt pool depth, which cannot be directly monitored during the process, is still an outstanding issue. In this study, a simulation-guided process design framework is developed which enables the possibility of defining a time-series laser power profile that achieves a desired melt pool depth across an arbitrary geometry using just one simulation. This is accomplished by implementing a proportional-integral controller in a thermal finite element simulation that utilizes the laser power to control the melt pool depth. The resulting laser power profile from the simulation can then be used in a real deposition process. Example cases with uniform and site-specific melt pool depth control using the developed method are presented. The results show that melt pool depth can be successfully controlled within the simulation and the developed method can be used to design a laser power profile which can be implemented in an arbitrary part to enhance geometric accuracy and control material properties within a part.