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.

在金属增材制造过程中，熔池控制至关重要，因为熔池的几何形状直接影响所制造零件的几何精度和材料性能。虽然二维熔池尺寸的在线控制已成功实现，但在加工过程中无法直接监测的熔池深度控制仍然是一个突出问题。在这项研究中，开发了一种模拟引导的工艺设计框架，该框架能够仅通过一次模拟就确定一个时间序列的激光功率分布，从而在任意几何形状上实现所需的熔池深度。这是通过在热有限元模拟中实施一个比例 - 积分控制器来实现的，该控制器利用激光功率来控制熔池深度。然后，模拟得到的激光功率分布可用于实际的沉积过程。文中给出了使用所开发方法进行均匀和特定位置熔池深度控制的实例。结果表明，在模拟中可以成功控制熔池深度，并且所开发的方法可用于设计激光功率分布，该分布可应用于任意零件以提高几何精度并控制零件内的材料性能。