Height Dependent Laser Metal Deposition Process Modeling

Laser Metal Deposition (LMD) is used to construct parts in a layer-by-layer fashion. The heat transfer from the melt region to the solid region plays a critical role in the resulting material properties and part geometry. The heat transfer dynamics can change significantly as the layers increase, depending on the geometry of the sub layers. However, this effect is unaccounted for in previous analytical models, which model only a single layer. This paper develops a layer dependent model of the LMD process for the purpose of designing advanced layer-to-layer controllers. A lumped-parameter model of the melt pool is introduced and then extended to include elements that capture height dependent effects on the melt pool shape. The model dynamically relates the process inputs (e.g., laser power, material mass flow rate, and scan speed) to the melt pool morphology and temperature. A finite element analysis is then conducted to determine the effect of scan speed and track height on the solid region temperature gradient at the melt pool solidification boundary. The results of a simulation study are compared to experimental results in the literature and demonstrate that the model is able to successfully predict changes in melt pool width as track height increases, which single layer models cannot.