Numerical Model-Based Control Strategy for Real-Time Heat Input Regulation During Plasma Arc Based Additive Manufacturing

Heat accumulation in metal additive manufacturing (AM) process leads to an increase in the molten pool size along the building direction, which results in nonuniform track morphology, excessive dilution, and even structural collapse. For the purpose of ensuring a stable molten pool size and better geometric accuracy, this work develops an innovative 3-D numerical model-based control strategy to regulate heat input for the AM process in real-time. Specifically, the control strategy involves two steps: (i) a thermal simulation of the deposition process via an intelligent heat source tracking algorithm, thereby outputting a series of heat source data to ensure a constant molten pool size of the 3-D model and (ii) the output heat source data are utilized to regulate heat input point-by-point of the deposit in the subsequent AM process. The proposed control strategy is demonstrated for plasma arc based additive manufacturing (PA-AM) of a 20-layer Inconel 625 thin-walled deposit. The surface quality is measured with a profiler and the deviation of the deposits in the building direction is calculated by image processing techniques. The results show that the proposed control strategy is superior in geometric accuracy compared with the conventional approach (i.e., constant heat input and interlayer temperature). Meanwhile, thermal management of PA-AM through the proposed control strategy reduces the total deposition time and energy consumption by 82.3% and 25.3%, respectively.