A model-based approach to reduce kinematics-related overfill in robot-guided Laser Directed Energy Deposition

Laser Directed Energy Deposition is an Additive Manufacturing process, which combines the advantages of a high precision and a high deposition rate. Nevertheless, the geometric quality of the produced parts is compromised by unintentional material accumulation, the so-called overfill, at corner sections. This undesired effect results from the kinematics of the system, which includes the trajectory and the traverse speed of the process. By appropriately modeling the process, the overfill can be predicted and compensated by adequately adapting the wire speed. Therefore, this work proposes a pixel-based model, which predicts the overfill based on the trajectory and the traverse speed data provided by the utilized six-axis industrial robot. The presented model predicted the experimentally measured overfill from single beads produced with different corner angles and traverse speeds with an error of less than ± 1 mm³. With the model, the influence of the trajectory and the speed reduction during the process on the overfill was then studied. Furthermore, it was shown that by adapting the wire speed according to the simulation results, the overfill could be reduced to less than ± 2 mm³. Finally, the effectiveness of the approach to facilitate a uniform layer height was demonstrated by manufacturing a multi-layer part, which featured 45° and 90° corner sections. Therefore, this work contributes towards the first-time-right production of additively manufactured parts using Directed Energy Deposition processes.