Structured light-based height control for laser metal deposition

This paper describes a closed-loop geometric control method used to adjust deposition trajectories generated during laser metal deposition (LMD) to the height of a part in different building stages. The usual procedure followed in open-loop Additive Manufacturing (AM) processes consists in generating deposition trajectories based on a CAD model to manufacture the entire part and, once finished, the component is measured to be either rejected or accepted according to previously established geometric criteria. However, there are numerous variables and thermal effects affecting part growth that can result in a failed deposition, regardless of whether trajectories were properly defined in the first place. The proposed measuring system features a structured light scanner that obtains the height profile of the most recently deposited layer. Deposition paths to be followed by subsequent layers are calculated according to point cloud treatments. As a result, deposition is adjusted to the growth of the part at each stage of the process to ensure geometric integrity for components and guarantee process efficiency. Height control can be applied satisfactorily to both powder and wire LMD, to reveal any differences and show effects produced by height deviations in each case.