Initial transient phase and stability of annular laser beam direct wire deposition

Abstract

In this paper the stability of the annular laser beam (ALB) direct wire-deposition process, which enables process symmetry and a well-defined ALB workpiece irradiation proportion (WIP) and related energy input onto the workpiece and the wire surface is considered. Various initial process phase strategies with respect to different initial wire-end positions and WIPs were analysed based on the process visualization and outcome, and the melt pool temperature. It was shown that in addition to a precise synchronization of the mutually time-dependent ALB power, wire and workpiece feeding velocity, the fastest and the most robust transition into a stable stationary process could be achieved with the initial position of the wire-end on the workpiece surface. Additionally, the WIP was shown to have a strong and nonlinear influence on the process stability.