Improving dimensional accuracy in EBM using beam characterization and trajectory optimization

Managing the dimensional accuracy of parts produced by the Electron Beam Melting process is a challenge. For small dimensions, as in lattice structures (strut diameters), accuracy becomes even more important and geometric quality is linked to mechanical properties. The dimensional quality of parts produced by EBM can be influenced by many process parameters. Simulating the process can help the machine user to choose the best process parameters and improve build dimensional accuracy. The work presented here is based on a method for linking process parameters with beam parameters. Once linked, both sets of parameters are then integrated into a full simulation of the process in order to make trajectory optimization possible. First, this paper explains how the finite element model described in the literature can be improved to simulate the multilayer EBM process. It then describes how this simulation is used to develop a method to characterize the machine beam and determine the link between the focus current and the beam diameter. Finally, it shows how this simulation can be applied to a built shape (vertical strut) hence demonstrating improved accuracy of the produced part.