Feed rate modulation for filling macroscopic surface pores in directed energy deposition: an experimental evaluation using boreholes as representative geometries

Abstract

Abstract Investigating new opportunities in additive manufacturing (AM) with porous substrate materials aims to create multifunctional parts. For instance, a porous core can reduce the weight of a part or enhance its damping properties. Meanwhile, the tracks created by laser-based Directed Energy Deposition (DED-LB) with metal powder feedstock shall close the pores and form a transition from the porous core to the non-porous part surface. However, the porous surface of the substrate makes creating consistent tracks challenging, as the melt pool, fed by the powder, must close the pores and build up to the desired track height. Here, we address this challenge through a model-based feedforward controller, which varies the feed rate to control track height and thus modify the final part geometry. Based on the initially measured pore depths, the controller adjusts the feed rate in advance and generates the corresponding G-Code. The as-built tracks are compared to reference tracks manufactured at constant feed rate on the same pore pattern. As a result, the controller compensates for the irregularities through pores, while the reference tracks underperform, particularly for small spacing between pores. Thus, this method appears to be a promising approach to addressing the challenge of working with porous substrate materials when creating multifunctional parts.