Effects of Spreading Parameters on Powder Bed Quality

Abstract

Powder bed-based additive manufacturing processes such as laser powder bed fusion, binder jetting, and electron beam melting are commonly utilized in various critical areas such as medical, aviation, and energy. Common to all these operations, the powders are first spread onto the build platform in a layer-by-layer fashion and selectively fused or bound with a suitable method. The quality of the process depends on several parameters, including how the powders are spread onto the build platform. The powder spreading operation, which involves spreading powders on a powder bed with a roller or spreader, is an important step in these operations and can affect various process outputs. In this study, powder spreading is numerically investigated using the discrete element method to determine the effects of layer thickness, rotation, and translation velocities, selected as parameters with a powder spreader roller. To account for the relationship between powder spreading parameters and the powder volume packing fraction, as well as the interactions between particles themselves and between the particles and the build plate, the Hertz-Mindlin contact model, including normal tangential forces, as well as the Johnson-Kendall-Roberts (JKR) contact model, including the effects of surface energy, were added to the numerical model. A Design of Experiment combined with analysis of variance (ANOVA) was utilized to gain a broader understanding of the relationship between process parameters, green density, and dynamic angle of repose.