Numerical and experimental analysis of powder bed homogeneity through multi-layer spreading in additive manufacturing

The generation of a uniform and homogeneous powder bed under various process parameters is essential for ensuring high-quality final products in laser powder bed fusion (LPBF) additive manufacturing. In this work, powder bed homogeneity is analysed using experiments and discrete element method (DEM) simulations. The experimental investigations revealed variation in the particle size distributions in the extreme zones of the spreading platform, indicating segregation within the powder bed. Scaled DEM simulations were carried out to analyse the multi-layer spreading process with a fully modelled dispenser. The results showed that the packing density of the spread layer initially increases during the spreading process and then reaches a constant value of approximately 56%, which is in good agreement with the experimental findings. The simulation results also revealed the variation in the packing density and particle size distribution in different zones of the spreading platform. This study provides detailed analyses of the influence of process parameters such as dosing factor, first layer thickness and recoater velocity on the powder bed homogeneity. Higher dosing factors and increased first layer thickness improve packing density but do not eliminate segregation effects, whereas higher recoater velocities decrease packing density and surface quality while reducing segregation. The findings contribute to a better understanding of the powder spreading mechanism in LPBF and provide insights to improve the overall bed quality.