Modeling of Powder Delivery for Laser Powder Bed Fusion Manufacturing of Functionally Graded Materials

The actual problem in manufacturing functionally graded materials (FGMs) produced in the laser powder bed fusion (LPBF) process remains the controllability of the materials gradient and the properties gradient of the final product. The key element in gradient formation is the delivery system in conjunction with the properties of the powder materials. This paper presents the first preliminary stage of the study, an application of a model based on the discrete element method to simulate several powder delivery systems and the analysis of the results obtained. Two designs of LPBF machine constructions with one and two movable platforms are simulated with and without separation walls. The variants of initial powder material separation were modeled along the longitudinal axis, inclined, and periodic lines. The powder material of the same or different densities and particle sizes was analyzed. The mean diameters of the powder particles in simulations are 0.78 and 0.6 mm, and the ratio of the material densities is 1.0 or 1.5. The 15 multi-stage delivery processes were simulated. The influence of various constructive and material parameters on the segregation (percolation) process and final distribution of powder materials was analyzed. It is shown that constructive elements can be more significant than initial material distribution in controlling the final distribution; limiting percolation in the transverse direction remains a major challenge for the distribution system in gradient control. The results demonstrate the usefulness and suitability of applying simulations with the developed model to the design of the powder delivery system and define a direction for further theoretical and experimental research.