Simulating Powder Bed Based Additive Manufacturing Processes: From DEM Calibration to Experimental Validation

Powder flowability is a critical parameter for additive manufacturing techniques involving powders. In order to obtain thin and homogenous powder layers, a compromise between grain size and flowability has to be found. Unfortunately, when the grain size decreases, the cohesiveness increases and the flowability decreases. Too often, both the powder spreadability assessment and the optimization of printing parameters are costly empiric processes. In this paper, we describe an original method associating GranuDrum powder flow characterization instrument and DEM numerical simulations to asses the process-ability of powders and to optimize printing parameters like recoater speed, layer thickness or recoater geometry. The powder characterization allows to calibrate the simulation parameters and in particular to quantify the inter-grain cohesiveness. Then, the recoating process is simulated with the calibrated simulations to predict the behaviour of the powder inside the printer. In parallel, the results are validated by testing the powder in a printer equipped with an in-situ powder layer homogeneity tester based on image analysis.