Experimental Assessment of a Discrete Element Method Framework for the Numerical Analysis of Powder Bed Additive Manufacturing

Abstract

This paper demonstrates the predictive capabilities of a Discrete Element Method framework with integrated ray tracing by comparing simulations with experiments. To this end, the single scan line formation and the relation to specific process parameters are investigated. Various samples are printed and experimentally analysed, varying the laser power, speed and spot size of the single scan lines. Each sample has an identical substrate with a flat top surface on which the single tracks are printed. The track dimensions, width, depth and height, are measured using profilometry on the full samples and light microscopy on cross-sections. The track formation is analysed through these measurements, assessing stability, melting mode, and track shape.Simultaneously, the printing of single scan lines is simulated by means of a hybrid Discrete Element Method-ray tracing framework. The track dimensions are determined numerically and compared to the experimental results. The numerical framework predicts the height and depth adequately. The track width upon varying laser power and speed shows similar values compared to the experiments. However, the track width for a changing spot size reveals an opposite trend.Finally, the framework is used to predict the effect of using recycled powder on the single scan line dimensions. Different levels of powder degradation are simulated. The laser-powder bed interaction is analysed and used to simulate single tracks, of which the dimensions are determined.

Keywords: Additive Manufacturing, ray tracing, Discrete element method, laser-powder interaction, single scan line