Modeling of powder bed deformation in the binder jetting technology

Abstract

Discrete element modeling of granular media with the binder jetting additive technology is discussed. The main specific feature of this technology is additive buildup of green bodies with thin powder layers that are bonded together with a binder deposited on the areas that correspond to the preset shape of the green body. The technology requires that thickness of the added powder layers is less than three particle diameters. This leads to size effects and precludes the application of continuum modeling. Discrete powder modeling allows the particle rearrangement in powder deposition and spreading in thin layers to be predicted and the density redistribution and shear strains in the powder layers to be evaluated. To provide uniformity of the additive layers, the powder is spread with a blade moving along the powder bed. Distortions of the bonded subsurface elements of the powder bed depend on the blade width: wide blades produce more significant distortions than narrow ones. An empirical equation that relates the distortion of thin-wall green-body elements to the blade width and powder layer thickness in the spreading process is proposed. The distortion is shown to be directly proportional to the amount of the powder removed by spreading with the blade and inversely proportional to the thickness of the added layer. The effect of powder deposition parameters on density distribution in the powder bed is studied. The modeling results are compared with experimental data from binder jetting of ceramic green bodies. All calculations are made with the Open Source Bullet Physics SDK library to model the deformation of granulated media, allowing for friction and energy dissipation in powder particle interactions.