Comparison of roller-spreading and blade-spreading processes in powder-bed additive manufacturing by DEM simulations

Abstract

Abstract The roller-spreading and blade-spreading are main powder spreading methods in powder-bed additive manufacturing. The discrete element method was introduced to simulate nylon powder spreading by both roller and blade spreaders. The two spreading processes were compared from several aspects including particle flow behavior, particle contact forces, forces exerted on spreaders, particle segregation and powder layer density. It is found that powder spreading methods mainly affect the movement trajectory of particles, particle contact forces and forces exerted on spreaders. Complicated dispersion and circulation movement of particles occur inside the powder pile by roller-spreading, while particles have relatively weak dispersion by the blade-spreading. The normal force applied to the roller introduces a compacting effect on the powder pile and creates strong force chains that distribute uniformly in the powder pile. Therefore, the powder bed with higher density can be obtained by roller-spreading in thicker powder layer due to the compacting effect. The blade spreader sustains tangential force mainly, so the blade-spreading process limits its application to thicker powder layer. As the powder layer thickness increases, the roller-spreading is more sensitive to segregation index than that of the blade-spreading. The comprehensive comparison of two spreading processes provides criteria for selecting spreading methods.