Particle gradations optimization for powder spreading in additive manufacturing

Optimizing particle gradations to improve the powder bed quality is of practical engineering interest for powder spreading in additive manufacturing (AM). The discrete element model of ceramic powder is introduced to simulate blade-spreading and roller-spreading processes. Based on the packing theory, the effect of particle gradations on the powder bed quality and particle microscopic behavior is analyzed. The results show that fine particle gradations weaken the wall effect. The powder shear dilation in blade-spreading strengthens the loosening effect, however, the compaction effect of roller-spreading weakens the loosening effect. As coarse particle gradations increase, contact force chains become loose, however, strong force arches lead to particle jamming, uneven distribution, and voids in the powder bed. Particle segregation occurs because fine particle gradations pass through the gap between the substrate and spreader, and are deposited at the front part of the powder bed, while coarse particle gradations due to jamming are deposited at the end part of the powder bed. When the particle gradation coefficient is in the range of 0.1 to 0.5, the powder bed quality and particle segregation phenomenon are significantly improved compared to Gaussian distribution. The results can provide valuable references for the selection of particle gradations in AM.