Powder spreading process is to use a spreader such as blade or roller to spread powder layers for subsequent fusion in powder bed fusion additive manufacturing. In this work, the effects of various spreader geometries on powder spreading are examined by discrete element method (DEM). The results show that a compact region in the powder pile exists. Round and inclined surfaces of blade spreaders allow more particles in the compact region to be deposited compared with vertical blades, thus the powder layer formed is denser. However, they exert larger forces on the underlying part. Inhomogeneity of powder layers is caused by particle burst phenomenon, which is due to particle motion conflict in the compact region rather than large forces. Roller system has largest particle motion conflict thus powder layers formed are sparse and inhomogeneous with small layer gaps. Size segregation in blade systems is not as severe as roller systems. (c) 2021 Elsevier B.V. All rights reserved. Powder spreading process is to use a spreader such as blade or roller to spread powder layers for subsequent fusion in powder bed fusion additive manufacturing. In this work, the effects of various spreader geometries on powder spreading are examined by discrete element method (DEM). The results show that a compact region in the powder pile exists. Round and inclined surfaces of blade spreaders allow more particles in the compact region to be deposited compared with vertical blades, thus the powder layer formed is denser. However, they exert larger forces on the underlying part. Inhomogeneity of powder layers is caused by particle burst phenomenon, which is due to particle motion conflict in the compact region rather than large forces. Roller system has largest particle motion conflict thus powder layers formed are sparse and inhomogeneous with small layer gaps. Size segregation in blade systems is not as severe as roller systems.