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.

辊涂和刮刀是粉床增材制造中主要的粉末铺展方法。引入离散元方法来模拟由辊式和刀片式撒布机进行的尼龙粉末撒布。从颗粒流动行为、颗粒接触力、施加在撒布器上的力、颗粒分离和粉末层密度等几个方面比较了两种撒布过程。研究发现，撒粉方式主要影响颗粒的运动轨迹、颗粒接触力和施加在撒粉器上的力。滚涂方式在粉料堆内部发生复杂的颗粒分散和循环运动，而叶片分散方式对颗粒的分散相对较弱。施加到滚筒上的法向力对粉堆产生压实作用，并产生强力链，在粉堆中均匀分布。因此，由于压实作用，在较厚的粉层中通过辊涂可以获得更高密度的粉床。刮刀主要承受切向力，因此刮刀过程限制了其应用于较厚的粉末层。随着粉末层厚度的增加，辊涂对偏析指数的敏感性高于叶片涂膜。两种撒播过程的综合比较为选择撒播方法提供了标准。由于压实作用，在较厚的粉层中通过辊涂可以获得更高密度的粉床。刮刀主要承受切向力，因此刮刀过程限制了其应用于较厚的粉末层。随着粉末层厚度的增加，辊涂对偏析指数的敏感性高于叶片涂膜。两种撒播过程的综合比较为选择撒播方法提供了标准。由于压实作用，在较厚的粉层中通过辊涂可以获得更高密度的粉床。刮刀主要承受切向力，因此刮刀过程限制了其应用于较厚的粉末层。随着粉末层厚度的增加，辊涂对偏析指数的敏感性高于叶片涂膜。两种撒播过程的综合比较为选择撒播方法提供了标准。