The flow behavior of the powder layer significantly affects subsequent dynamic behavior and final quality of the parts fabricated via powder bed-based additive manufacturing. High powder layer quality is the key scientific problem and technical difficulty, however, the dynamic flow behavior of powder particles and its relationship between powder layer quality were not well understood. In this paper, the influences of typical factors including process parameters (relative layer height and blade velocity) and powder properties (particle size and surface energy coefficient) on powder layer quality of polyamide 6 were systematically investigated by discrete element method to understand the mechanism of the powder layer packing behavior at the particle scale. The packing density, structure uniformity, normalized layer thickness, and surface uniformity were introduced to quantitatively characterize the powder layer quality. The mechanisms at the particle scale, including the blocking of particle, force arch, particle velocity distribution, and cohesion effect were discussed in detail. The results showed that a decreasing value particle size/layer height can effectively weaken the blocking effect of particles, improving the continuity and stability of powder flow and inducing a dense and uniform powder layer. The particles with high average velocity in the gap between the blade and baseplate will move forward after the blade leaves, significantly reducing the layer thickness and packing density. Meanwhile, the cohesion force was determined by the particle size and surface energy coefficient, and the cohesion effect dominated the flow behavior of the particles with a small particle size d = 10μm or a large surface energy coefficient γ = 0.2mJ/m². These findings can provide useful guidance in understanding the flow behavior at the particle scale and improving the powder layer quality.

粉末层的流动行为显着影响通过基于粉末床的增材制造制造的零件的后续动态行为和最终质量。高粉层质量是关键的科学问题和技术难点，但对粉体颗粒的动态流动行为及其与粉层质量的关系尚不十分了解。本文采用离散元法系统研究了工艺参数（相对层高和叶片速度）和粉末特性（粒径和表面能系数）等典型因素对聚酰胺6粉末层质量的影响，以了解其机理。颗粒尺度下的粉末层堆积行为。堆积密度、结构均匀性、归一化层厚、和表面均匀性被引入来定量表征粉末层质量。详细讨论了粒子尺度上的机理，包括粒子的阻塞、力拱、粒子速度分布和内聚效应。结果表明，减小粒径/层高值可以有效减弱颗粒的阻塞作用，提高粉体流动的连续性和稳定性，形成致密均匀的粉体层。叶片与底板间隙中平均速度较高的颗粒在叶片离开后会向前移动，显着降低层厚和堆积密度。同时，内聚力由粒径和表面能系数决定，d  = 10μm 或大表面能系数γ  = 0.2mJ/m ²。这些发现可以为理解颗粒尺度的流动行为和提高粉末层质量提供有用的指导。