Powder spreading is an essential procedure in powder-bed-based additive manufacturing, and the resultant packing quality of the powder layer has important effects on the quality of the final products. In this work, the counter-rolling-type powder spreading is investigated by experiments and numerical simulations. Non-invasive in-situ measurements are performed to evaluate the packing qualities of the powder layer such as surface roughness and packing density, where the effect of the spreading speed is studied. It is found that both the surface quality and packing density of the powder layer decrease with the increase of spreading speed. Besides, the sensitivity of the surface roughness of the powder layer increases with the spreading speed, i.e., the higher the spreading speed is, the more remarkably the surface quality decreases. Numerical simulations using the discrete element method are performed to investigate the dynamics of the powder spreading in terms of the velocity, contact force and coordination number of powder particles, providing new insight to the physical mechanisms underlying the counter-rolling-type powder spreading at particulate scale.

粉末铺展是粉末床基增材制造中必不可少的步骤，因此，粉末层的堆积质量对最终产品的质量具有重要影响。在这项工作中，通过实验和数值模拟研究了反向滚动式粉末铺展。进行非侵入性原位测量以评估粉末层的堆积质量，例如表面粗糙度和堆积密度，在其中研究了铺展速度的影响。发现随着铺展速度的增加，粉末层的表面质量和堆积密度均降低。此外，粉末层的表面粗糙度的敏感性随着铺展速度而增加，即铺展速度越高，表面质量下降越明显。