Effect of particle size distribution on the packing of powder beds: A critical discussion relevant to additive manufacturing
Effect of particle size distribution on the packing of powder beds: A critical discussion relevant to additive manufacturing
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DOI：
10.1016/j.mtcomm.2020.100964
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发表时间：
2020-09-01
影响因子：
3.8
通讯作者：
Gupta, Nikhil
中科院分区：
文献类型：
--
作者：
Averardi, Alessandro;Cola, Corrado;Gupta, Nikhil
几种增材制造（AM）方法使用粉末进料。选择性激光烧结是多功能AM方法的一个例子，使用粉末形式的进料，能够生产聚合物和金属部件。在该技术的变型中，使用激光光斑或电子束来局部烧结或熔化填充的粉末床。在每一层上完成烧结之后，在现有床的顶部上添加另外的粉末，使得下一层可以连接。这种方法的主要挑战是控制粉末床的孔隙率，以便最终部件具有均匀和最大的密度。床层之间填料的均匀性对于优化工艺参数是很重要的。这篇评论的重点是考虑多分散硬颗粒床的填充特性，并确定预期的密度可实现给定的颗粒尺寸和形状分布。模型离散混合物以及连续分布。还讨论了颗粒床的初始构型对其形成高度致密填料的能力的影响。不同颗粒尺寸和形状的混合可用于显著增加填充密度，但也可导致床的分离或离析。通过适当控制颗粒形状和使用宽分布，理论上可以实现接近100%的填充密度，但是在小尺寸尺度下出现的实用性和各种效果阻碍了实现如此高的填充密度。最近的进展已经降低了AM部件质量对填充颗粒床的密度的依赖性，但是对于诸如床的导热性和床中的激光功率的吸收的考虑，填充仍然是重要的。填充床特性的改进知识可以有助于开发用于新材料系统的AM方法。
Several additive manufacturing (AM) methods use powder feed materials. Selective laser sintering is an example of a versatile AM method, using feed material in powder form, capable of producing polymer and metallic parts. In the variations of this technique, a laser spot or an electron beam is used to locally sinter or melt a packed powder bed. After the completion of sintering on each layer, further powder is added on top of the existing bed so that the next layer may be joined. A major challenge in this method is controlling the porosity of the powder bed so that the final part has uniform and maximum density. Uniformity in the packing of bed from one layer to the other is important for optimizing the processing parameters. This review is focused on considering the packing characteristics of polydisperse hard particle beds and the determination of the expected density achievable for a given particle size and shape distribution. Models are presented for discrete mixtures as well as continuous distributions. The effect of the initial configuration of a particle bed on its ability to form a highly dense packing is also discussed. Blending of different particle sizes and shapes can be used to substantially increase the packing density, but can also lead to separation or segregation of the bed. Through appropriate control of the particle shape and use of wide distributions, packing densities close to 100 % can theoretically be achieved, but practicality and various effects that appear at small size scales prevent from achieving such high packing densities. Recent advancements have reduced the dependence of AM part quality on the density of the packed particle bed but the packing is still important for considerations such as thermal conductivity of the bed and absorption of laser power in the bed. Improved knowledge of packed bed characteristics can be helpful in developing AM methods for novel material systems.