Impact of part thickness and drying conditions on saturation limits in binder jet additive manufacturing
Impact of part thickness and drying conditions on saturation limits in binder jet additive manufacturing
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DOI：
10.1016/j.addma.2020.101127
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发表时间：
2020-05-01
影响因子：
11
通讯作者：
Crane, Nathan B.
中科院分区：
文献类型：
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作者：
Crane, Nathan B.
粘合剂喷射 (BJ) 是一种高构建速率的增材制造工艺，其商业兴趣与日俱增。 BJ 应用的增长是由更细粉末的使用和改进的后处理方法推动的，这些方法可以生产致密、均匀的最终零件。然而，对基本液滴/粉末相互作用的理解相对有限。本文考虑了过程中干燥、零件几何形状和液滴尺寸对关键打印参数（粘合剂饱和度）的影响。在不同的加热条件下，可以打印出不同厚度的零件，并具有一系列的饱和度。打印零件质量与理论零件质量的比率用于检测渗色。在未加热的粉末床中，零件质量在测试范围内 (30%-130%) 随打印饱和度水平线性增加。然而，当粉末在层间加热时，打印饱和度水平范围很宽 (30-80%)，在该范围内增加粘合剂饱和度或液滴体积不会增加零件质量。这种稳定的零件质量对应于精确的零件几何形状，没有渗色，并且可能是由于层间粘合剂溶剂的蒸发增强所致。较小的液滴体积（42 pl）也被证明可以降低未加热粉末床和单层部件的饱和水平。零件质量与打印饱和度和墨滴体积的差异在薄零件中最为明显。这些观察结果得出了一种简单的方法，用于确定厚部件中粉末/粘合剂组合的适当打印饱和度参数。
Binder jetting (BJ) is a high build-rate additive manufacturing process with growing commercial interest. Growth in BJ applications is driven by the use of finer powders and improved post-processing methods that can produce dense, homogenous final parts. However, understanding of the basic droplet/powder interaction is relatively limited. This paper considers the impact of in-process drying, part geometry, and droplet size on a key printing parameter: binder saturation. Parts of varying thicknesses are printed with a range of saturation levels under various heating conditions. The ratio of the printed part mass to the theoretical part mass is used to detect bleeding. In unheated powder beds, part mass increases linearly with printing saturation levels across the range tested (30 %-130 %). However, when the powder is heated between layers, there is a wide range of print saturation levels (30-80 %) over which increasing binder saturation or droplet volume does not increase the part mass. This stable part mass corresponds to accurate part geometries without bleeding and is likely due to enhanced evaporation of the binder solvent between layers. Smaller droplet volume (42 pl) was also shown to decrease saturation levels in unheated powder bed and in single layer parts. The differences in part mass with print saturation and droplet volume are most pronounced in thin parts. These observations lead to a simple method for determining an appropriate print saturation parameter for a powder/binder combination in thick parts.