This paper presents computational fluid dynamics simulations of the deposition flow during printing of multiple layers in material extrusion additive manufacturing. The developed model predicts the morphology of the deposited layers and captures the layer deformations during the printing of viscoplastic materials. The physics is governed by the continuity and momentum equations with the Bingham constitutive model, formulated as a generalized Newtonian fluid. The cross-sectional shapes of the deposited layers are predicted, and the deformation of layers is studied for different constitutive parameters of the material. It is shown that the deformation of layers is due to the hydrostatic pressure of the printed material, as well as the extrusion pressure during the extrusion. The simulations show that a higher yield stress results in prints with less deformations, while a higher plastic viscosity leads to larger deformations in the deposited layers. Moreover, the influence of the printing speed, extrusion speed, layer height, and nozzle diameter on the deformation of the printed layers is investigated. Finally, the model provides a conservative estimate of the required increase in yield stress that a viscoplastic material demands after deposition in order to support the hydrostatic and extrusion pressure of the subsequently printed layers.

本文介绍了材料挤出增材制造中多层打印过程中沉积流的计算流体动力学模拟。开发的模型可预测沉积层的形态并捕获粘塑性材料印刷过程中的层变形。物理学由具有宾汉本构模型的连续性和动量方程控制，该模型被表述为广义牛顿流体。预测沉积层的横截面形状，并针对材料的不同本构参数研究层的变形。结果表明，层的变形是由于印刷材料的静水压力，以及挤压过程中的挤压压力。模拟表明，较高的屈服应力会导致印刷品变形较小，而较高的塑性粘度会导致沉积层的变形较大。此外，研究了印刷速度、挤出速度、层高和喷嘴​​直径对印刷层变形的影响。最后，该模型提供了粘塑性材料在沉积后所需的屈服应力增加的保守估计，以支持后续印刷层的流体静力和挤出压力。