Lei Mingju, Wei Qinghua, Li Mingyang, Zhang Juan, Yang Rongbin, Wang Yanen
Industry Engineering Department, School of Mechanical Engineering, Northwestern Polytechnical University, Xi'an 710072, China.
Xinjiang Institute of Engineering, School of Mechatronic Engineering, Urumchi 830000, China.
Polymers (Basel). 2022 Jul 29;14(15):3081. doi: 10.3390/polym14153081.
The selection of optimal process parameters has a decisive effect on the quality of 3D printing. In this work, the numerical and experimental methods were employed to investigate the FDM printing deposition process of PLA/GNPs nanocomposite. The effect of process parameters on cross-sectional morphology and dimension of the deposited filament, as well as the mechanical property of the FDM printed specimens were studied. The extrusion and the deposition process of the molten PLA/GNPs nanocomposite was simulated as a fluid flow by the paradigm of CFD, the effects of printing temperature and shear rate on thermal-physical properties, such as viscosity and surface tension, were considered in models. Under the assumptions of non-Newtonian fluid and creep laminar flow, the deposition flow was controlled by two key parameters: the nozzle temperature and the nozzle velocity. The numerical model was verified by experiments from four aspects of thickness, width, area, and compactness of the deposited PLA/GNPs nanocomposite filament cross-section. Both the numerical simulation and experiment results show that with the increase of nozzle temperature and nozzle velocity, the thickness, area, and compactness of the deposited filament decreases. While the width of deposited filament increased with the increase of nozzle temperature and decrease of nozzle velocity. The decrease in thickness and the increase in width caused by the change of process parameters reached 10.5% and 24.7%, respectively. The tensile strength of the printed PLA/GNPs specimen was about 61.8 MPa under the higher nozzle temperatures and velocity condition, an improvement of 18.6% compared to specimen with the tensile strength of 52.1 MPa under the lower nozzle temperatures and velocity condition. In addition, the experimental results indicated that under the low nozzle velocity and nozzle temperature condition, dimensional standard deviation of the printed specimens decreased by 52.2%, 62.7%, and 68.3% in X, Y, and Z direction, respectively.
最佳工艺参数的选择对3D打印质量具有决定性影响。在本研究中，采用数值模拟和实验方法研究了聚乳酸/纳米颗粒增强复合材料（PLA/GNPs）的熔融沉积成型（FDM）打印沉积过程。研究了工艺参数对沉积丝材横截面形态和尺寸以及FDM打印试件力学性能的影响。将熔融PLA/GNPs纳米复合材料的挤出和沉积过程模拟为计算流体力学（CFD）范式下的流体流动，模型中考虑了打印温度和剪切速率对热物理性质（如粘度和表面张力）的影响。在非牛顿流体和蠕变层流的假设下，沉积流由两个关键参数控制：喷嘴温度和喷嘴速度。通过对沉积的PLA/GNPs纳米复合丝材横截面的厚度、宽度、面积和密实度四个方面的实验对数值模型进行了验证。数值模拟和实验结果均表明，随着喷嘴温度和喷嘴速度的增加，沉积丝材的厚度、面积和密实度减小。而沉积丝材的宽度随着喷嘴温度的升高和喷嘴速度的降低而增加。工艺参数变化引起的厚度减小和宽度增加分别达到10.5%和24.7%。在较高的喷嘴温度和速度条件下，打印的PLA/GNPs试件的拉伸强度约为61.8MPa，与在较低的喷嘴温度和速度条件下拉伸强度为52.1MPa的试件相比提高了18.6%。此外，实验结果表明，在低喷嘴速度和喷嘴温度条件下，打印试件在X、Y和Z方向的尺寸标准偏差分别降低了52.2%、62.7%和68.3%。
