The nozzle pressure was monitored in a fused filament fabrication process for the printing of high impact polystyrene. The contact pressure, defined as the pressure applied by the newly deposited layer onto the previous layer, is experimentally calculated as the difference between the pressure during printing and open discharge at the same volumetric flow rates. An analytical method for estimating the contact pressure, assuming one-dimensional steady isothermal flow, is derived for the Newtonian, power-law, and Cross model dependence of shear rates. A design of experiments was performed to characterize the contact pressure as a function of the road width, road height, and print speed. Statistical analysis of the results suggests that the contribution of the pressure driven flow is about twice that of the drag flow in determining contact pressure, which together describe about 60% of the variation in the observed contact pressure behavior. Modeling of the elastic and normal stresses at the nozzle orifice explains an additional 30% of the observed behavior, indicating that careful rheological modeling is required to successfully predict contact pressure.

中文翻译：

---

熔丝制造中接触压力的非牛顿模型

在用于打印高抗冲聚苯乙烯的熔融长丝制造过程中监控喷嘴压力。接触压力，定义为新沉积层施加到前一层上的压力，通过实验计算为相同体积流量下印刷和开放放电期间的压力差。假定一维稳定等温流，估计接触压力的分析方法是根据剪切速率的牛顿、幂律和交叉模型相关性推导出来的。进行了实验设计以将接触压力表征为道路宽度、道路高度和印刷速度的函数。结果的统计分析表明，在确定接触压力方面，压力驱动流的贡献大约是拖曳流的两倍，它们共同描述了观察到的接触压力行为中大约 60% 的变化。喷嘴孔口处的弹性和法向应力建模解释了另外 30% 的观察行为，表明需要仔细的流变建模才能成功预测接触压力。