Predicting Powder-Polymer Mixture Properties for PIM Design

Powder injection molding (PIM) is a high-volume manufacturing technique for fabricating ceramic and metal components that have complex shapes. In PIM design, it is important to know the injection molding behavior at different powder-polymer compositions so as to understand the trade-offs between ease-of-fabrication, process throughput, and part quality at the design stage. A limited database of materials properties at different powder-polymer compositions is a significant challenge that needs to be addressed in order to conduct accurate computer simulations that aid part and mold design in PIM. However, accurate material property measurements are expensive and time-consuming. In order to resolve these conflicting challenges it is hypothesized that experimental measurements of material properties of a filled polymer at a specific filler content combined with similar measurements of unfilled polymer will be adequate to estimate the dependence of properties on filler content using rule-of-mixture models. To this end, this article focuses on a literature review of experimental data obtained from measurements of rheological, thermal, and mechanical properties for a wide range of powder-polymer mixtures at various filler volume fractions. The experimental data were compared to property estimates using various predictive models. It is expected that the current review will be valuable in selecting appropriate predictive models for estimating properties based on the input data requirements for commercially available mold-filling simulation platforms such as Moldflow® and PIMSolver®. The combined protocol will be useful to design new materials and component geometries as well as optimize process parameters while eliminating expensive and time-consuming trial-and-error practices prevalent in PIM.     

非牛顿流体注射充模过程的谱分析与二维模拟

为计算热塑性材料在薄的中心开口的圆盘注射充模过程的温度场，速度场和压力场，利用切比雪夫配置法和快速富立叶变换，提出了快速收敛和稳定的计算模型，计算结果和实验结果非常吻合，本文考虑了熔体的非牛顿性和过程的非等温性、非定常性以及计算区域的非定常性，对充模过程各时刻都进行了数值分析；对于时间方向的积分采用Ｃｒａｎｋ－Ｎｉｃｏｌｓｏｎ格式，空间方向的积分采用谱方法［１］。     

注塑模充模过程的数值分析

利用非等温、粘性广义Hele－Shaw流动理论,建立了三维薄壁型腔塑料熔体充填过程的数学模型．耦合利用有限元／有限差分法数值求解压力和能量方程,实现充模过程的动态模拟．     

注塑模充模过程动态分析的有限元/控制体积法

塑料熔体在三维薄壁型腔内的流动属于带有运动边界的粘性不可压流体的流动,基于粘性广义Hele-Shaw流动理论,利用控制体积法建立了求解压力场的有限元方程,耦合利用有限元控制体积法自动跟踪熔体的运动边界,实现了充模过程的动态模拟.