基于颗粒模型的取样钳粉末注射成形

Powder injection molding of sampling clamp based on granular model

基于颗粒模型对粉末注射成形进行模拟,假设粉末为允许有重叠量的刚性体,黏结剂处理成颗粒间的黏性连接,在PFC3D离散元程序中编程模拟取样钳零件的三维粉末注射成形过程。研究结果表明:在型腔中心区域发生颗粒聚集,产生较大的中心压力,颗粒的填充速度矢量呈中心发散性,界面处颗粒密度明显小于中心区域。尖角部分由于较大的注射阻力难以填充,导致颗粒密度不均而使最终产品产生变形。对取样钳零件的实际注射实验表明确实存在粉末颗粒难以进入具有较大阻力的尖角部位而导致尖角区域存在较多黏结剂,型腔中心区域颗粒密集,而贴近型腔壁颗粒稀疏。这种粉末密度分布不均的现象与颗粒模型模拟的结论相符合。

The powder injection molding was simulated based on granular model. The granular was treated as rigid body which can have overlapping and the binder was treated as viscous connection between particles. The 3D powder injection molding of sampling clamp was programmed based on PFC3D. The results show particle gathering and great pressure in the central region of cavity. The filling velocity vectors are divergent in the central region and the particle density of interface is less than central region. The angle region is difficult to fill because of the great resistance, and so this leads to the uneven distribution of powder and the deformation of finished product. The results of injection test show that the powder is difficult to enter the sharp comer region which has large resistance, so there is more binder in the sharp comer region. There are dense particles in center cavity and sparse particles near cavity wall. The uneven distribution of powder is in agreement with the simulation of granular model.