Jiang Bingyan

( State Key Laboratory for Powder Metallurgy, Central South University, Changsha 410083)

Zhong Jue

( School of Mechanical and Electrical Engineering, Central South University, Changsha 410083)

Abstract: To deal with the defects of air trap and defective flow caused by jetting in the process of metal powder injection molding, injection molding experiment is carried out on the heavy alloy tungsten ball research. It is found that the jetting phenomenon takes place at the initial stage of tungsten ball injection molding, and as soon as the feedstock melt enters the mold cavity it will twist strongly. To eliminate the influence of jetting on the metal-powder product, various processing parameters are grouped,  the shear thinning of non-Newtonian flow is applied and the injection molding technology at high speed and heavy pressure is used to make the injection process finished instantly. In addition, the simulation of the injection molding process is conducted by using the Moldflow MPI. The experimental results show that the traditional flow simulating software based on Eulerian method could not be used to simulate jetting process. The idea of modeling and simulation for the jetting process by applying Lagrangian method is put forward. The results of the jetting phenomenon and the practical production experience of the heavy alloy tungsten ball are taken into consideration, venting passage made on the side of the mold parting face at the fixed plate is used in order to increase its venting capacity, and the injection molding technology at high speed and heavy pressure is applied so that quality problem caused by jetting can be solved.

Key words: Jetting  Metal powder injection molding  Simulation  Tungsten ball alloy

CLC No: TG701

国家973重点基础研究发展规划资助项目(G2000067200). Received 20040915, received in revised form 20041230