Optimization of green compact forming conditions in metal injection molding

The metal Injection Molding (MIM) process is a key technology which makes it possible to form the complicated parts with a near-net shape. MIM includes several elemental processes such as powder mixing, injection molding, debinding and sintering. Therefore, it is necessary to optimize those processes in order to obtain the sound final products. However, the technology of MIM has not been well established yet, although laboratory work on MIM has been carried out extensively by several researchers. In this study, the optimum injection process which is a very important stage for making perfect products has been investigated by changing the forming conditions such as injection pressure, temperature of slurry material and composition of pellet. A stainless steel SUS304 powder which is widely used for a lot of major products is selected as the experimental material. On the basis of the obtained experimental facts, the optimization is done for the injection process in which defects are not left in the green compacts and the injection is done with the lowest energy. Furthermore, a numerical simulation is executed for the slurry filling behavior using Flow Analysis Network(FAN) method. According to the calculated results, the location of weld line, the arrival time of slurry and the dice-well filling behavior are almost agreed with the experimental ones. For the optimization of injection conditions the numerical simulation using FAN method is found to be useful only for the slurry showing the dice-well filling behavior.