Optimization on melt front velocity in powder injection molding

During the mold filling stage of powder injection molding,due to non-uniform melt front velocity,the polymer of melt t will result in the non-uniform contraction,relative low density and warpage of the green.Based on the numerical simulation of the forming phase in powder injection molding,a method used to optimize the injection rate is proposed which can make the melt front velocity more even so that the non-uniform shrinkage is lessened and the density of the green is improved.The relationship be-tween the change of the melt front area and the course of screw was established through the simulation,then the mufti-level points of the cavity were determined.Combining the relation between the injection volume and the screw's position respect to each injection point,a simplified math model was formulated from which the injection parameters were obtained.From the simulation and experiments,it can obtained that by the method,the melt front velocity is more even,the standard deviation of the melt front velocity is changed from 14.6 cm/s to 4.2 cm/s,the density of the green is improved from 5.34g/cm3 to 5.54g/cm3,the sample variance of the green is changed from 0.235 to 0.0823.