Gas-assisted powder injection molding: A study on the effect of processing variables on bubble formation

The present study incorporates gas-assisted injection molding technology into a Powder Injection Molding (PIM) feedstock. Cylindrical specimens were molded by means of gas-assisted injection molding for a polypropylene random copolymer and powder stainless steel feedstock. Taguchi Design of Experiments (DOE) method was implemented to test the effect of four processing variables on gas bubble permeation. Taguchi L9 based on a three level four variable orthogonal array was implemented for both Moldflow Plastics Insight (MPI) simulations and direct experimentation. Results obtained dictate the order of importance of each of the four processing parameters with respective percent relevance in the process. Taguchi main effect plots were utilized to obtain optimal process settings virtually and experimentally. Optimal processing variables obtained were tested. Experimental signal to noise ratios revealed that gas delay time is the processing variable of paramount importance for the penetration depth of the polypropylene feedstock. In terms of the stainless steel feedstock, experimental signal to noise ratios suggest gas pressure is a highly sensitive parameter.