Numerical simulation and experimental investigation on jetting phenomenon in low pressure injection molding (LPIM) of alumina

Filling stage for low pressure injection molding (LPIM) of alumina was simulated with finite element method (FEM). Experimental tests were conducted on alumina feedstock with 60 vol.% powder at temperatures and pressures of 70-100 °C and 0.1-0.6 MPa respectively. The properties of injection molded parts including bulk density and four point flexural strength were measured. Liquid state jetting was observed during cavity filling at high injection temperatures and pressures. When the injection velocity exceeds a critical value (about 150 mm/s in this study), the jetting of feedstock was occurred. This jetting gives rise to a lot of voids in the injected molded parts, which result in the variations of bulk density and flexural strength.