| Abstract: | Most of the commercially available computation programs for injection molding use restrictive assumptions which lead to simple mechanical and thermal equations. These computations are generally sufficient to predict the flow distribution in the mold but the pressure and temperature distributions are not precise. Our aim was first to model very accurately the filling stage of several molds of elementary geometries. For this purpose, a two-dimensional model has been built which solves at each time step the finite difference forms of the continuity, momentum, and energy equations. A refined grid is used near the mold walls to take into account the great temperature gradients. These models have been validated by comparing the pressure field with experimental measurements. The precision of the model is better than 15 percent for several mold geometries and several injection conditions. In a second step, molds of complex geometries have been analyzed by assembling elementary geometries. The flow distribution at the branching between several geometries has been studied with special attention. These computations have been compared with short shots and pressure measurements in a four rectangular cavities tool and in a box shaped cavity tool. Experimental and theoretical results are in good agreement. |
