Research On Modeling Of Injection Molding Based On Part Quality

Quality of injection molded part is strongly dependent on the operation of the key processes, among which the filling and the packing are two most important stages. Modeling methods for the filling and packing stages based on part quality are studied in this project. Relation of part quality with injection speed is first discussed. Filling with a constant melt front rate is studied to produce quality parts. Two strategies using secondary variables such as melt-flow-length and melt-front-area are proposed for the implementation of the constant melt front rate. How the melt flow develops in mold cavity is of great importance to part quality. To overcome the invisible status of mold filling, a capacitive transducer based on the polymer dielectric property is proposed and developed to measure the average-flow-length of the polymer melt during filling stage. Experiments are conducted with different mold geometry, different injection velocity profiles and different materials. The experimental results demonstrate the good performance of the capacitive transducer technology. For the injection molding process without installation of the capacitive transducer, a soft-sensor strategy of the melt-front-area using other online measurable variables is proposed. Based on simulation data obtained from molds with different basic geometry, a combined neural network model is developed for the average-flow- Length. Verification results demonstrate that the developed model can apply to molds with different and complex shapes. ii ABSTRACT To develop the quality model of the packing stage, the primary variable, part quality, is correlated with a secondary variable, cavity pressure, which is further correlated to a third online measurable variable, packing pressure. The optimal method to set the packing profile is consequently obtained.