Design and validation of a self-regulating melt valve for injection molding, 2004--2005

The objective of the research was to establish the technical feasibility of providing gate-level control of flow rate and pressure in injection molding, with no increase in cost compared to hot runner valve-gated systems. The self-regulating valve designed to achieve this goal works on the key principle of controlling melt flow by regulating the amount of pressure drop in the melt channel. The new design operates on the principle of balanced forces which greatly reduces the actuation force required to regulate the juncture area and consecutively controls the volumetric output with an ease of operation. The design has been validated by the series of experiments characterizing the performance of the valve to control the melt flow at a given pressure drop as a function of machine parameters and material properties.; The ability to control the melt pressure at each valve to bring about changes in part quality was demonstrated. The valve was operated in open loop mode (without feedback from the melt pressure transducers) and closed loop mode (with feedback from the melt pressure transducers). It was shown that the consistency of the molding process is significantly improved (by a factor of two or more) compared to conventional injection molding, though closed loop control could be improved with faster servovalves. The self-regulating valves were also shown to provide the flexibility to precisely tune two cavities in a family mold, and also reduce the clamp tonnage by 50% by offsetting the pressure profiles by two seconds. It is strongly believed that the valve designs will have extensive applications in injection molding, extrusion, and blow molding.