Novel three-dimensional in-cavity transient temperature measurements in injection molding and fluid-assisted injection molding

This report presents novel experimental set-ups which allow the measurement of three-dimensional temperature fields in the depths of injection molding cavities throughout molding cycles. Two specific molds equipped with two types of temperature measuring devices, i.e., a mesh type device consisting of thermocouples mounted on metal wires and a tubular type device consisting of tubular needles guiding embedded micro-thermocouples inside the cavities, have been designed and built. Temperature distributions in both injection molding and fluid assisted injection molding processes, including gas and water assisted injection molding, were measured and recorded by a data acquisition system on a personal computer. It was found that the tubular type device induced much less flow disturbance and provided accurate temperature profiles. Among the processes, the water assisted injection molding process required the least time to cool the parts, followed by gas assisted injection molding and conventional injection molding. In addition, the experimental results also suggested that the shear heating by viscous dissipation in the runners leads to a significant increase in melt temperature. A precise measurement of the in-depth temperature profile can be helpful to better understand the molding phenomena, to validate numerical simulation results, as well as to optimize the parameters for the molding processes.