Temperature measurements in the depth and at the surface of injected thermoplastic parts

This work describes a novel experimental set-up which allows the measurement of the temperature field in the depth of injection moldings throughout the length of injection molding cycles and after ejection as well. An experimental device has been designed and realized, including a specific mold equipped with a tubular needle for guiding an embedded micro-thermocouple inside the cavity. Disturbance caused by the probe remains weak and under control. Temperature field modeling has been performed using Moldflow and Cat1D softwares. Cat1D is a thermal modeler developed at the OPERP laboratory. Measured depth temperature history slope coincides satisfactorily with the Cat1D computed one. Surface temperature measurements reveal some thermal singularities corresponding to modifications in the thermal boundary conditions during injection cycle phase changes. These temperature field evolution singularities, confirmed by Cat1D modeler, are due to the TRC phenomenon within the cavity and to the ejection point. The quantitative assessment of these phenomenon impacts appears essential to control injection molded part dimensions.