Continuous wave ultrasonic process monitor for polymer processing

Abstract

An injection molding apparatus is disclosed that includes an injection mold, a mold injector, and means for monitoring the injection mold process using acoustic energy. The injection mold includes a cavity for receiving an injection mold material, such as a polymer as injected via the mold injector. The monitoring system includes an acoustic energy generator, an ultrasonic crystal, and an energy monitoring device. The acoustic energy generator produces continuous acoustic energy to be non-invasively applied to the injection mold as the polymer is delivered into the mold. The energy monitoring device monitors changes in dynamic parameters of a resulting continuous resonant frequency established by the acoustic energy generator through the ultrasonic crystal. The ultrasonic crystal serves also as a transducer to receive an output signal from the mold to be delivered to the energy monitoring device. It is this output signal that is processed to determine dynamic parameters that change based on the change of the continuous resonant frequency. This change of dynamic parameters can identify at least one characteristic of the polymer such that refined control of the injection process may be achieved by monitoring such characteristics through the continuous wave resonant frequency monitoring approach applied by the monitoring system.