Ultrasound based monitoring of the injection moulding process - methods, applications and limitations.
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Proceedings of the Polymer Processing Society, 29th Annual Meeting (PPS-29), July 15-19, 2013, Nuremberg (Germany)
We developed novel non-invasive ultrasound based systems for the measurement of temperature
distributions in the screw-ante chamber, the detection of unmelted granules and for the monitoring of the plasticizing
process along the screw channel. The temperature of the polymer melt stored in the screw ante-chamber after the
plasticization should be homogeneous. However, in reality the polymer melt in the screw ante-chamber is not
homogeneous. Due to the fact the sound velocity in a polymer melt is temperature depending, we developed a
tomography system using the measured transit times of ultrasonic pulses along different sound paths for calculating the
temperature distribution in radial direction of a polymer melt in the screw ante-chamber of an injection moulding
machine. For the detection of unmelted granules in the polymer melt we implemented an ultrasound transmission
measurement. By analyzing the attenuation of the received pulses it is possible to detect unwanted inclusions. For the
monitoring of the plasticizing process in the channels of the screw an ultrasonic pulse is transmitted into the barrel. By
analyzing the reflected pulses it is possible to estimate solid bed and melt regions in the screw channel. The proposed
systems were tested for accuracy and validity by simulations and test measurements.