Over the last decade, there has been an increased drive in the polymer industry & polymer research toward the development of non-invasive monitoring techniques for injection moulding. 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 complex thermal history of the polymer during the plasticizing in the channel of the screw. Due to the fact the sound velocity in a polymer melt is temperature depending, we developed a tomography system [1] 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 transit time and the attenuation of the received pulse it is possible to detect unwanted inclusions during the injection of the polymer melt into the mould. For the determination of the solid bed - melt pool ratio in the channel of the plasticizing screw an ultrasonic pulse is transmitted into the barrel and reflected due to the acoustic boundaries (barrel/polymer/screw flight or screw root) during the plasticizing process. By automated analysis of the reflected pulses - measured at different positions of the screw - it is possible to monitor the melting process online (in opposition to the time-consuming ‘screw pulling-out’ method). The proposed systems were tested for accuracy and validity by simulations and measurements. [1] B. Praher et al., "A Novel Ultrasound-Based System for Temperature Distribution Measurements in Injection Moulding", Proceedings 'The 13th Mechatronics Forum International Conference', Vol. 1/3, Trauner Verlag, Linz/Austria, Page 213-220, 9-2012