Ultrasonic monitoring and control in plastic manufacturing

In the search for a simple, robust and noninvasive measurement, the use of sound is explored to monitor polymer processing. A new pulsed ultrasonic measurement is developed based on the absorption of ultrasonic energy (AUE) from the plastic. The signal proves to be computationally efficient, robust and simple to use. The sensitivity of the signal is demonstrated in an injection molding process.; The AUE signal led to the investigation of continuous sound waves. Different configurations are surveyed. One such configuration is formed by placing a piezoelectric element normal to the cavity face. In this arrangement, standing waves within the mold develop. When tuned to the appropriate frequency; the waves constructively interfere, producing a mechanical resonance within the mold. This configuration is termed Ultrasonic Resonance Monitoring (URM). Plastic presence at the mold face is shown to change the URM signal.; Definitions and terms are proposed to explain the concepts and components necessary to realize a URM system. The design of a URM transducer used to monitor the plastic state within the cavity of an injection molding process is presented. An experiment is conducted to study the effects of the plastic on the transducer. Changes in the injection molding parameters are shown to modify the URM profile.; In an effort to explain and understand the URM signal, a continuous wave acoustic model is used to identify influential physical parameters. An experiment is conducted to measure the acoustic properties of the plastic during molding. Throughout the molding process, pulsed ultrasonic waveforms are collected while simultaneously measuring the impedance of the URM transducer. The acoustic 3 properties are extracted from the waveforms and used in the model to simulate the response of the URM transducer.; Two examples are presented to show how the signal may be used to monitor and control the injection molding process. The first example predicts part weight using features found in the URM profile. The second example uses the URM signal as the transfer indicator in one-step transfer control. The URM based transfer is compared against ram position and cavity pressure transfer and is shown to mold parts with the smallest deviation of part weight.