Non-destructive measurement of cavity pressure during injection molding process based on ultrasonic technology and Gaussian process

Abstract

Non-destructive measurement of the cavity pressure is of great importance for monitoring, optimizing and controlling the injection molding process. However, to date, almost all researches have relied on embedded pressure probes, and holes have to be drilled in the molds. In this paper, a non-destructive cavity pressure measurement method is proposed based on ultrasonic technology and a Gaussian process. According to the pressure-volume-temperature profile, the cavity pressure of a given polymer can be treated as a function of the density and the temperature. Moreover, the cavity pressure is significantly affected by injection hydro-cylinder pressure. Ultrasonic technology is employed to detect the variation of polymer density during injection molding. The Gaussian process is adopted to model the functional relationships between the cavity pressure, the ultrasonic signal, the mold temperature and the injection hydro-cylinder pressure. Experimental results show that the proposed Gaussian process regression model has a better modeling performance than that of the neural network regression model, and the proposed measurement method is capable of measuring the cavity pressure at different processing conditions and measurement locations during injection molding. In general, the proposed method offers several advantages: (1) non-destructive, (2) flexible, (3) no wires, (4) low-cost, and (5) health and safety, so it has great application prospects in injection molding.