In-Situ Evaluation of a Piezoelectric Energy Extraction Device for Wireless Cavity Pressure Sensing in Injection Molding

This paper presents the design, analysis, and validation of a self-energized piezoelectric pressure sensor that extracts energy from the pressure differential of the polymer melt during the injection molding process. To enable a selfenergized sensor design, an analytical study has been conducted to establish a quantitative relationship between the polymer melt pressure and the energy that can be extracted through the use of a piezoelectric converter. Temperature and pressure are monitored during an injection molding cycle and the performance of the piezoelectric element is evaluated with respect to a mechanically static, electrically transient model. In addition to corroboration of the proposed model, valuable statistical information about the working temperature in the prototype sensor will prove very useful in the package design of molding cavity sensors. A linear model examining the energy conversion mechanism due to interactions between the mechanical strain and the electric field developed within the piezoelectric device is established. This model is compared to the functional prototype design to evaluate the relevance of the assumptions and accuracy. The presented design enables a new generation of self-energized sensors that can be employed for the condition monitoring of a wide range of