Structural Optimization of a Dual-Sensing Module for Temperature and Pressure Measurement in Injection Mold Cavity
This paper presents the design and optimization of a temperature-pressure sensing module that is structurally integrated into an injection mold. The sensor extracts energy from the polymer melt pressure differential during the injection molding process and uses ultrasonic pulses as the wireless information transmission carrier. The dimension of the piezo ceramic rings that scavenge energy from the mold pressure change is optimized to minimize the volume of the sensor while maintaining the minimum Signal-to-Noise Ratio (SNR) required for reliable signal reception. An analytical expression of the optimal dimension is presented. Based on the optimized design, the sensor module package, together with the injection mold steel and the polymer melt that flows over the sensor into the mold cavity, was modeled using the finite element method. To quantify the behavior of polymer melt and its effect on sensors output, a coupled fluid-structure interaction analysis was performed to examine the mold-melt interface, by using the solution-looping and mesh-morphing techniques. A case study of the sensor design for a 40 mm thick injection mold was investigated by using the presented optimization method and FEA model. Results show that the volume of the piezo stack can be reduced to 0.7 cm3 while meeting the minimum SNR requirement. The minimum insulator thickness of 1 mm is presented by the FEA model to maintain the thermal induced error below 0.5%.