Injection molding process monitoring using a self-energized dual-parameter sensor

On-line monitoring of polymer melt state is critical to ensuring part quality in injection molding. This paper presents a novel, dual-parameter sensing method for simultaneous measurement of pressure and temperature variations within the mold cavity through a modulator circuit. Pressure variation during the molding cycle, which is proportional to the electrical charge output of a piezoceramic stack, is discretized into acoustic pulses that are subsequently frequency-modulated by a temperature-sensitive oscillator (TSO). The ability to measure two parameters using one sensor package without batteries and cables for data transmission provides a new platform for monitoring injection molding processes.