Piezoelectric Cavity Pressure Sensor Setup in Micro Injection Moulding
Direct piezoelectric cavity pressure sensing in micro injection moulding requires sub-micron bore tolerances, rigid preloading, and active thermal drift compensation.
Preload Sleeve Torque
Meaning
Tightening moment applied to the threaded retention sleeve of a cavity pressure sensor establishes the necessary compressive force on the transducer. Applying the correct preload sleeve torque ensures that the sensor remains seated and produces a linear voltage signal. This parameter is specified by the sensor manufacturer and varies with the thread size and sensor type.
Mechanical Tension
Squeezing the transducer against the bottom of the pocket prevents movement. When the preload sleeve torque is too low, the sensor can shift, introducing measurement errors. This torque is applied using a calibrated torque wrench.
Signal Stability
Over-tightening the sleeve can damage the delicate piezoelectric crystal or cause a large baseline signal offset. If the preload sleeve torque exceeds the maximum limits, the sensor may experience thermal shock or signal saturation during the injection cycle. Maintaining the correct torque prevents signal drift and ensures consistent part-to-part quality over thousands of cycles.
Installation Practice
Toolmakers must clean the sensor pocket and threads before installation to ensure that friction does not corrupt the torque reading. Contaminants such as resin residue or metal shavings can lead to an artificially high preload sleeve torque, meaning the actual force on the sensor is insufficient. Routine checks of the torque during preventative maintenance cycles help prevent sensor failure and reduce production downtime.