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.
Signal Drift Compensation
Meaning
Automated adjustment of the sensor zero point between moulding cycles eliminates the cumulative effect of sensor signal decay. Implementing signal drift compensation is necessary for piezoelectric sensors which naturally lose charge over time under continuous temperature and pressure. This correction ensures that each cycle starts from the same pressure baseline.
Electronic Calibration
Piezoelectric sensors cannot hold a static charge indefinitely. As the sensor loses charge, the zero-point voltage drifts downwards. Automated signal drift compensation resets the amplifier to zero volts when the mould is open.
Process Stabilization
Without this reset, the process controller would receive an increasingly inaccurate pressure signal as the run progresses. If the signal drifts downward, the machine will continue to inject material past the desired switchover point, causing part flashing or tool damage. Implementing compensation ensures that the switchover occurs at the correct pressure, maintaining consistent part weight and dimensions.
Algorithm Execution
Controllers measure the sensor signal during the cooling phase, when the mould is open and empty. This measured value is then used as the offset for the next cycle, resetting the pressure curve to zero. By continuously recalculating this offset, the system can adapt to changes in ambient temperature and sensor age without operator intervention.