Meaning
Quartz-based sensor technologies convert mechanical pressure into measurable electric charges within the mould cavity. A piezoelectric force transducer positioned behind an ejector pin or directly in the cavity wall registers changes in pressure during the injection cycle. This real-time signal allows the moulding machine to monitor and control the cavity pressure dynamically.
Charge Generation
Pressure applied to the quartz crystal causes a displacement of ions within the crystal lattice, generating a proportional electric charge. This charge is transmitted via a shielded cable to a charge amplifier where it is converted into a voltage signal. Because quartz is highly stable under temperature changes, the sensor remains accurate even in hot moulds.
Unlike strain-gauge sensors, the quartz crystal exhibits almost zero deflection under load, which ensures that the measurement does not interfere with the mechanical operation of the mould.
Cavity Pressure
Packing pressure and volumetric fill are the primary drivers of part quality in injection moulding. The piezoelectric force transducer measures these pressures directly, providing a fingerprint of the moulding cycle. This fingerprint helps to detect short shots, flash, and part weight variation before the mould opens.
Process Optimization
Automatic rejection systems use the pressure curve to sort out-of-specification parts during the production run. If the peak pressure falls below a set limit, the machine diverts the current shot to the scrap bin. This automated control reduces the need for manual inspection of every part.
