Thickness sensor for injection moulding

TRE Measurement and Kaman Sensors have developed a sensor that measures the thickness of plastic as it is being moulded. It can also measure the gap between the mould and the core during set-up to ensure proper position.

With this sensor, a plastics manufacturer can obtain information on the movement of the mould core as the plastic is being injected. This information can be used to adjust parameters affecting core movement (melt temperature and core/mould temperature) and for SPC monitoring.

Kaman’s sensor is embedded and sealed into the outer mould. The face of the senor is typically flush with the inside wall of the outer mould, so that little or no marking occurs on the product being moulded. The sensor is usually positioned towards the bottom of the mould, where the core is least supported and thus most dimensionally unstable.

The inductive sensors can look through the gap between the core and the mould, and through the plastic to determine the position of the copper or iron inner core. Kaman’s inductive technology is unaffected by the presence of plastic.

Even though the sensor is installed in a cooled environment (the mould), it can withstand temperatures exceeding 200 °C and pressure up to 20,000 psi.