Infrared temperature measurement in thermoforming

Paul Boughton

The process of thermoforming a plastic sheet depends critically upon temperature, says pyrometer manufacturer Calex Electronics. 

Forming temperatures typically range from 120°C to 370°C. Precise temperature control is required, and the company’s PyroMini infrared temperature sensor is ideal.

The plastic sheet is heated by infrared heaters; a temperature sensor is used for each heating zone to ensure it is heated evenly. For the best control, at least 10 points should be measured: all four corners and the centre, on the top and bottom surfaces.

The sensing head is positioned between the heating elements. High ambient temperatures mean that PyroMini JA (up to 120°C ambient) and HA (up to 180°C ambient) models are most suitable. No cooling is required for the sensing head.


The production rate is often limited by the cooling time. The PyroMini monitors the surface temperature of the formed part as it is cooled with an instantaneous 240ms response time, so the operator or control system can see immediately when the part is cool enough and remove it quickly.

The optional touch screen display provides a large, bright indication of measured temperature, two alarm relay outputs, and data logging to a MicroSD Card. The sensor is fully configurable via the touch screen.

For connection to a PLC or temperature controller, two output types are available: 4-20 mA or RS485 Modbus.

Calex can also provide other thermoforming temperature systems ranging from a single sensor with a PID controller, to a digital network of hundreds of sensors, with display, control, alarm, analogue output and data acquisition functions.

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