What Are the Maintenance Cycle Standards for Hot Runner Thermocouples

Developing a systematic maintenance and replacement cycle for hot runner thermocouples is a significant way to stabilise injection moulding quality and minimise unscheduled shutdowns. The service life and maintenance cycle of the moulding material temperature, production cycle frequency, mould structure and thermocouple grade can be classified into conventional standard cycle and high-load accelerated cycle.

For the conventional working conditions, such as PP, ABS and ordinary household appliance plastics with the moulding temperature below 280°C and medium daily production volume, the regular inspection cycle of thermocouples is every three months and calibration and comprehensive ageing inspection is every six months. The whole replacement cycle is 12 to 18 months," The working conditions are such that the temperature fluctuation is small, the corrosion is weak, and the thermocouple can maintain stable performance for a long time.

For high temperature technical polymers such as PPS, LCP, PEEK and glass fibre reinforced materials with long-term operating temperature exceeding 320°C, the ageing speed of thermocouples is greatly enhanced. The inspection cycle should be decreased to 1-2 months, and the replacement cycle is managed between 6-10 months. High temperature and fibre wear will cause sheath attenuation and signal drift readily, and need replace periodically more often.

High-cycle continuous production moulds, such as packing caps and thin-wall containers that run 24 hours a day, suffer from major problems of mechanical vibration and heat stress. Even if the temperature is moderate, the service life will be reduced. It is recommended to check every month and change sensitive thermocouples every 8 to 12 months.

In addition to preset cycles, real-time status judgement should be integrated. The thermocouple must be changed promptly, including temperature drift, poor response, occasional signal jump, and frequent open circuit alert. The establishment of equipment spare parts files and the recording of the usage time of each set of mould thermocouples can realise the standardised management, advance the preparation of shutdown maintenance, and avoid the production being forced to stop due to the sudden failure of thermocouples.