Reasons for Abnormal Over-temperature Alarm of Hot Runner Thermocouples

A typical protective flaw in hot runner temperature control systems is the sudden over-temperature warning, which will cause heating to cease and impede output. The thermocouple itself and external matching circumstances are the main culprits.

Thermocouple displacement and incorrect contact come first. A false over-temperature warning is set off when the probe moves away from the predetermined measuring position and immediately approaches the heating elements, gathering a much higher local heat source temperature rather than the typical runner temperature.

Heat buildup and significant carbon deposition on the probe come in second. The detecting head is covered in thick layers of carbon, which causes heat to collect and dissipate slowly. False alarms are common because the detected temperature is consistently greater than the actual normal temperature.

The third is a thermocouple's internal short circuit. Positive and negative wires come into contact with one another due to damaged internal insulation, which disrupts signal output and causes the controller to misread ultrahigh temperature data.

Unreasonable controller parameter setting comes in fourth. Even at normal operating temperatures, alarms can be easily triggered by an excessively low over-temperature protection threshold and incorrect temperature zone matching settings.

The fifth is an uncontrollably high heating ring temperature. The thermocouple accurately transmits back the high temperature to initiate the regular protection warning when damaged heating rings are unable to stop heating properly, resulting in actual overheating.

When an alert goes off, use an infrared temperature sensor to determine whether it is a false warning or a real overheating. To completely eradicate alarm failures and restore regular heating operation, clean carbon deposits, reposition the installation, check for internal line short circuits, and optimize protective parameters one by one.