Based on the previous focus on thermocouple temperature control and component maintenance in hot runner injection molding, typical scenarios of reversed polarity of the hot runner temperature sensor wire (thermocouple) are as follows:
Temperature Reading Reverse Drift: When the hot runner heats up, the temperature value displayed by the temperature controller continues to decrease, completely deviating from the actual temperature change trend.
Reading Deviation with Small Temperature Differences: When the actual temperature of the hot runner is close to the ambient temperature, only a few degrees Celsius deviation occurs, which is difficult to detect directly and can lead to long-term, hidden temperature control inaccuracies.
Abnormal Signal Jumps: Under some reversed connection conditions, the temperature reading jumps irregularly and slightly, which will not directly trigger an open circuit alarm and is easily misjudged as a thermocouple aging fault.
Heating Logic Disorder: The temperature control system receives a reverse signal and continuously triggers incorrect heating commands, ultimately causing the actual temperature of the hot runner to far exceed the set value, leading to production failures such as plastic decomposition and product edge scorching.
When the above typical symptoms appear, first check the positive and negative terminals of the temperature sensing wire; there is no need to replace the thermocouple directly.
