Polarity reversal is one of the most frequent installation errors in hot runner systems, yet it is also one of the most avoidable. Despite its simple cause, reversed thermocouple wiring leads to severe overheating, component damage, and production downtime.
Thermocouples generate temperature-dependent voltage based on correct positive and negative wiring. Reversing the two wires inverts the signal, causing the controller to detect extremely low or negative temperatures. In response, the controller delivers maximum power, leading to dangerous overheating.
Limited space, tight wiring channels, and time pressure during mold assembly increase the likelihood of reversed connections. Technicians often work quickly during sensor replacement or maintenance, leading to careless mistakes.
Inconsistent color coding across different regions and manufacturers adds confusion. Some thermocouples lack clear marking, making identification difficult. Without proper labeling, even experienced workers may connect wires incorrectly.
The consequences are serious: overheated heaters, burned nozzles, material leakage, and degraded plastic. Modern controllers often include polarity protection alarms, but older or basic systems may lack this function, allowing damage to occur before detection.
Standardizing wiring procedures, using clearly marked connectors, and double-checking connections can nearly eliminate polarity errors. Simple preventive steps save significant costs and reduce unplanned production interruptions.
