Excessive heating current is a common abnormal operating state in hot runner temperature control systems, which will not only affect molding stability, but also cause irreversible damage to matched thermocouples and sharply shorten their service cycle.
When the system outputs overrated large current continuously, the overall ambient temperature of hot runner heating zones rises rapidly and exceeds the normal set range. Thermocouple probes stay in ultra-high temperature environment far beyond rated working standard for a long time. The internal alloy core wires accelerate metal grain transformation, thermal fatigue accumulates rapidly, and the original stable thermoelectric conversion performance declines continuously, leading to earlier and more serious temperature signal drift.
Long-term overcurrent heating also accelerates aging and deterioration of high-temperature insulating fillers inside thermocouples. Excessive heat will gradually soften, shrink and even carbonize insulating materials, destroying internal insulation structure. It is easy to trigger internal partial short circuit, signal disorder and intermittent power leakage faults, and in severe cases, it will directly burn off internal sensing core wires and cause complete scrapping.
Meanwhile, ultra-high ambient temperature intensifies surface oxidation and corrosion speed of thermocouple probes. The anti-oxidation protective coating fails rapidly, and the probe metal body is prone to rust and deformation. Under combined action of high temperature and plastic volatile gas, the wear resistance and corrosion resistance drop sharply.
Besides direct performance damage, frequent overcurrent heating leads to sharp temperature rise and fall fluctuation, making thermocouples bear stronger cold and heat alternating impact. All these factors jointly accelerate overall aging progress. Operators shall strictly set reasonable heating power parameters, timely check aging heating rings that cause current surge, keep current within standard working range, and reduce extra high-temperature load of thermocouples effectively.
