Plastic injection molding workshops often face high humidity, oil mist and volatile plastic gas pollution, which form a harsh working environment for precision electronic components such as hot runner thermocouples. High humidity is one of the main invisible factors accelerating thermocouple aging, insulation failure and signal disorder, yet it is rarely included in daily mold maintenance management. Long-term operation in high humidity environment will gradually damage the structural performance and electrical stability of thermocouples, inducing a series of hot runner temperature control faults.
High humidity penetrates into the thermocouple lead insulation layer and internal sensing wire gap, reducing insulation resistance and causing weak leakage and signal drift. In severe cases, moisture condensation at the wiring terminal will lead to short circuit between positive and negative poles, triggering sudden temperature runaway and controller alarm. The metal probe of thermocouple is prone to oxidation and rust in humid and high-temperature mixed environment, forming a thick oxide layer on the surface, which hinders heat conduction, reduces temperature measurement accuracy and delays response speed.
Workshop oil mist will adhere to the surface of thermocouple probes and leads, carbonize after long-term high-temperature baking, form insulating dirt, affect heat conduction efficiency and cause persistent temperature deviation. Volatile corrosive gas generated by melting modified plastics mixes with humid air, accelerating chemical corrosion of thermocouple alloy probes, resulting in perforation, internal wire breakage and permanent failure in advance. Molds placed idle in high humidity workshop for a long time are more likely to cause thermocouple moisture damage, and direct startup after placement will easily lead to abnormal temperature control.
To avoid humidity damage, enterprises should keep the workshop well ventilated and dehumidified, regularly clean oil mist and dust on thermocouple wiring positions, and adopt sealed fully enclosed thermocouples for molds working in high humidity and corrosive gas environment. When the mold is idle for a long time, it should be sealed and moisture-proof, and preheated and inspected before restarting production. Selecting high-temperature and moisture-proof insulated thermocouple leads can effectively isolate humid air and oil mist erosion, prolong service life, and maintain long-term stable signal transmission and temperature measurement accuracy of hot runner temperature control system.
