Heat-conducting thermal grease is commonly applied to fill tiny clearance between thermocouple probe outer wall and hot runner mounting hole for improving heat transfer efficiency on Husky and domestic high-precision hot runner, but excessive daub, inferior grease material or wrong grease model selection will trigger multiple hidden risks including local overheating, carbon deposition sticking and insulation failure instead of optimizing measuring accuracy. When maintenance workers fill thermal grease excessively into mounting hole, redundant grease overflows around probe root and spreads to sheath outer surface; under long-term high-temperature baking above 300℃ of hot runner working condition, common low-grade thermal grease gradually decomposes into sticky carbon residue and tightly sticks probe with hole inner wall, making later thermocouple disassembly extremely difficult and easy to bend probe or damage built-in spring during forced pulling-out operation.
Inferior thermal grease containing volatile organic additive releases corrosive acid gas after high-temperature pyrolysis, the corrosive vapor permeates along tiny gap into mineral-insulated thermocouple internal structure and slowly erodes magnesia filler and core alloy wire, leading to gradual insulation resistance decline and intermittent short-circuit fault after several months of continuous production. High-temperature PEEK and PPS special hot runner working above 420℃ must select high-temperature resistant inorganic thermal grease; ordinary silicone-based grease fails to resist ultrahigh heat and quickly liquefies outflow to lose heat conduction effect, meanwhile residual liquid grease pollutes surrounding wiring insulation layer and causes insulation swelling aging.
Standard operation regulation limits thermal grease daub quantity only on probe front 1/3 measuring section and prohibits full-surface smearing; high-temperature working environment uniformly adopts high-temperature sintered type heat conduction filler matching specification. Many small maintenance teams use random cheap universal thermal grease regardless of hot runner actual working temperature to save cost, resulting in early scrapping of matched precision thermocouple. Scientific standardized use of thermal grease can maximize heat conduction advantage and avoid unnecessary component damage loss for hot runner temperature control system.
