Thermal conductive grease is used to fill tiny clearance between probe outer wall and hot runner mounting hole for improving heat transfer efficiency on Husky and YUDO precision hot runner, while excessive smearing dosage, mismatched temperature-resistant grade and inferior grease selection will produce carbon deposition, insulation corrosion and measuring lag damage instead of optimizing heat conduction effect. Standard operation only daub high-temperature resistant grease on front one-third measuring section of probe surface; redundant overflow grease spreads along sheath root under long-term over 300℃ high-temperature baking, organic constituent volatilizes gradually and leftover inorganic residue solidifies into hard carbon scale tightly bonding probe and mounting hole inner wall together, bringing huge difficulty for later maintenance disassembly and easily bending probe irreversibly during forced extraction operation.
Using low-temperature silicone-based ordinary grease on PEEK ultrahigh-temperature hot runner over 420℃ will lead grease rapid liquefaction and flow away within short time, losing heat conduction function meanwhile leaked grease soaks surrounding wire insulation layer and causes plastic coating swelling deterioration. Inferior cheap thermal grease contains unstable acidic additive which decomposes corrosive gas after high-temperature pyrolysis, gas permeates sheath micro crack into internal magnesia insulation layer and erodes core alloy wire slowly to reduce insulation resistance progressively and form cumulative measuring drift.
Workshop compiles graded grease selection guide according to hot runner peak working temperature: below 300℃ adopt medium-temperature silicone thermal grease, 300~420℃ select inorganic composite high-temperature grease, above 420℃ configure fully inorganic ultrahigh-temperature resistant dry conductive paste without organic component. Weekly maintenance inspects probe surrounding carbon deposition condition during routine patrol, clear aged solidified grease residue timely and refill matched grade grease in standard dosage to guarantee long-term stable heat transfer efficiency of installed thermocouple.
