High-frequency ultrasonic oscillation cleaning is widely adopted to eliminate stubborn carbon residue inside runner channel of Husky and domestic multi-cavity packaging hot runner molds; unprotected operation, excessive output power and overlong cleaning duration transmit continuous fatigue vibration to nearby embedded fixed thermocouple and gradually loosen internal compact magnesia insulation filling structure. High-frequency mechanical vibration propagates through cleaning liquid and mold steel matrix to thermocouple metal sheath, repeated alternating fatigue shock makes originally dense magnesia powder generate tiny intergranular gaps inside insulation layer after multiple cleaning cycles. After cleaning procedure finishes and mold returns to formal production, damp cleaning solution vapor and floating workshop corrosive gas penetrate inward along formed gaps, eroding internal core thermo-alloy wire under subsequent hot runner high-temperature heating environment and triggering progressive insulation resistance decline and irregular measuring drift.
High-concentration alkaline cleaning solvent used for ultrasonic bath easily permeates into sheath micro-cracks formed by long-time vibration fatigue; residual alkaline liquid stays inside insulation layer after incomplete drying, continuously corroding core wire and accelerating premature hidden failure which cannot be found during post-cleaning initial trial run but breaks down within one to two months of mass production. Many maintenance operators blindly raise ultrasonic power and extend cleaning time to improve carbon removal efficiency and save working hours, ignoring pre-protection wrapping regulation and resulting in centralized batch thermocouple hidden damage after mold overhaul cleaning.
Formal pre-cleaning operation standard divides thermocouple into two classification protection modes: detachable bayonet type must be completely disassembled and stored inside sealed dry anti-corrosion storage box before cleaning construction; non-detachable embedded fixed thermocouple needs full wrapping with thick waterproof high-temperature Teflon cloth and fixed with high-temperature resistant binding band to isolate cleaning liquid infiltration and ultrasonic oscillation impact thoroughly. After mold cleaning is finished and placed in ventilation environment for full natural drying for more than 24 hours, maintenance staff implement one-by-one insulation resistance testing for all previously protected thermocouple to screen potential hidden damaged products timely before mold reassembly and production startup. Workshop compiles ultrasonic cleaning operation guide with clear thermocouple protection clauses posted beside cleaning equipment to standardize daily maintenance operation flow effectively.
