Standardized regular maintenance is the most economical method to prolong hot runner thermocouple service life. Industry mature maintenance cycles divide into per-shift daily inspection, 50,000-cycle intermediate maintenance, and 200,000-cycle thorough overhaul.
Per-Shift Daily Inspection. Operators check thermocouple outer wire appearance for extrusion scratches, high-temperature scorch cracks, and plastic volatile gas corrosion damage near the mold clamping position. Simultaneously observe controller temperature reading fluctuation amplitude. If data jumps irregularly or shows obvious deviation from set value, preliminary troubleshoot loose contact or shielding wire damage immediately before continuous production.
50,000-Cycle Intermediate Maintenance. Dismantle bayonet fixed thermocouples from nozzle/manifold reserved holes. Inspect built-in spring elastic fatigue status and probe end oxide layer accumulation. Polish oxide dirt on probe measuring surface with fine abrasive cloth to recover accurate heat conduction contact. Replace permanently deformed fatigue springs with same-specification spare accessories. Carry out accuracy calibration via standard high-precision temperature calibrator. Compensate controller temperature offset coefficient for thermocouples with slight measurement drift. Scrap and replace sensors whose error exceeds ±1.5°C full range. Rearrange messy wiring inside mold wiring groove and fix loose wire binding clips.
200,000-Cycle Thorough Overhaul. Partially disassemble hot runner manifold and nozzle components for full thermocouple systematic inspection. Pull out all embedded manifold thermocouples to check armored sheath cracks and inner alloy wire oxidation status. Replace severely corroded or internally broken thermocouples in batch. Test insulation resistance between thermocouple core wire and outer sheath with a megohmmeter-qualified insulation value shall be above 1 MΩ. Unqualified products must be eliminated immediately to avoid short-circuit damage to the hot runner temperature controller. Clean residual carbonized plastic dirt around thermocouple installation holes to guarantee good heat conduction between probe and measured hot runner metal surface.
Additional Operating Specifications. When heating up the hot runner system from a cold state, strictly follow a segmented temperature rising curve instead of one-time rapid overheating to reduce instantaneous thermal shock damage to the thermocouple probe. Avoid strong pulling of thermocouple outer wires during mold assembly and disassembly to prevent internal alloy wire hidden fracture. Following these standardized maintenance operations can increase average thermocouple service life from 6–8 months to over 14 months.
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