All complete hot runner systems assembled by brand manufacturers undergo standardized multi-stage thermocouple testing before mold delivery to eliminate dimensional mismatch, signal abnormality and hidden structural defects, forming a complete quality inspection traceability system covering raw material testing, offline probe calibration, mold assembly wiring test and high-temperature aging simulation. The first testing stage is raw material incoming inspection for thermocouple components, executed before probe assembly. Laboratory inspectors verify alloy wire purity, sheath material composition and insulation heat resistance, conducting IEC 60584 thermoelectric curve testing to confirm J/K-type tolerance grade meets customer requirements: Grade 1 for medical/automotive molds and Grade 2 for packaging molds. Corrosion-resistant alloy sheaths additionally pass acid immersion anti-corrosion testing, while ultra-miniature micro probes undergo bending fatigue testing to guarantee no internal wire breakage after 500 small-radius bending cycles. Unqualified raw material batches are rejected before production assembly.
The second stage is offline independent probe calibration. Each finished thermocouple is placed in a dry-block temperature calibrator for three-point testing at 200℃, 300℃ and 400℃, recording deviation values against national standard reference sensors. Probes with deviation exceeding the specified tolerance are reworked or scrapped immediately. Extension cables and connector accessories are separately tested for shielding effectiveness: electromagnetic interference simulation equipment generates high-frequency alternating magnetic fields to verify signal fluctuation stays within ±0.5℃ with shielding intact, filtering out unqualified unshielded harnesses prone to signal jitter.
The third stage is on-mold wiring continuity test after thermocouple installation on manifolds and nozzles. Technicians connect all probes to a standard multi-zone controller, conducting cold-state continuity inspection to screen open-circuit, short-circuit and reversed polarity faults. Every mounting screw is retightened with torque-limited screwdrivers according to brand specifications, then the mold is heated to low temperature of 120℃ to observe early-stage abnormal alarms induced by thermal expansion loose contact. Wiring harness routing is checked for sharp mold plate edge friction risks, with wire gaps adjusted to separate signal cables from heater power lines to avoid cross-interference.
The fourth core testing stage is 500-hour high-temperature aging simulation, simulating real continuous production conditions. The hot runner system runs at customer-specified production temperature, with all thermocouple signals recorded automatically every 10 minutes by data logging equipment. Inspectors monitor long-term signal drift, response speed and stability; probes showing gradual deviation over ±1.5℃ during aging are disassembled and replaced. This aging test exposes hidden defects including internal wire micro-fractures, poor sheath sealing and fatigued nozzle springs that only appear after long thermal cycles, which cannot be detected by short-term static calibration.
The final delivery test generates a complete thermocouple quality report including raw material certificates, three-point calibration data, aging test curves and wiring inspection records, attached to the mold delivery document for customer quality audit. For export molds targeting EU and US markets, additional RoHS and LFGB heavy metal precipitation testing reports are appended. Standardized multi-stage pre-delivery testing eliminates over 98% of thermocouple matching and performance faults before molds leave the factory, reducing customer on-site debugging time by over half and avoiding mass production failures caused by uninspected defective sensors.
