External heating band wrapped around hot runner manifold and nozzle works under large alternating AC current during continuous production of YUDO and domestic multi-cavity commodity hot runner, generating strong alternating magnetic field all around heating component; casual random clamping and close fitting of thermocouple signal cable against heating band outer surface easily produces inductive coupling interference and continuous measurement deviation, which ranks among frequent on-site wiring defects leading to unstable closed-loop temperature regulation. Thermocouple captures faint millivolt-level Seebeck potential determined by hot runner actual temperature, and such weak signal is extremely susceptible to external alternating magnetic flux cutting effect. When unshielded or single-shield thermocouple wire is fixed within 3cm range of high-power heating band, alternating magnetic field induced by periodic current fluctuation constantly cuts internal core conductors and generates unexpected parasitic alternating voltage superimposed on effective measuring signal, finally causing irregular floating reading that cannot match real hot runner temperature. In many practical maintenance cases, operators find temperature display jumps up and down randomly by 10℃ to 30℃ without any regular rule, and they repeatedly replace intact thermocouple before discovering unreasonable wiring layout beside heating bands, resulting in unnecessary spare part waste and delayed production debugging progress.
Standard construction specification clearly defines safety separation distance requirement: all thermocouple wiring harness must maintain no less than 5cm clearance from heating band and its power lead wire, adopting high-temperature resistant plastic wire clip to fix signal cable along mold frame edge away from heating source area. If mold internal layout space is extremely compact to satisfy specified spacing, wrap whole thermocouple outer cable with independent seamless metal shielding sleeve for supplementary anti-interference protection, and connect auxiliary shielding layer single-point grounding at control cabinet side following standardized grounding rule. Quarterly regular equipment maintenance comprehensively sorts out disordered wiring left by previous emergency maintenance, rectifies over-close clamping hidden trouble channel by channel and records rectification information into equipment maintenance archive. After wiring rectification completion, carry out continuous 24-hour stable temperature tracking test to verify interference elimination effect, accumulating field data to optimize subsequent new mold wiring construction standard and lower inductive interference failure occurrence rate year by year.
