Large-scale auto parts and household appliance molding workshops equipped with numerous high-power servo injection machines, frequency converters and high-current hydraulic control cabinets are filled with complex superimposed alternating electromagnetic field, seriously disturbing weak millivolt signal of ordinary single-shielded hot runner thermocouple; double-layer braided full-shield thermocouple gradually becomes standard matching accessory for Synventive valve gate and high-end domestic multi-zone hot runner to solve electromagnetic interference troubles thoroughly. Double-shield structure consists of inner metal braided shielding layer wrapping core thermo-alloy wire and outer second shielding layer coated outside intermediate insulation, dual isolation layers block external alternating magnetic field and stray electric field from penetrating into internal measuring wire from radial direction, which single-layer shielded products cannot achieve under severe electromagnetic pollution environment.
Standard wiring specification requires outer shielding layer to suspend without grounding and only inner shielding layer to implement single-point grounding near controller terminal, this unique grounding design effectively avoids ground loop interference risk easily triggered by double-layer simultaneous grounding. In dense wiring area of 32-cavity and above multi-cavity hot runner where dozens of heating coils and solenoid valves gather together, stray electromagnetic noise is strongest; single-shield thermocouple often appears over 10℃ random temperature jump on controller screen, while double-shield finished wire can restrict fluctuation within ±0.8℃ to satisfy precision forming requirement of medical transparent plastic and high-gloss automotive exterior components.
Outer insulation of double-shield thermocouple mostly adopts high-temperature Teflon composite material with excellent oil-proof and acid-resistant performance, adapting severe workshop environment mixed with hydraulic oil mist and plastic corrosive volatile gas around injection equipment. Though unit production cost of double-shield specification is roughly 30% higher than conventional single-shield thermocouple, its stable signal greatly reduces abnormal heating fault caused by interference and avoids frequent unplanned production halt loss.
Electromagnetic pollution level of workshop rises year by year with continuous popularization of full-servo high-speed injection molding equipment; more and more export-oriented mold factories matching Husky original hot runner upgrade all supporting thermocouple to double-shield specification during regular equipment overhaul. Long-term cost accounting proves double-shield thermocouple's comprehensive life-cycle cost is far lower than repeatedly replaced cheap single-shield alternatives in strong electromagnetic field workshop.
