Standard ring, spring and button head thermocouples cannot adapt to special-structure hot runner products, and customized thermocouple design is required according to manifold structure, nozzle size, molding material and mold space constraints, covering micro miniature, high-pressure resistant, corrosion-resistant, ultra-long and bent special-shaped sensing probes. Micro mini hot runners are widely used in 64-cavity and 128-cavity electronic connector thin-wall molds, with nozzle tip diameters less than 2mm and extremely narrow installation reserved holes. Conventional 1.5mm spring probes cannot be installed, so manufacturers customize 0.6–1.0mm ultra-thin button head J-type thermocouples with flat low-profile sensing ends, matched with ultra-fine shielded extension cables to avoid wiring occupation of mold cavity layout. The internal spring structure is canceled, and high-temperature thermal conductive grease is filled at the contact position to ensure stable heat transfer without air gap deviation.
High-pressure resistant customized thermocouples target large automotive bumper, instrument panel and large household appliance shell valve gate hot runners. During injection, the melt pressure at the nozzle gate can exceed 1200bar, and standard armored probes are prone to deformation and loose contact under long-term high-pressure impact. Customized products adopt thickened 1.2mm Inconel sheath walls, with integral stamping forming at the sensing head without welding seams, resisting melt impact and high-temperature creep deformation. For hydraulic valve stems that reciprocate frequently, offset bent thermocouple probes are customized to avoid collision between the sensing head and the valve needle, and the bending angle can be adjusted according to the actual internal space of the nozzle.
Corrosion-resistant customized thermocouples are exclusive for molding PVC, flame-retardant plastics, fluoroplastics and recycled materials. Such materials release corrosive chlorine, fluoride and acidic volatile gas at high temperature, which quickly oxidizes ordinary stainless steel probe sheaths. Customized products use Hastelloy alloy as the outer protective layer, with fully sealed magnesium oxide filling inside to prevent corrosive gas from invading the thermocouple wire junction. For food-grade and medical transparent PP molds requiring no metal precipitation, the surface of the thermocouple sheath is polished to mirror finish to reduce plastic residue adhesion and facilitate mold cleaning.
Ultra-long customized thermocouples are used for large split manifolds of automobile whole vehicle exterior parts, with manifold lengths exceeding 1.2 meters. Standard fixed-length probes cannot reach the deep temperature measuring holes at both ends of the manifold, so manufacturers produce segmented assembly long probes with threaded connection structures, and each joint is equipped with high-temperature ceramic sealing rings to avoid heat loss. Special-shaped bent thermocouples are also required for stacked multi-layer manifold molds with staggered temperature measuring holes, which can be bent into L-type, U-type and Z-type according to mold processing drawings without breaking the internal thermocouple wires. All customized thermocouples need to pass 500-hour high-temperature aging test and air tightness test before delivery, and the drawings and size parameters are archived for subsequent spare parts replacement to ensure consistent matching performance.
