Complete incoming inspection standards for hot runner thermocouple spare parts cover dimensional measurement, material appearance, electrical performance, high-temperature stability and certification document verification, five core inspection modules with clear quantitative judgment criteria, effectively filtering unqualified low-quality probes before warehouse storage and avoiding production faults caused by defective spare parts after installation.
Dimensional measurement inspection is the first incoming check item, executed with digital calipers and micrometers to verify sheath outer diameter, total probe length, washer thickness, spring compression stroke and bending angle of bent probes. All dimensions must comply with the drawing tolerance range provided by the supplier; for brand-matched OEM spare parts, the tolerance standard is ±0.02mm, while compatible universal spare parts allow ±0.05mm. Any probe with over-limit size deviation is marked unqualified and returned directly, as dimensional mismatch will lead to loose contact or extrusion damage after installation. Ultra-miniature micro thermocouples additionally measure the flatness of button sensing heads with flatness gauges, rejecting deformed uneven heads that cause air gap heat transfer barriers.
Material appearance inspection checks sheath surface, spring structure and wire insulation quality. Qualified armored sheaths have uniform mirror polishing without rust pits, scratch abrasion, welding seams or pinhole corrosion. Spring components must rebound freely without deformation or elastic fatigue; extension cable insulation layers have uniform color without fading, cracking or brittle texture, and copper shielding braids are dense without missing braiding gaps. Probes with blackened oxidized sensing heads, frayed cables or deformed springs are classified as unqualified products and returned to suppliers.
Electrical performance inspection includes continuity test, polarity verification and short-circuit detection. Technicians use a multimeter to measure circuit continuity of each thermocouple; open-circuit probes are eliminated immediately. Wire color codes are checked against J/K standard rules to confirm positive and negative polarity matching, rejecting probes with reversed wire color marking that cause wiring errors on molds. The multimeter also tests for short-circuit between internal positive/negative wires and the metal sheath, filtering out probes with damaged internal insulation that induce grounding short-circuit alarms after installation.
High-temperature stability sampling inspection extracts 5% of each spare parts batch for dry-block calibrator three-point testing at 220℃, 320℃ and 380℃. Grade 1 precision thermocouples for automotive and medical molds must have deviation ≤±0.5℃ at all temperature points; Grade 2 packaging mold probes allow deviation ≤±1.1℃. Sampled probes with over-limit deviation are rejected, and the entire batch is subjected to full re-inspection. For corrosion-resistant alloy spare parts, additional 2-hour acid immersion sampling test is conducted to verify anti-corrosion performance of sheath materials.
Certification document verification checks complete supporting papers attached to each batch of spare parts, including raw material component test reports, IEC 60584 calibration certificates, RoHS environmental protection test reports and high-temperature aging test records. Medical and automotive grade spare parts must provide corresponding ISO13485 or IATF 16949 supporting documents; batches without complete formal certification files are put on hold and cannot be warehoused for production use.
All inspection results are recorded in incoming quality control logs with inspector signatures and batch serial numbers for traceability. Spare parts passing all five inspection modules are classified and stored in sealed dry cabinets according to J/K type and structural specifications. Strict standardized incoming acceptance checks eliminate unqualified thermocouple spare parts entering production lines, reducing post-installation temperature drift, alarm faults and molded part scrap losses by over 90%.
