Impacts on Core Performance
Temperature Measurement Accuracy Deviation: The thermoelectric potential output characteristics of the thermocouple are directly altered by porosity, incomplete soldering, or unequal solder joint size within the solder balls. As a result, temperature measurement inaccuracies in the hot runner die head surpass ±5°C. This leads to imprecise temperature regulation, which eventually impacts the precision of injection-molded goods.
Significantly Shortened Service Life: Under long-term high-temperature cycling conditions in the hot runner, excessive oxidation, carburisation, or localised embrittlement of the thermocouple wires during the soldering process can result in rapid contact breakage and signal drift, directly reducing the service life by more than 30%.
Reduced On-Site Stability: Inadequate cleaning of solder ball surface residue and irregular solder joint shapes can easily result in poor contact and signal fluctuations under the hot runner's high temperature and vibration conditions. This can directly cause false alarms in the temperature control system and unscheduled production line downtime.
The Effects of Various Welding Methods on Quality
Argon Arc Welding: This method creates smooth, non-porous weld balls with strong welds by utilising argon gas for complete protection. With the best long-term dependability, it is the best welding solution for hot runner thermocouples.
Electric arc welding is easy to use but prone to contamination and carburisation. Near the weld point, the thermocouple wire is brittle and prone to breaking. Use of common base metal thermocouples is limited to non-high-precision applications.
Gas welding has a low operating threshold but inconsistent weld balls. After welding, residue needs to be cleaned right away to prevent residual flux from accelerating the thermocouple wire's ageing and corrosion.
Only ultra-fine thermocouple wires with a diameter of 0.03–0.3 mm can be welded using brine. When utilising this method, large-diameter hot runner thermocouples are very vulnerable to cold solder connections.
The quality of the weld balls in hot runner thermocouples is a crucial operation that needs to be controlled during daily hot runner system maintenance since it directly affects the temperature measurement reliability of the overall temperature control system.
