How to Match Thermocouple Specifications for Different Hot Runner Nozzle Types

Different types of hot runner nozzles have different structural characteristics, installation space and temperature control requirements, and must be matched with targeted thermocouple specifications in terms of probe length, diameter, installation method and temperature resistance grade, so as to achieve the best temperature sensing effect.

Open type straight nozzle is the most commonly used in daily chemical and general plastic moulds, with simple internal construction and typical installation space. It is commonly used in combination with traditional K-type straight rod thermocouples of medium diameter and standard insertion depth, mainly for detecting the temperature of the nozzle tip to avoid freezing of the gate and drawing of wires.

The valve gate needle valve nozzle has a complex inner structure and assembly space. It mainly employs ultra-thin micro thermocouples or right-angle bent thermocouples to meet the layout of narrow hole position. Some high-end valve nozzles employ twin temperature measurement point thermocouples to monitor the middle part and the tip simultaneously, so as to realise segmented temperature control and avoid salivation and residual problems.

The side gate and angle type nozzles are restricted by the mould side embedding structure and straight-in thermocouples cannot be used. They need to be matched with the right-angle L-shaped bent thermocouples and bayonet quick-install thermocouples, which are easy to laterally install and disassemble.

The extended long nozzle used for deep cavity moulds requires customised ultra-long probe thermocouples to ensure that the temperature measuring head reaches the effective temperature sensing position of the nozzle tip, avoiding the problem of too shallow insertion causing delayed feedback and inaccurate temperature measurement. For particular nozzles for engineering polymers at high temperature, the upgrade of N-type high temperature resistant thermocouples and Inconel sheath materials is important to endure the long-term high temperature ageing.

The reasonable specification matching of the nozzle type not only can increase the temperature control precision and the yield of the products, but also can reduce the loosening, breakage and drift failure of the thermocouple, and can extend the overall matching service life of the hot runner nozzles.