Different types of hot runner nozzles have distinct 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 widely used in daily chemical and general plastic molds, with simple internal structure and conventional installation space. It is usually matched with conventional K-type straight rod thermocouples with medium diameter and standard insertion depth, focusing on sensing nozzle tip temperature to prevent gate freezing and wire drawing.
Valve gate needle valve nozzle has complex internal structure and compact assembly space. It mostly adopts ultra-thin miniature thermocouples or right-angle bent thermocouples to adapt to narrow hole position layout. Some high-end valve nozzles use double temperature measuring point thermocouples to monitor the middle section and tip at the same time, realizing segmented temperature control and avoiding salivation and vestige defects.
Side gate and angle type nozzles are limited by mold side embedding structure, and straight-in thermocouples cannot be installed. They need to be matched with right-angle L-shaped bent thermocouples and bayonet quick-install thermocouples, which are convenient for lateral installation and later disassembly.
Extended long nozzle used for deep cavity molds needs customized ultra-long probe thermocouples to ensure that the temperature measuring head reaches the effective temperature sensing position of the nozzle tip, avoiding too shallow insertion leading to delayed feedback and inaccurate temperature measurement. For high-temperature special nozzles used for engineering plastics, it is necessary to upgrade to N-type high-temperature resistant thermocouples and Inconel sheath materials to resist long-term high-temperature aging.
Reasonable specification matching according to nozzle type can not only improve temperature control accuracy and product yield, but also reduce thermocouple loosening, breakage and drift failure, and extend the overall matching service life of hot runner nozzles.
