Different hot runner gate types determine the melt outlet mode and heat distribution characteristics, and directly restrict the installation position, angle, type and quantity matching of thermocouples, which is an important basis for early measuring point layout design.
For open sprue gates with simple structure and smooth material flow, the heat distribution is uniform and the temperature fluctuation range is small. Thermocouples can adopt conventional straight rod type, arranged in the middle stable heating section of nozzles, with standard installation depth to realize stable temperature monitoring, and the layout difficulty is low with fewer quantity demands.
For needle valve gates widely used in high-precision products, the internal movement of valve needles leads to complex local heat transfer, and the temperature near the gate changes obviously during opening and closing. It is necessary to arrange high-sensitivity bent thermocouples close to the front end of the gate to monitor the instantaneous temperature change of melt during switching, so as to effectively avoid defects such as wire drawing, material dripping and gate material solidification.
For side gate and latent gate hot runners limited by mold structure, the installation space is narrow and blocked. Conventional straight thermocouples cannot be installed in place, so short-type angle-adjustable thermocouples must be selected to bypass structural obstacles and accurately reach the designated temperature measuring area.
In addition, large thin-film gate hot runners have wide melt outflow range and obvious temperature difference in different areas, so it is required to increase the number of auxiliary thermocouples for regional balanced temperature detection. Fully combining the structural characteristics of different gates to formulate targeted thermocouple layout schemes can maximize the temperature control effect and stabilize product molding quality fundamentally.
