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What is Hot Runner System?

Views: 9     Author: Site Editor     Publish Time: 2022-12-19      Origin: Site

A hot runner system is a conveying device used in injection molds that is applied to a system for conveying molten plastic into the mold. A hot runner system usually consists of internally heated parts of a plastic injection mold. The function of the hot runner is to bring the molten plastic from the barrel of the injection molding machine into the mold's cavity. The size of the hot runner melt channel varies depending on factors such as injection speed, resin type, molded parts, and fill rate.


How hot runner system work.

When using a hot runner for injection mold processing, the temperature controller first heats the hot runner system and the resin in the barrel of the injection mold, ramping up to the desired working temperature and subsequently injecting the resin into the mold. The resin passes through the inlet, down into the manifold, and then diverts to the individual nozzles and through the injection point into the final mold cavity to form the needed part. As a professional precision parts mold manufacturer, Shengqi can offer a selection of molds with 1-192 nozzles, which can meet your needs for various plastic mold-making requirements.


Before the advent of hot runner technology, cold runner systems were more commonly used on injection molds. But cold runner molds still have difficulties transporting the resin from the barrel to the cavity without affecting its properties and thermal performance. And as resin types evolve and mold and part design need become more diverse and complex, it is becoming increasingly challenging to make qualified parts by mold molding with cold runner systems.


Therefore, hot runner systems with more advanced thermal control and the ability to process a broader range of resins are a more practical and convenient option for injection molders. Unlike cold runner molds, hot runner components are individually heated to ensure that the resin remains at a constant temperature throughout the mold. The temperature of each hot runner heated component can also be precisely controlled to ensure that the process is optimized for the requirements of each resin, providing the highest possible part quality. Today, hot runners remain one of the dominant processes in plastic mold processing, capable of producing a wide range of sizes and complex parts to meet the part needs of various industries.

Hot-Runner-System-1


Elements of a hot runner

Positioning Ring: The positioning ring aligns the injection mold with the platen of the molding machine. It ensures that the mold is properly aligned with the machine.


Inlet: When the resin is injected into the mold, this is the inlet where the resin enters through the injector nozzle. Depending on the resin type and the hot runner's design, the inlet assembly can be heated to optimize the molding process.


Manifold: The manifold allows the resin to flow into different nozzles and injection points (gates). Manifolds are typically used to inject multiple cavities or where multiple nozzles/gates are required per part. Manifolds are available in various materials, designs, and shapes and are often optimized to improve the molding process using CAE analysis. There are two main manufacturing Techniques: gun drilling and 2-piece brazing. Gun drilling is often ideal for simpler, more economical systems, while 2-piece brazing is often preferred when more stringent performance criteria (balance, faster color change) are required. 2-piece manifolds are also ideal for multi-material or multi-color molding applications.


Nozzle: The nozzle is the component through which the resin is injected into the cavity through the gate. Depending on the design, the nozzle is typically mounted in a mold plate with or without a manifold. Various nozzle designs are available, using different materials to achieve the processing characteristics of the various resins best suited to the application.


Heater Technology: Heater technology is the foundation of all hot runner systems and significantly impacts the molding process and part quality. Several heating options are available, each with its advantages and disadvantages. Choosing the proper hot runner depends on the requirements of the molding process, part performance, reliability, and cost. The most typical hot runner technologies are heaters with heater bands/plates, stick-on/flex heaters, or brazed heaters.


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