Hot runner technology is the generic term for the manufacture and application of hot runner systems which are used as functional components of forming tools for the machine production of molded parts made of metals or engineering plastics.
In the injection molding of thermoplastics, hot runner technology or the hot runner systems in the sprue system of the molds are of decisive importance. The most important function of hot runner technology is the precise and reliable temperature control of the plastic melt flowing into the mold. When a hot runner system is used, the sprue system is thermally separated from the mold environment and is tempered separately to ensure the flowability of the melt. The plastic cannot solidify and no sprue forms on the molded part. Hot runner systems also allow longer flow paths to be realized, as they prevent both pressure losses in the gating system and viscosity increases in the cooling melt. Modern hot runner systems can be controlled very precisely. Functional components of hot runner systems for heat supply are, for example, cartridge heaters, coil heaters or flexible tubular heaters. However, precise monitoring of the temperature in the hot runner is also crucial to ensure a smooth process. Different tree shapes of thermocouples are used for this purpose. Specifically, mineral insulated thermocouples with diameters of Ø 1.0 mm and Ø 1.5 mm or thermocouples with a flange mounting (also called type 68) are often used here.
Structure of a hot runner system
A hot runner consists of the hot runner manifold bar and the hot runner nozzles. The liquid melt comes from the plasticizing unit and flows through the manifold bar to the nozzles. The nozzles are the last heated zone before the liquid plastic enters the injection mold for cooling.
Cascade injection molding
Cascade injection molding is possible with hot runner technology, which enables the production of large components. Due to the numerous nozzles in the hot runner, multiple gates can be used to fill the molded part.
Who builds hot runner systems?
Hot runner systems are a separate manufacturing division. They are usually not manufactured by the mold and die shop but are purchased as a purchased part for the mold. Numerous companies have developed in the industry whose sales model is based solely on the manufacture of hot runner systems.
What is a mold?
A forming tool is a complex, two-part construction, made of steel, aluminum or cast iron, depending on the application, and often containing complex temperature control systems and hot runner systems.
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