Types of Hot Runner Systems

This division of the subject will make the understanding of HR technology easier. 

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The principal types are two-plate, three-plate, and stack molds. Others include the family mold that has multiple cavities of different shapes in one mold.3, 324 A further distinction concerns the feed system that can be either the cold or hot type. These classifications overlap. Three-plate molds will usually have a cold runner feed system, and a stack mold will have a hot runner system. Two-plate molds can have either feed system. 

The insulated runner type of runnerless mold and certain types of hot sprue bushings can be used for UPVC, however careful consideration needs to be given to the relative thermal stability of the molding compound (i.e. the type of stabilizer system used) and the anticipated cycle time at which the mold is expected to run at before deciding which approach to opt for. 

Thus, all the benefits of the system nozzles can be used for single applications without a hot runner manifold, even If not driven with an adjacent machine nozzle. The nozzle bodies are usually made from special hot work steel. This guarantees a high compressive strength, even for continuous temperatures well above 300 °C. With these nozzle concepts, plastics with filler contents of more than 40% and VO-adjusted materials at injection pressures of 2,000 bar or more can be reliably processed. Figure 2.58 shows a typical representative of the manufactured products family with this nozzle series. High processing temperatures, a narrow process window, and the risk of abrasive and chemical wear of the mold components are characteristic of this type of technical components. 

The application of this type of standard specification makes possible manufacturing of moulds with a minimum injection by the precise separation of the cold sprue from the hot cavity. The sprue markings are minimal thanks to the pneumatic needle sealing system. Cycle times can be reduced because of the high temperatures of the cavity. As an ARBURG standard for example, cold runner systems are offered with up to four gate points. 

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