Hot runner systems are feed systems for injection molds which convey molten plastic from the machine nozzle into the cavity.
Hot runner systems are composed of different parts and mechanisms:
- Nozzles: Nozzles are the melt delivery system. Nozzles are designed to inject and distribute molten polymer to a number of cavities.
- Manifolds: It is a heated melt-distribution system with channels. This structure can be in different shapes as I, H, X, Y or any demanded shape.
- Flow control: Valve technology to control the melt flow.
- Temperature controller
- Connections/Parts: All relevant connections as electrical, resistors, thermocouple…
Hot runners may be classified according to how they are heated. There two main types of hot runner systems:
For heated runner systems, there are two designs: internally heated and externally heated. The first is characterized by internally heating. The resistor is placed directly in the melt channel and heats the material from the inside. The second consists on manifold is heated with interior flow passages. The manifold is designed with various insulating features to separate it from the rest of the mould, thus reducing heat transfer.
This system allows the molten polymer to flow into the runner, and then it is cooled to form an insulating layer of solid plastic along the walls of the runner.
Hot Runner System Advantages
- Easier fully automatic operation.
- No loss of melt.
- Pressure losses minimized.
- Increase of mechanical efficiency.
- Improvement of product quality.
- Extension of mold life.
- Shorter cycles.