Hot Runner System Wiki

  • August 21, 2019
  • Categories: Blog

Hot Runner Systems is used in the injection mold and it injects the melted plastic particles into the mold cavity of the heating assembly system. Hot runner mold is a new structure that heats the runner of traditional or three-plate mold, which is not need to take out the runner and runner during each forming.

  1. Overview
  2. Hot Runner Advantages
  3. Hot Runner Types
  4. Hot Runner Structure
  5.  

1. Overview

The hot runner is to ensure that the plastic in the runner and gate remains molten by heating. Because of the heating rod and heating ring near or in the center of the flow channel, the whole flow channel from the nozzle exit to the gate of the injection molding machine is in a high temperature state. So the plastic in the flow channel can remain molten. After shutdown, it is generally not necessary to open the runner to remove the condensate, and then only need to heat the flow channel to the required temperature. Therefore, hot runner process is sometimes called heat pressure manifold system, or non-runner molding.

2. The advantages and disadvantages of hot runner technology

2.1 Advantages

  • Saving raw materials and reduce costs.
  • Shortening the molding cycle and improve the efficiency of the machine.
  • Improving the surface quality and mechanical properties of the products.
  • A point gate can be used without using a three-plate mold.
  • A single product can be molded economically with a side gate.
  • Improving the degree of automation.
  • Needle valve gate can be used to control gate freezing.
  • The quality of the injection molding parts of the multi-mold cavity die is the same.
  • Improving the surface beauty of injection molding products.
  • Smaller injection pressure can be used, which can effectively reduce the post-variant of thin-wall products.

2.2 However, each technology has its own shortcomings, and hot runner technology is not an exception.

  • The mold is complex in structure, high in cost and in maintenance cost.
  • It takes some time for the process to stabilize, resulting in more waste products at the beginning.
  • Melt leakage and heating element failure has great influence on product quality and production progress.

3. Hot Runner Types

The hot runner system is divided into the fully hot runner and the semi hot runner system. The design of the fully hot runner is complex, but it has good effect and very low maintenance cost. The semi hot runner is simple in structure, and it is stable and easy to use. Its failure rate is low, structure is simple and maintenance cost is low, so it has greater assurance on the stability of production.

Classification of hot runner: One is Open Type (for the semi hot runner system), the other one is Needle Valve Type (for the fully hot runner).

3.1 Open Type (For the Semi hot runner system)

Open type hot runner is simple in structure. It is suitable for semi hot runner system but not fully hot runner. The fully hot runner is limited in material it is easy to draw and leak because it contacts the surface of the product directly. The surface quality is poor. The semi hot runner does not contact the product but touches the micro flow channel so it can use open hot nozzle. It is widely used in high precision die abroad.

3.2 Needle Valve Type (For the Fully hot runner system)

The needle valve hot runner can save material. The surface of the plastic part is beautiful and the internal quality is close and the strength is high. There are two kinds of needle valve hot runner in the world: Cylinder needle valve hot runner and spring needle valve hot runner.

Cylinder needle valve hot runner controls the closing of the needle valve driven by the cylinder by the controller and the timing controller. The structure is complicated but the design is simple. The Main suppliers are DME (USA), INCOE (USA), MOLD-MASTER (Canada), HUSKY (Canada),  etc.

Spring needle valve hot runner is only made by FISA (Japan). The largest feature is that it uses spring and injection pressure balance to control needle valve switch. Its assembly, debugging and maintenance is simple, mold accuracy is not high, it is widely used in home appliances, automobile trim and precision multi-cavity mold.

 

4. Hot Runner Structure

The hot runner system is generally composed of hot nozzle, shunt plate, temperature control box and accessories. Hot runner nozzles generally include two kinds: open hot nozzles and needle valve hot nozzles. Because the form of hot nozzle directly determines the selection of hot runner system and the manufacture of mold, the hot runner system is often divided into open hot runner system and needle valve hot runner system. Shunt plate is used when mold multi-cavity or multi-point feed, single point feed but material level bias. Materials usually use P20 or H13 (1.2344, SKD61). The distributary part is generally divided into two categories: standard and non-standard. Its structure is mainly determined by the distribution of the cavity on the die, the arrangement of nozzles and the gate position. The temperature control box includes mainframe, cable, connector and male and female socket. Hot runner accessories usually include heaters and thermocouples, runner sealing rings, connectors and junction boxes.

3.1 Open Type (For the Semi hot runner system)

Open type hot runner is simple in structure. It is suitable for semi hot runner system but not fully hot runner. The fully hot runner is limited in material it is easy to draw and leak because it contacts the surface of the product directly. The surface quality is poor. The semi hot runner does not contact the product but touches the micro flow channel so it can use open hot nozzle. It is widely used in high precision die abroad.

3.2 Needle Valve Type (For the Fully hot runner system)

The needle valve hot runner can save material. The surface of the plastic part is beautiful and the internal quality is close and the strength is high. There are two kinds of needle valve hot runner in the world: Cylinder needle valve hot runner and spring needle valve hot runner.

Cylinder needle valve hot runner controls the closing of the needle valve driven by the cylinder by the controller and the timing controller. The structure is complicated but the design is simple. The Main suppliers are DME (USA), INCOE (USA), MOLD-MASTER (Canada), HUSKY (Canada),  etc.

Spring needle valve hot runner is only made by FISA (Japan). The largest feature is that it uses spring and injection pressure balance to control needle valve switch. Its assembly, debugging and maintenance is simple, mold accuracy is not high, it is widely used in home appliances, automobile trim and precision multi-cavity mold.

 

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