What conditions do you need to use hot runner system in the two-color mold manufacturing?

1. What is a two-color mold?

Two-color mold refers to two plastic materials that are injection molded on the same injection machine and molded in two parts, but the product only release once. Generally, this molding process is also called double-material injection molding, usually completed by a set of molds, and requires a special two-color injection molding machine.


Two-color molds are becoming more and more popular on the market today. This process can make the appearance of the product more beautiful, easy to change colors without spraying, but has high requirements for design and injection molding.


2. What is a hot runner system?

In the plastic injection mold, in order to promote the flow of the plastic melt in the cavity, the main channel and the branch channel are heated by an appropriate method to keep the plastic in a molten state, and the continuous injection molding structure is a hot runner system.


3. What are the advantages and disadvantages of the hot runner system?


  1. Save raw materials, reduce injection cycle and increase production efficiency.
  2. The raw material is 100% productive, which reduces the defects caused by the secondary material.
  3. Improve product quality (pressure, reduced internal stress of the product).
  4. Extend the life of the mold.
  5. No need to reserve the runner position, reduce the size of the mold. Easy to set the gate position



  1. The cost of molds has risen.
  2. Maintenance of the warranty requires professional personnel.
  3. The mold design should be fully tested.


4. In which case, do you need to use hot runners in the manufacture of two-color molds?

In the manufacture of two-color molds, hot runners are sometimes used, and hot runner molds are molds that use a heating device to keep the resin melt in the runner from solidifying at all times. Because it is shorter than the traditional mold forming cycle and saves raw materials, hot runner molds are widely used in various industrialized countries and regions in the world today.


The hot runner system is required in the following situations:

  1. Injection moldings with strict quality requirements.
  2. A variety of plastic, multi-color co-injection process.
  3. The gate direction is at a certain or perpendicular angle to the mold opening direction.


Multilayer molds One way to increase production without increasing the tonnage of the injection molding machine is to use a multi-layer mold. That is, there are multiple parting faces on the mold. This type of mold is completely realized by the hot runner system.

The gates are designed inside of deep parts. Some industrial products are extremely strict in appearance. In use, do not expose any gate marks on small parts such as cosmetic lipstick caps and automotive interior parts. At this time, the gate needs to be designed inside the part. When the depth of the part is too large, it is impossible to use the cold runner gate, and only the hot runner nozzle can be used to form the inside of the part for injection molding.


5. What are the benefits of hot runners for molds?

Shortening the molding cycle, many thin-walled parts produced with hot runner molds can be molded for less than 5 seconds.

Save plastic raw materials, no production costs in pure hot runner molds. It is an effective way to reduce the cost of materials and materials.

Reduce costs and improve product quality.

Eliminating subsequent processes is conducive to production automation.

Expand the application of injection molding process.

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