What is Dual Injection Molding?

What is dual injection molding?

Dual injection molding, or co-injection or two-shot injection, is a commonly used plastic injection molding technology. It can complete the injection molding of two materials by one injection machine to produce plastic products with different colors, materials, or textures. Through this technology, products can with more complex designs and diversified functions. Compared with encapsulation technology, dual injection molding reduces the assembly process and secondary processing costs.

The basic principle of dual injection molding technology is injecting two different molten plastics into the mold. With the rotary table to change the mold, the first and second injections combine two kinds of materials to be a product.

What advantages of dual injection molding technology?

1. High degree of design freedom.
   Dual injection molding can realize the combination of various plastic materials, colors, and textures to design more diversified products.
2. Reduce costs.
   Compared with the traditional assembly process, dual injection molding can reduce the operation and human resources on the assembly cost and production cycle.
3. High production efficiency.
   Dual injection molding can complete the injection and molding of two materials simultaneously, with higher production efficiency and more stable product quality.

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What technology is involved in double injection?

Dual injection molding technology injects two different plastic materials in the same mold simultaneously to achieve different color and texture effects. It is the cooperation of "dual injection mold" and "dual injection molding machine."

First, regarding the dual injection mold, the final plastic product must be considered in the design.

1. Product shape and size.
   The shape, size, complexity, and other product factors (such as thread) affect the design of the flow channel, cavity, positioning, and opening and closing mechanism of the mold.
   • Regarding runner and cavity design：
     The design of runners and cavities is one of the mold design cores. Designers must design based on the final product's shape, size, and structural complexity. They also need to consider the plastic's Physical properties, such as fluidity, injection pressure, filling time, and other factors, to design the flow channel.
   • Regarding the design of positioning and opening and closing mechanism：
     It ensures the precise alignment of the two mold bases (male mold and female mold). When designing these mechanisms, it is necessary to consider mold size, weight, rigidity, and other factors.
2. Design of mold cooling system.
   The design of the mold cooling system affects the production cycle, product quality, and production cost.
   • Location of the cooling system:
     When designing the cooling system, it's at the thickest part of the mold for better cooling of the entire mold
   • Piping design of the cooling system:
     The pipeline should be kept unobstructed to ensure that the cooling water can flow evenly through the entire mold, and enough inlets and outlets should be designed to adjust the flow and pressure of the cooling water.

Secondly, regarding the dual injection molding machine, it is necessary to cooperate with the dual injection mold design.

1. Injection unit:
   The injection molding machine equips with two injection systems that can operate independently to process two different materials/colors respectively.
2. Clamping unit
   The distance between the tie bars can accommodate two sets of molds (or possibly designing one pair with a left-right symmetrical design), and relying on the rotation of the table (or the shaft), that one-shot injection product is diverted to the two-shot injection to achieve dual injection molding.

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Where can dual injection molding be applied?

Dual injection molding technology has a wide range of applications.

1. Auto parts (in the automotive industry):
   To produce automotive interiors, exterior parts, lights, doors, and other parts can make auto parts meet higher appearance, function, and performance requirements while reducing production costs.
2. Home appliances ( in the houseware industry) :
   To produce various home appliances, such as mobile phone cases, disposable wavetables, buckets, baskets, etc. It can make the appearance of the products more beautiful and, at the same time, enhance the functions and performance of the products.
3. Medical devices (in the medical industry):
   To produce various medical devices, such as syringes, pipeline connectors, etc.
4. Sports equipment (in the sports industry):
   To produce various sports equipment, such as skateboards, bicycle frames, fitness equipment, etc. It can make the product's appearance more attractive and, at the same time, enhance the function and performance of the product.

In general, dual injection molding technology has a wide range of applications. It can improve product quality and performance while reducing production costs. It is an essential technology in the plastics processing industry.

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