What is Dual Injection Molding?

In plastic injection molding, efficiency, quality, and innovation are key. Dual injection molding offers a unique set of advantages for complex plastic parts. While it may seem more complex or expensive at first glance, dual injection molding can actually be a cost-effective solution that enhances functionality and saves time. The following will give a detailed introduction to dual injection molding, its advantages, and its applications.

Dual injection molding, also known as two-shot, multi-shot, or double-shot molding, is a commonly used plastic injection molding technology that allows engineers to create multi-material or multi-colored parts without adding extra assembly steps. It can complete the injection molding of two materials by one injection molding 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.

Dual shot injection molding is a process where two different plastic resins are molded together in a single machining cycle. This process involves two phases:

1. First Shot: A resin is injected into a mold and cooled to form a solid part.
2. Second Shot: The just-molded part is transferred to a second mold and receives a second shot of resin, forming a molecular bond.

Dual injection molding offers a range of benefits that make it an attractive option for producing complex plastic parts:

• High Degree of Design Freedom: Double shot molding enables the combination of various plastic materials, colors, and textures, allowing for more diversified product designs.
• Cost Reduction: Compared to traditional assembly processes, double shot molding can reduce costs associated with operations, labor, and production cycles.
• High Production Efficiency: Dual shot molding can complete the injection and molding of two materials simultaneously, leading to higher production efficiency and more stable product quality.
• Part Consolidation: Reduces the number of components in a finished assembly, saving on development and engineering costs.
• Improved Efficiency: Allows multiple components to be molded with a single tool, reducing labor and post-molding assembly.
• Improved Quality: Enables lower tolerances, high accuracy, and reduced scrap rates.
• Complex Moldings: Allows for the creation of complex mold designs with multiple materials.

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

Dual injection mold

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.

Dual injection molding machine

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.

Further reading：How to choose a suitable injection molding machine? From the machine itself and plastic product!

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.

Further reading：Applications > Video - HUARONG GROUP

We proposed the use of dual injection molding for consumer goods, automotive, and other industries to meet the client's design needs. This process allows for the combination of different materials, colors, and textures in a single process. For the headphone outer cases, we utilized a combination of hard and soft materials to achieve a durable yet comfortable design. Similarly, for the hair clips, we employed dual injection molding to create intricate designs with multiple colors and textures.

Dual shot molding case study 1: How the Production of Headphone Outer Cases Works?

Dual shot molding case study 2: How To Make Your Own Dual Color Hair Clips

Dual injection molding is a versatile and cost-effective solution for producing complex plastic parts such as headphone outer cases and hair clips. Its ability to combine different materials, colors, and textures in a single process makes it ideal for various applications in the electronics and fashion industries. If you are searching for a dual injection molding machine, Huarong is an experienced injection molding machine manufacturer who offers professional advice; feel free to contact Huarong.

• Group Name: Huarong Group
• Brand: Huarong, Yuhdak, Nanrong
• Service Offerings: Injection Molding Machine, Vertical Injection Molding Machine, Injection Molding Automation
• Tel: +886-6-7956777  #521
• Address: No.21-6, Zhongzhou,Chin An Vil., Xigang Dist., Tainan City 72351, Taiwan
• Official Website: https://www.huarong.com.tw/

Feel free to contact us.

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