2 Shot Injection Molding Process: A Reliable Manufacturing Process

Injection molding is a new technology that has revolutionized the plastics industry. This technology can be used to create very intricate designs and parts with a wide variety of materials. For different applications, there are different types of injection molding. One type is 2 shot injection molding, which is also called dual shot, multi-shot, or over-molding.

Figure 1 Two shot injection molding

Figure 1: 2 shot injection molding process

Two different materials are used to create one part in two-shot injection moulding. The industry often uses this technology to create products with two different colors or materials. This blog will explore the 2 shot injection molding process in more detail. Let’s start!

What is the 2 shot injection molding process?

Two shot injection molding or double-shot injection molding is a process where two different plastic materials are molded together in a single molding cycle. It is also called multi-component injection molding or over-molding. This process is categorized into two phases; one is similar to the conventional injection molding process, where melted plastic is injected into a mould to fill it.

Figure 2 2 shot injection molding process

Figure 2: 2 shot injection molding process

The second phase uses a robotic arm to place another layer of plastic on top of the first one. The two plastic materials can differ in color, texture, and hardness. This process mainly creates products with two or more different colors or materials.

For example, a product with a hard outer shell and a soft inner core can be made using the 2 shot injection molding process. The mold temperature control also prevents the two materials from mixing. This molding process is more complex and expensive than the conventional injection molding process, but it offers many benefits.

Significant advantages of dual shot injection molding

There are various advantages of using the 2 shot injection molding process for creating plastic products. Some of these advantages are listed below:

  • Complex mold designs

The 2 shot injection molding process makes it possible to create products with complex designs and features such as over-molding and inserts. This is because two different materials can be used in the same mould to create products with multiple parts or features. One can also use different types of materials to create products with different colors or textures.

  • Higher accuracy rate

Dual shot injection molding also offers a higher accuracy rate than other plastic molding methods. This is because the process allows for better control over the materials used. As a result, there is less chance of errors or defects in the final product. A higher accuracy rate means the products will be of better quality and more durable.

Figure 3 Multi shot injection mold

Figure 3: Multi-shot injection mold

  • Improved efficiency

Every process has to be carried out with utmost efficiency, so that time and resources are saved. The 2 shot injection molding process is a very efficient one as it offers shorter cycle times and lesser material waste. This means that products can be created faster and at a lower cost. The final products will also be of better quality and will have a longer lifespan.

  • Part consolidation

The 2 shot injection molding process can be used to consolidate multiple parts into one. This is done by creating an over-molded part with all the individual parts’ features. In addition, it is also possible to insert metal or other materials into the plastic product. This helps to create products that are stronger and more durable.

  • Lower tolerance

For any product to be of good quality, there must be lesser tolerance. The 2 shot injection molding process offers lower tolerance levels than other methods. With this process, you can be sure of getting products with the same color and features.

What is the difference between insert molding and over-molding?

Insert molding is the process of molding a part around an insert or core. The insert is usually placed in the tool before any polymer is introduced. Overmolding is the process of molding a part over another part or substrate. Combining both methods into one process called 2 shot injection molding or multi-shot injection molding is also possible.

4 Difference between insert molding and overmolding

Figure 4: Difference between insert molding and over-molding

Insert molding can create parts with complex geometries or multiple cavities. It can also combine dissimilar materials, such as metal and plastic. But in recent times, over-molding has become increasingly popular because it is an advanced plastic molding process that allows you to create two or more different plastic products from one single tool. It involves injecting two different polymer materials into the same mold.

The word shot is used to describe the amount of material that is injected into the mold during the injection molding cycle. So, 2 shot injection molding means injecting two shots or two different materials into the same mold.

Potential application of two shot injection molding

Figure 5 Applications of 2 shot injection molding

Figure 5:  Applications of 2 shot injection molding

2 shot molding can be used for a wide variety of applications, such as:

  • Creating multi-color components

One of the most popular applications for 2 shot injection molding is creating multi-colour components. Two different colors of plastic can be injected into the same mold, creating a component that is two colors. This can be used to create components with multiple colors, or to create components with color gradients.      

  • Movable components and segments

Two shot injection moulding can be used for applications where a component needs to be movable or have moving segments. A softer plastic can be injected first to create a “shell”. This shell can then be filled with more rigid plastic, creating a strong and durable component that can still move. With two-shot molding, it is possible to create hinges, living hinges, and other moving components.

  • Acoustic dampening or vibration

This type of moulding process can be used to create components with acoustic dampening or vibration properties. This is done by injecting a material with these properties into the core of the component and then encapsulating it with a different material. It is also possible to create different durometer zones within a single component using two-shot injection molding.

  • Dental products

It can create a wide variety of dental products, such as toothbrushes, retainers, and mouthguards. The first material that is injected can be softer and more flexible, while the second material can be harder and more durable. This allows for creating products that are both comfortable to use and long-lasting.

  • Two-toned plastic lenses

With dual shot molding, two-toned plastic lenses can be created. This is done by injecting a material with a different refractive index into the core of the lens. This creates a lens with two colors and different properties in different areas. It is also possible to create gradient lenses using 2 shot injection molding.


Go4mould is the most reliable and trustworthy supplier in China; they have the most complete technology in two-colour injection molding. Go4mould also offers several different moulds, including test tube mold, plastic box mould, fresh box mould and many more. 

All the services and products have gone through under strict quality control. With the most reasonable price, Go4mould is the best partner for your business. For quotes or more information, feel free to contact us anytime.

2 shot injection molding process-FAQs

1. What is shot capacity in injection molding?

The shot capacity is the maximum amount of plastic injected into the mold. If you try to inject more plastic than the shot capacity, the mould will not close properly, and you will not be able to produce a usable product.

2. What materials are best for two-shot injection molding?

There are a wide variety of materials that can be used for 2-shot injection molding. The most common material is polycarbonate, but other materials such as ABS, nylon, and PVC can also be used. It depends on the application and the desired properties of the final product.

Related reading: Two-shot injection molding companies in China 2024

Scroll to Top