Different Types of Injection Molds: A Comprehensive Guide



1.Introduction to Injection Molding

2. Different Types of Injection Molds

   2.1 Two-Plate Molds

   2.2 Three-Plate Molds

   2.3 Stack Molds

   2.4 Family Molds

   2.5 Hot Runner Molds

   2.6 Cold Runner Molds

3. Factors to Consider When Choosing an Injection Mold

4. Conclusion

1. Introduction to Injection Molding

Injection molding is a popular manufacturing method used to create a wide range of plastic products, from small components to large, complex structures. The process involves heating plastic resin pellets to their melting point, then injecting the molten material into a mold cavity. Once the material cools and solidifies, the mold is opened, and the finished part is ejected.

2. Different Types of Injection Molds

There are several types of injection molds, each with its advantages and disadvantages. Here, we will discuss six common types:

2.1. Two-Plate Molds 

Two-plate molds are the simplest and most common type of injection mold. They consist of two halves – a cavity and a core – which are held together by a clamping mechanism. When the plastic material is injected into the mold, it fills the cavity, taking the shape of the desired part. Two-plate molds are cost-effective and suitable for parts with simple geometries.

2.2. Three-Plate Molds 

Three-plate molds are more complex than two-plate molds, featuring an additional intermediate plate. This design allows for better control of the material flow and part ejection. Three-plate molds are ideal for intricate parts with multiple cavities or when automatic degating is required.

2.3. Stack Molds 

Stack molds have multiple mold cavities stacked on top of each other, increasing the number of parts produced per molding cycle. This type of mold is ideal for high-volume production and can significantly reduce cycle times and overall costs. However, stack molds require a larger molding machine and can be more expensive to manufacture.

2.4. Family Molds 

Family molds are designed to produce multiple, different parts within a single mold. They are useful for manufacturing a set of related components that will be assembled later. Family molds can save on cost and production time by reducing the number of individual molds required. However, the complexity of the mold design and the need for balanced cooling and filling can make family molds challenging to produce.

2.5. Hot Runner Molds

Hot runner molds use a heated manifold system to keep the plastic material in a molten state as it flows through the mold. This type of mold eliminates the need for a cold runner system, reducing waste and improving cycle times. Hot runner molds are suitable for large-scale production and can result in significant cost savings over time.

2.6. Cold Runner Molds

Cold runner molds use unheated channels to guide the molten plastic material to the mold cavities. This type of mold is simpler and less expensive than hot runner molds but can result in higher material waste due to the solidification of the plastic in the runners. Cold runner molds are a good choice for low-volume production or when using heat-sensitive materials.

3. Factors to Consider When Choosing an Injection Mold

When selecting an injection mold, consider the following factors:

a. Part geometry and complexity

b. Production volume

c. Material type

d. Budget constraints

e. Cycle time requirements

f. Assembly requirements

Each type of injection mold has its advantages and disadvantages, so it's essential to carefully consider the specific needs of your project.

4. Conclusion

Injection molding is a versatile and efficient manufacturing process, capable of producing a wide range of plastic parts. By understanding the different types of injection molds and their applications, you can make informed decisions when selecting the right mold for your project. Whether you're working with simple geometries or complex, multi-component assemblies, there's an injection mold type suitable for your needs.


1. What factors affect the quality of the injection molding process?

Several factors can affect the quality of the injection molding process, such as the design of the mold, the quality of the plastic material, the temperature and pressure of the injection, and the cooling time of the product.

2. What is injection molding?

Injection molding is a process of manufacturing plastic products by injecting molten plastic into a mold. The plastic solidifies inside the mold to produce the desired shape.

3. What types of plastics can be used in injection molding?

There are various types of plastics that can be used in injection molding, including polyethylene, polypropylene, PVC, nylon, and many more.