Three Types of Injection Molds: What You Need to Know

Three Types of Injection Molds

Injection molding is a process for manufacturing plastic parts from plastic materials. There are many different types of injection molds, and it can be hard to know which type is right for your project. This blog post will explore the most common injection mold types and discuss each type’s benefits and drawbacks.

3 Main Types Of Injection Molds

Injection molding is a popular manufacturing process used for creating plastic parts. There are three main types of injection molds in this process:

According To The Feeding System

Hot Runner Injection Mold

Hot runner is an injection molding system where the plastic runners are kept at an increased temperature to stay melted and ready to inject.

It helps to reduce the overall cycle time because the plastic does not need to be reheated between injections. And hot runners can help improve the finished product’s overall quality by minimizing the risk of defects such as cold spots.

Hot runners also have some disadvantages. They are typically more expensive than cold runner systems and require more maintenance and care. Additionally, hot runners can be more difficult to troubleshoot if problems arise.

Hot vs. Cold Runner Injection Mold

Cold Runner Injection Mold

A cold runner injection mold is a mold that does not have a hot runner system. The molten plastic is injected directly into the cavity through the sprue hole. The runners are attached to the mold but solidify with the molded parts. Cold runner molds are generally suitable for large production runs because they are more economical.

The main advantage of a cold runner injection mold is that cleaning up the runners after each cycle is unnecessary, as they solidify along with the parts. Cold runner molds typically have a longer lifespan than hot runner molds because there is no risk of damage to the hot runner system.

Cold runner molds can be more challenging to design and produce, and they typically have a higher reject rate than hot runner molds.

Insulated Runner Injection Molds

An insulated runner injection mold can reduce the heat lost during the injection molding process. The mold is made up of two parts: a heated outer shell and an inner core that is filled with insulation material.

The insulation material helps keep the heat in the outer shell, which helps keep the molten plastic temperature more consistent. As a result, the finished product is less likely to have defects caused by fluctuations in temperature.

Advantages to using an insulated runner injection mold.

  • Enhance the quality of the finished product overall.
  • Increase the production efficiency of the injection molding process.
  • Reduce energy consumption by keeping the molten plastic at a more consistent temperature.

Disadvantages to using an insulated runner injection mold as well.

  • The cost of buying and maintaining the mold can be pretty high.
  • If the insulation material is not maintained correctly, it can lead to problems with the finished product.
  • Removing the finished product from the mold can be challenging if the mold is not designed correctly.

According To The Mold Plate


Two-plate injection molds are the simplest type and consist of only two halves: the A side (cavity side) and the B side (core side). 

The B side includes the sprue bushing through which molten material is injected into the mold.

The A side contains the cavity into which plastic material flows to form the desired shape.

Although two-plate molds are simple in design, you need to consider several advantages and disadvantages when deciding if they are the correct type of mold for your application.

Two-Plate injejction mold


  • Reduced cycle time. There are no moving parts in a two-plate mold.
  • Reduced cost. Two-plate molds are less expensive than multi-plate molds because they have fewer parts and require less machining. 


  • Limited design options. Two-plate molds have limited design options because only two plates are involved. This can be a problem when creating more complex shapes or geometries. 
  • Increased risk of flash. There are no ejector pins on the b side of a two-plate mold, and there is an increased risk of flash (excess material) on the part when it is ejected from the mold.
  • Limited lifecycle. Two-plate molds typically have a shorter lifespan than multi-plate molds because they are subject to higher stresses during injection and ejection due to the lack of support from an ejector plate.


A three-plate injection mold is a type of mold that has three separate plates that come together to form the mold cavity. This design is typically suitable for larger molds, providing excellent support and stability. It also allows for more intricate designs, as the plates can be machined to exact tolerances.

The main advantage of a three-plate mold is that it can be used to create very large or complex molded parts. The disadvantage is that it is more costly and time-consuming than a two-plate mold.

Three-plate molds are more likely to warp or distort over time due to the increased forces exerted on the plates.

Three-Plate mold

According To The Number Of Cavities

This category includes three types of injection molds based on the number of parts they can produce per molding cycle. These include:

Single Cavity

A single cavity injection mold is a tool to create multiple copies of the same object out of plastic. It consists of two parts: the mold itself and the injection machine. Plastic pellets are fed into the machine, where they are melted and injected into the mold under high pressure. The molten plastic then cools and hardens, taking on the shape of the mold cavity.

Single cavity molds are typically used for small objects such as toy figurines or bottle caps.

The main advantage of this type of mold is that it is relatively simple and inexpensive to produce.

Disadvantages of Single Cavity Mold

  • The mold can only produce a limited number of objects before replacing them.
  • The objects produced by a single cavity mold are usually not very precise and may have cosmetic defects such as surface imperfections or mismatched seams.
  • Single cavity molds are not well suited for mass production because only a tiny amount of plastic can be injected at once,
Multi-Cavity vs. Single Cavity


Multi-cavity injection molding is a plastic process that produces multiple parts from a single mold. The process commonly produces identical parts with high tolerances and low surface finish requirements.

Multi-cavity molds can have 2, 4, 8, 16, or more cavities, depending on the size and complexity of the part.

Advantages of multi-cavity molding

  • Multi-cavity mold increases production efficiency by reducing the cycle time for each part.
  • Multi-cavity molds typically have lower unit costs than single-cavity molds due to the increased number of parts produced from each mold.

Disadvantages of multi-cavity molding

  • Multi-cavity mold can be more challenging to design and manufacture than a single-cavity mold.
  • The increased number of cavities can result in more significant variation in the dimensions of the final parts.

Thus, careful consideration must be given to designing a multi-cavity mold to ensure the resulting parts meet the required specifications.

Family Mold

Family injection mold is a type of mold that contains multiple cavities, each of which is the same shape as the desired product. This allows for the efficient production of large quantities of identical items.

family mold

Advantages of family injection mold

  • Family injection mold eliminates the need for multiple molds, saving time and money.
  • Family injection molds often have shorter cycles than other types of molds, which means that products can be produced more quickly.

Disadvantages of family injection mold

  • Family injection molds are more expensive than some other types of molds.
  • The process can be complicated if a product requires a different color or material in each cavity.

Types Of Injection Molding Technology

  • Cube Molding
  • Die Casting
  • Gas-Assisted Injection Molding
  • Liquid Silicone Rubber Injection Molding
  • Metal Injection Molding
  • Micro Injection Molding
  • Reaction Injection Molding
  • Thin-Wall Injection Molding

CNCFIRST-Reliable Injection Molding Services Provider

CNCfirst is a leading provider of reliable injection molding services, committed to delivering exceptional quality and service to customers in various industries. We also provide mold design and manufacturing services.

Whether you need help with prototype development, short-run production, or large-scale manufacturing, we have the experience and expertise to deliver superior results every time.

With a commitment to precision, quality control, and customer satisfaction, we are the go-to choice for reliable injection molding services.

Contact us today to learn more about how to work together to create a successful product launch.


So there you have it- the three main types of injection molds and their respective advantages and disadvantages. Hopefully, this has given you an excellent overview of what to expect from each type of mold.

If you’re still unsure which mold would be best for your needs or need help finding a qualified manufacturer, don’t hesitate to visit our homepage. We’d be happy to help you find the perfect injection molding partner for your business. Thanks for reading!


What Is Injection Mold?

Injection mold is a process where molten plastic is injected into a mold to create various plastic products. The main advantage of injection molding is that it allows for the mass production of plastic products with little waste.

In addition, injection molding is relatively fast and inexpensive, making it a popular choice for manufacturing various plastic products.

What Is The Most Common Plastic Injection Molding Materials?

There are different types of plastic injection molding materials.

Acrylic (PMMA), acrylonitrile butadiene styrene (ABS), nylon polyamide (PA), polycarbonate (PC), polyethylene(PE), polyoxymethylene(POM), polypropylene(PP), polystyrene(PS), thermoplastic elastomer (TPE), thermoplastic polyurethane (TPU).