The two predominant categories of plastic injection molding are cold runner systems and hot runner systems. Each type of plastic molding comes with its own distinct benefits, depending on the part or component you want to create through the process. That is why it’s important to know the difference between these two manufacturing methods before hiring a plastic injection molding company to design and produce your parts. 

What are the differences between hot and cold runner molds?

Before hiring a company for plastic injection molding, you should have a deeper understanding of the differences between cold and hot runner molds. This will allow you to have an informed and more productive discussion before determining the best option for your requirements. 

Cold runner molds

Cold runner molds generally consist of either two or three separate plates within the base of the mold. Molten thermoplastic gets injected via a nozzle and the sprue, and it fills an entire runner network leading to mold cavities. This system features unheated runners that distribute the plastic into individual molding cavities. This system then cools down the sprue, the runner, and the gate together with the part being molded. 

  • Two-plate cold runner molds: In this type of cold runner mold, both the runner and the sprue remain connected to the finalized product. The process utilizes an ejection system to separate these parts from the final component. 
  • Three-plate cold runner molds: Here, a stripper plate is used to contain the sprue that delivers the required amount of molten thermoplastic. This system separates runners from the molds as they open. 

Hot runner molds

Hot runner molds have two plates that receive the necessary heat from the manifold system. This system maintains consistency by keeping both the heating cylinder and the plastic at the same temperature. 

Here, the heated runner has a separate plate housing which is stationary throughout the process. When the molding plate opens, the final product is without an attached runner.

Although there are many different types of systems that utilize hot runner molds, the two main categories are internally heated and externally heated. The former are ideal for polymers sensitive to variations in temperature, while the latter provide enhanced flow control. 

What are the advantages of each type of mold?

Both cold runner and hot runner molds have their own production benefits that make each type of molding suitable for different applications. Let’s see what the biggest advantages of these two processes are: 

  • Benefits of cold runner molds: Cold runner molds are a good options because of these characteristics:
    • Very high cost-effectiveness
    • Low maintenance costs
    • Suitable for a wide array of engineered and commodity thermoplastics 
    • Exceptional process flexibility
    • Accommodates quick design changes
  • Benefits of hot runner molds: Hot runner molds are a great choice because of the following qualities: 
    • Very fast cycle times
    • Fewer number of necessary post-production activities and lower production costs
    • Reduced post-production waste
    • No need for robotics for runner removal
    • More efficient mold automation process

What is the most reputable plastic injection company to partner with?

Cold runner and hot runner molds are only one component of the plastic injection molding process you should be familiar with. First, you should find out more about the most important terms of plastic injection molding and learn what the most common types of plastic molding methods are. Only then is it time to explore all the different components you can manufacture with plastic injection molding and choose the best process for you. 

You can also shorten your search and immediately outsource your plastic injection molding to Wunder Mold – a reliable manufacturer of high-quality plastic parts and components per your exact specifications. We choose the best resin, design a precise part and cost-effective manufacturing process, and bring you the items your business needs. Give us a call at (707) 448-2349, or send an email to