Hot Runner vs Cold Runner Injection Molding

Hot Runner vs Cold Runner Injection Molding

Hot runner vs cold runner injection molding

Modern manufacturing industries use injection molding to produce various plastic products for daily use. It’s a process that brings imagination to life, transforming raw plastic materials into intricate shapes, from toy figurines to automobile parts.

However, what makes injection molding truly fascinating is its precision and versatility. At the heart of this precision lie two critical methods: hot runner and cold runner injection molding. These methods are essential in the manufacturing industry and are crucial in producing various plastic components.

This article explores the differences between the two main types of runners used in injection molding: hot and cold.

What is hot runner and cold runner injection molding?

Hot runner and cold runner injection molding are two distinct techniques for manufacturing plastic parts. They differ in how they manage the flow of molten plastic into molds and handle runner systems.

  • Hot runner injection moulding:

Industrialists use hot runner injection molding with the help of a hot runner system, where molten plastic is poured from the machine to the mold cavities. The temperature of this system is kept high to keep the plastic in the molten state. 

This is achieved by using a set of heaters and controllers to maintain the runner’s temperature. The key benefit of the hot runner system is that it does not let the plastic material get hard. It is molten, thus elevating us to eliminate extra discharge after every cycle.

Hot Runner Injection Molding

Hot Runner Injection Molding

  • Cold runner injection molding:

During this technique, the runner system is kept at room temperature. Unlike hot runner systems, where the plastic in the runners remains molten, cold runner systems allow the plastic to cool and solidify within the runners after each cycle. 

This solidified material is then typically discarded as waste. Cold runner systems are simpler and cost-effective but can generate more material waste than hot runners.

The primary distinction between these two methods lies in how they manage the temperature of the runner system and handle material waste. In the hot runner system, the temperature is high to keep the product in a molten state, while in the cold runner system, the temperature is kept low. 

You get more waste in the cold runner system than in the hot runner system. The choice between these methods depends on the specific requirements and priorities of a given injection molding project.

Did you know?

The concept of hot runner injection molding dates back to the early 80s, making it a technology with a long history of development. However, it wasn’t until the 21st century that hot runner systems were commercially introduced and widely adopted in the manufacturing industry.

Hot runner vs Cold runner injection molding: 

If you want to make the right choice between hot or cold runner systems, you need to understand the differences. Let’s explore some of them.

  • Temperature requirements:

Runner system: The runner system remains at a high temperature throughout the hot runner injection molding cycle. This ensures that the plastic material doesn’t solidify within the runners, allowing for reduced material waste and faster cycle times.

Cold runner: Conversely, cold runner injection molding employs unheated runners at room temperature. As a result, any excess plastic material within these runners solidifies and is typically discarded as waste.

  • Material wastage:

Hot runner: Hot runner systems excel in reducing material waste. Because the runners remain hot, there’s minimal waste generated from solidified plastic material within the runners.

Cold runner: This system generates more material waste because the plastic in the runner solidifies. This can result in increased material costs and waste management.

  • Part quality:

Hot runner: Hot runner systems contribute to enhanced part quality with fewer defects. The consistent temperature in the runner system helps achieve uniformity in the final product, meeting tight tolerances and specifications.

Read more: Applications Of Hot Runner Technology

Cold runner: Achieving consistent part quality with cold runner systems can be more challenging. This is because the moulding product gets hard or solidifies in the runners.

  • Cycle time:

Hot runner: Hot runner systems can significantly reduce cycle times compared to cold runners. Production becomes more efficient since there’s no need to wait for the runners to cool down and solidify before ejecting the parts.

Cold runner: Cold runner systems generally have longer cycle times due to the cooling and solidification of the runners. This can impact production efficiency, especially for high-volume manufacturing.

  • Initial cost and Complexity:

Hot Runner: Setting up a hot runner system can be more expensive due to the need for specialized components like heaters and controllers. Additionally, the design of hot runner systems can be intricate, requiring careful engineering and customization for each project.

Cold Runner: Cold runner systems are simpler and more cost-effective to set up. They are often the preferred choice for smaller production runs and budget-conscious projects. They also have lower maintenance requirements compared to hot runner systems.

  • Material compatibility:

Hot Runner: Hot runner systems may not be suitable for all plastic materials, especially heat-sensitive ones. Some materials may experience degradation when subjected to the high temperatures required for hot runner molding.

Material compatibility

Material compatibility

Cold Runner: Cold runner injection molding can accommodate a wider range of plastic materials, including heat-sensitive ones. This makes it a more versatile option for projects with diverse material requirements.

The automotive industry has been a major driver of hot runner injection molding. It is commonly used for producing precision parts such as automotive interior components, bumpers, and dashboard elements. 

However, cold runner systems are often preferred when working with a wide range of plastic materials, including heat-sensitive ones. This versatility has contributed to their continued use in various industries.


In conclusion, if you want your business to be successful, you need to make the right choice about the runners. The decision should be guided by your project’s unique demands, budget constraints, and material specifications.

If you’re seeking expert guidance and services for both hot runner and cold runner injection molding, look no further than Go4Mould. As a trusted provider in the industry, we offer a wide range of plastic injection molding solutions tailored to your project’s unique needs. 

Contact us today and explore products that perfectly match your objectives, ensuring efficiency, cost-effectiveness, and superior product quality.

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