Hot Runner vs. Cold Runner Molds: A Comprehensive Comparison
October 13, 2023
In plastic injection molding, precision and efficiency are paramount. One critical aspect is choosing between hot and cold runner molds. In this article, we’ll delve into the intricacies of both. We will also explore their definitions, functionalities, advantages, and disadvantages.
What is a Hot Runner Mold?
A hot runner mold is a plastic injection molding system in which the heated plastic is injected into multiple cavities together. The molten material is directed by a series of channels and valves known as ‘runners,’ ultimately forming the desired shape.
During production, all hot runner components are kept at a constant temperature. It ensures an optimal flow of molten plastic and a higher-quality final product. Furthermore, hot runner molds can process thermally sensitive materials. It results in lower degradation due to their temperature control systems.
Hot Runner System Definition and How It Works
A hot runner system comprises heated tips, runners, gates, and cavities. These components are heated by an injection machine or auxiliary heating system. The molten plastic is channeled through the heated runners. Then, it enters the individual cavities, which cool down before being ejected as a finished product.
There is no need to switch between molds during production cycles; this results in faster cycle times and improved efficiency. All components remain hot throughout production. A hot runner system also allows individual temperature control in each component. It allows for better flexibility and precision.
We put a video below to compare the working process of the hot runner system and cold runner system for better understanding. Please continue reading.
Advantages of Hot Runner Molds
The primary advantage of a hot runner mold is its improved efficiency. It occurs by eliminating the need to switch between molds during production. Hot runner systems also enable higher productivity due to faster cycle times and lower labor costs.
In addition, hot runner molds can process thermally sensitive materials without wearing out. It makes them ideal for working with polymers such as polyvinyl chloride. Finally, a hot runner system allows individual temperature control of each component in the mold. It results in better precision and accuracy.
Disadvantages of Hot Runner Molds
The primary disadvantage of a hot runner mold is its higher cost. Hot runner molds require a more complex setup. They also need additional components such as heaters, sensors, and temperature controllers that may drive up production costs.
Furthermore, their complex design makes hot runner systems more difficult to maintain. Finally, they’re not ideal for working with materials sensitive to thermal degradation or with low melting points.
What is a Cold Runner Mold?
A cold runner mold is a type of injection molding technology that does not use any heated components. Instead, it uses channels to direct the molten plastic from the injection point into the cavity, which cools and solidifies.
In some cases, there may be more than one channel where the molten plastic can flow, producing multiple parts or shapes from a single mold. Cold runner molds can be used in low-volume or high-volume production, depending on the parts’ complexity.
Cold Runner System Definition and How It Works
A cold runner mold is an injection molding process. During this, the channels that guide molten plastic from the injection point to the cavity are not heated or thermally managed. This causes the molten plastic to cool quickly, resulting in a solidified part in less time than with heated-runner systems.
Cold runner molds can be used for both low-volume and high-volume production, depending on the complexity of the design. In a cold runner mold setup, molten plastic is pumped into the open end of a channel, which usually consists of two or more paths leading to the cavity. The runners are then directed around any internal obstacles and out of the park. After all of the plastic has been injected, the runners are disconnected from the mold cavity and recycled.
Advantages of Cold Runner Molds
The main advantages of cold runner molds include lower energy costs, faster production time, better control over part dimensions, and easier maintenance compared to similar hot runner systems.
Cold runner molds also require less complex equipment, resulting in a shorter setup time and lower production costs. In addition, cold runner molds are better suited for producing parts with intricate details or complex shapes. This is because the plastic cools more quickly than it does in hot runners.
Disadvantages of Cold Runner Molds
The main disadvantages of cold runner molds include a lack of control over material flow and a tendency to produce more flash than hot runner systems. Additionally, cold runners cannot handle thermosensitive materials. This includes certain types of plastics because the material may harden before exiting the mold.
Finally, the shorter cycle time of cold runners can lead to increased wear on molds over time due to the higher frequency of use. This means that they will need to be replaced more often than hot runners. Hence, cold runner molds may offer advantages in certain areas. However, it is important to consider the full scope of their benefits and drawbacks before investing.
Here is video to compare the hot runner and cold runner system.
Comparison between Hot Runner and Cold Runner Molds
Regarding injection molding, there are two main methods of runner systems – hot runner and cold runner. Both approaches offer certain benefits and drawbacks. So, weighing each option is important to determine which is best for your project.
Cost
The cost of a hot runner system is usually higher than a cold runner system, as it tends to require more complex systems and components. However, hot runner systems use fewer materials, which reduces costs when produced in large volumes. Cold runners tend to have lower initial setup costs but require more material, depending on the circumstances.
Cycle Time
Hot runner systems typically offer faster cycle times than cold runners. This is because they reduced the need for material changes and assembly between cycles. This can help reduce the lead times of projects, particularly when producing large volumes of parts. Cold runners may be more suitable in certain small-volume scenarios where setup costs are more easily managed.
Volume
Hot runner systems are usually preferred for large-scale projects. They reduce materials usage and cycle times. This makes it a cost-effective choice when high volumes are required, as less material is wasted in the process. Cold runners can be more suitable for smaller batches where setup costs may not outweigh the benefit of a hot runner system.
Materials Usage
Hot runner systems offer the ability to reduce materials usage compared to cold runners. This is achieved by eliminating the sprue and runner that are necessary with traditional cold runners. It results in less material wastage. Cost savings can be significant for large-scale projects, making it an attractive option if the initial setup costs are manageable.
Complexity
Hot runner systems tend to be more complex than cold runners. They require additional components and precision engineering for effective operation. This can make them ideal for complex parts that would otherwise need multiple setups with a traditional cold runner system. However, they may not be suitable if the project has limited resources or time constraints. Cold runners are more straightforward and require less setup in comparison.
Choosing a Hot Runner System: Factors to Consider
When you are considering what hot runner system to choose, there are a few factors that you need to consider.
Injection Pressure
Injection pressure is the first factor that should be taken into consideration. Ensuring that your hot runner system’s injection pressure will support the plastic resins in your production process is important. This will ensure that all parts of your production are made with the highest quality.
Heating
The next factor to consider is heating. Hot runner systems use various types of heaters, such as electric or hot oil. These will need to be carefully chosen. Why? Because it ensures that the system can withstand the high temperatures required for certain plastic resins. In addition, you should also consider how quickly these heaters can be controlled. This will provide the most efficient production process.
Gate Type
The gate type you choose is another factor that must be considered when choosing your hot runner system. Various types of gates are available, such as edge, fan, and pin gates, and each has its benefits depending on your specific needs. Be sure to research which type will be best for your production process.
Standard or Custom-Made System
When selecting a hot runner system, you must decide whether you want a standard or custom-made system. A standard system is usually more cost-effective, but it may not meet all of your requirements in terms of design and performance. On the other hand, a custom-made system can provide you with exactly what you need, but it may come with a higher price tag.
Types of Plastic Processing
Another important factor to consider when selecting your hot runner system is the types of plastic processing you intend to use. Different resins will require different levels of heat. This is required to process them correctly, which should be considered when choosing the system.
Runner Size
You should also consider the size of the runner that is needed for your production process.
Multi-Zone Temperature Control
Finally, you should consider the type of multi-zone temperature control. It is needed to ensure consistent processing of plastic resins. Different types of hot runner systems can provide different levels of temperature control. So, it is important to find one that meets your specific needs. By considering all of these factors, you can ensure that you are selecting the best hot runner system for your production process.
Choosing a Cold Runner System: Factors to Consider
It is critical to decide whether a cold or hot runner system is best for your needs. For example, consider production volume, product complexity, and cycle times when selecting a runner system.
Nozzles
Nozzles are the crucial connection between the injection molding machine and the mold. So, choose one compatible with your specific model of machine and application.
Nozzle Tips
Nozzle tips come in different sizes and shapes depending on the needs of your application. Consider aspects such as channel lengths, material throughput, and cooling requirements when selecting the right nozzles for your runner system.
Runner Manifolds
Runner manifolds are the paths that distribute molten plastic from the nozzle to cavities in the mold. It’s important to select a design with enough flexibility and accuracy. It will help distribute the material throughout the entire cavity evenly.
Piston Assemblies
Piston assemblies are also crucial components of cold runner systems. This is because they ensure that material is pushed through the correct channels. So, when selecting a cold runner system, be sure to pay attention to the size and shape of your piston assembly for optimum performance.
Pneumatic Connections
Finally, it’s important to consider the pneumatic connections necessary for a cold runner system. These include fittings, valves, and regulators that ensure accurate pressure control throughout the injection molding cycle. Choose components that are compatible with your injection molding machine for the best results.
Selecting the right cold runner system requires careful consideration of all these factors to ensure successful production. Doing your research now can save you a lot of time and money down the road!
Conclusion
Hot and cold runners have distinct advantages. The former are ideal for large-scale production runs due to their cost efficiency and strong injection consistency. On the other hand, cold runner molds require little maintenance. But they can be more expensive upfront, depending on the mold size.
No matter which option is chosen, it’s important to ensure the right process and materials are chosen. Working with an experienced partner who can guide you through this process will ensure you get the best results for your circumstances.
