Are you trying to decide between using a hot runner mold or a cold runner mold for your manufacturing project? It can be difficult to choose, but it’s important to find the right solution for your specific application. In this blog post, we'll provide an in-depth comparison of hot and cold runner systems, explaining the advantages and disadvantages of each one in detail. Read on to learn more about how these two types of molds differ, so that you can make an informed decision as you plan out your next manufacturing endeavor!

Contents

1. What is a hot runner mold?

2. Structure of hot runner system

3. What are the benefits of using a hot runner mold?

4. What are the drawbacks of using a hot runner mold?

5. What is a cold runner mold?

6. What are the benefits of using a cold runner mold?

7. The difference between hot runner system and cold runner system.

8. Conclusion

What is a hot runner mold?

A hot runner mold is a mold that uses a heating device to keep the melt in the runner from solidifying at all times.

The hot runner is heated to ensure that the plastic in the runner and gate remains molten. Since there are heating rods and heating rings near or in the center of the runner, the entire runner from the outlet of the barrel to the gate of the injection molding machine is in a high temperature state, so that the plastic in the runner remains molten. In short, the hot runner is an extension of the barrel of the injection molding machine.

Structure of hot runner system

Hot runner system generally includes two types: open hot runner and needle valve hot runner.

Open type hot runner is generally composed of several parts such as injection nozzle, manifold, hot nozzle, temperature control box and accessories.

Needle-valve hot runner is generally composed of injection nozzle, manifold, hot nozzle, temperature control box, cylinder or oil cylinder, valve needle and accessories.

The nozzle form of hot runner is divided into large water mouth and pointed mouth.

The manifold is used in one mold with multiple cavities or multi-point feeding and single-point eccentric feeding. The size of the manifold is mainly determined by the distribution of cavities on the mold, nozzle arrangement and gate position.

The temperature control box includes the main unit, cables, connectors and wiring male and female sockets. Hot runner accessories usually include heaters and thermocouples, runner seals, connectors and junction boxes, etc. The main purpose is to control the temperature of manifolds and hot nozzles.

What are the benefits of using a hot runner mold?

The benefits of using a hot runner mold are numerous. First and foremost, by using a hot runner mold, you eliminate the need for runners and gates. This means that you can produce parts with much greater complexity and detail. Additionally, because there is no need for runners and gates, the flow of plastic is much more consistent, which leads to improved quality and consistency in your parts.

Another benefit of using a hot runner mold is that it allows you to produce parts with very thin walls. This is because the heat from the runners melts the plastic in the part's cavity so that it flows evenly and consistently. Thin-wall parts are often difficult to produce using traditional molds because of inconsistencies in the flow of plastic.

Finally, using a hot runner mold can also help to reduce cycle time and manufacturing costs. This is because there is no need for additional steps such as runner removal or gate cutting.

What are the drawbacks of using a hot runner mold?

Hot runner molds are a great way to avoid problems with cold shuts and other quality issues that can arise when the mold is opened, and the plastic is injected. However, they do have a few drawbacks.

The first is that they are more expensive than traditional molds. This is because they require additional hardware, such as heating elements, to keep the plastic in the runners hot.

Another downside is that they are more difficult to maintain. The heating elements must be kept clean and free of debris, or else the plastic will contaminate and produce poor-quality parts.

Finally, hot runner molds tend to wear out more quickly than traditional molds. This is because the repeated heating and cooling can cause the metal to expand and contract, leading to cracks and other damage.

What is a cold runner mold?

Cold runner is a molten plastic flow channel machined on the mold parting surface; the main purpose is to provide a channel for the molten resin to flow into the cavity through the gate. After entering the cavity, the molten resin cools and hardens, is ejected with the part, and the next injection cycle begins again.

What are the benefits of using a cold runner mold?

The first benefit of using a cold runner mold is that it is more accurate. With a hot runner mold, the resin can start to solidify before it reaches all of the cavities in the mold. This can cause problems with the quality of the parts that are produced. With a cold runner mold, the resin stays liquid until it reaches the cavities, which results in better quality parts.

Another benefit of using a cold runner mold is that it is more efficient. With a hot runner mold, there is often a lot of wasted resin because it solidifies in the runner and not in the cavities. This can be very wasteful and expensive. With a cold runner mold, there is no waste because the resin only goes where it is supposed to go.

Finally, a cold runner mold is easier to clean than a hot runner mold. With a hot runner mold, you have to wait for the resin to cool off before you can clean it. This can be dangerous if you are working with flammable resins. With a cold runner mold, you can clean it while it is still warm, which makes it much safer to use.

The difference between hot runner system and cold runner system.

A. Different references

1. Hot runner: It is a brand-new structure that the sprue and runner of traditional mold or three plate mold are heated, and it is not necessary to take out the runner and sprue at every molding.

2. Cold runner: After cooling down in the mold and taking out with the product, remove the cold material and trim the pouring day to get the final product with no obvious traces of pouring.

B. Different uses

1. Hot runner: Different plastic characteristics, shape, size, thickness, weight, cavity arrangement and gate position, there are several different shapes and sizes of hot nozzles and runner plates on the market to suit various products.

2. Cold runner: simple mold design, widely used.

C. Different characteristics

1. Hot runner: The plastic in the runner and gate is kept in molten state by means of heating. Since there are heating rods and heating rings near or in the center of the runner, the whole runner from the nozzle outlet to the gate of the injection molding machine is in a high temperature state, so that the plastic in the runner is kept molten, and it is generally not necessary to open the runner to take out the condensed material after shutdown.

2. Cold runner: The cold material produced needs to be crushed and recycled again.

Conclusion

If you are in the process of designing a mold for your plastics products, you will need to decide between a hot runner mold or a cold runner mold. Hot runner molds have several benefits, such as reduced material waste and increased productivity. However, they also have some drawbacks, such as higher initial costs. Cold runner molds are less expensive upfront, but they may not be as efficient in the long run. Ultimately, the best type of mold for your business will depend on your specific needs and goals. To learn more about hot runner molds and cold runner molds, read our other blog post here.