April 2, 2024

Hot Runner Systems in the Injection Molding Process

hot runner system

Introduction to Hot Runner System

The injection molding industry is full of various innovative solutions. One of them is the hot runner system which has been widely recognized as a significant breakthrough. It not only modifies the way we produce and apply plastic, but also affects the whole plastic production process. A hot runner system, on the other hand, can be defined as a set of heated parts. Through this process, the parts are poured into the mold’s cavities. These technologies are the basis of the modern manufacturing process. It is a great way that plastic can be made more effective, better quality and cheaper.

The birth of the hot runner technology started in the mid of the 20th century. After it came into being, it has had a significant impact on the sphere of injection molding. It has done this in two ways: firstly, it has allowed for more detailed designs, and secondly, it has reduced waste.

It has been observed that the hot runner systems have continued to improve. They pay attention to being exact and to being environmentally friendly in the production of their products. These systems are capable of maintaining the molten state of the plastic. Hence, there’s no need to process and recycle any leftover pieces. This brings about the production of more things at a lesser cost. Hot runner technology has made it possible to implement the injection molding process in a seamless and efficient manner. It gives designers and producers a new playing field to experiment on. The history of continual changes and upgrades in this industry represents the industry of injection molding, which is always on the go. The latest technologies are the factors that make companies think and help them to do more.

hot runner system

Types of Hot Runner Systems

Open Hot Runner Systems

Open hot runner systems take molten plastic from the injection molding machine and put it straight into the mold cavity. They are perfect for making a lot of products where keeping things simple and reliable is important. The plastic flows freely, which means they work well for items that don’t need a lot of detail. Benefits include:

  • Less waste of materials. There’s no unused cold runner to throw away.
  • Quicker production times, which is great for making lots of items.

They’re used for items we use every day like containers and toys. Mentioning mold cavities, final product, and injection molding machines shows how effective open hot runner systems are at making strong products from raw materials.

Valve Gated Hot Runner Systems

Valve gated hot runner systems are more advanced. They control how plastic goes into each mold cavity with a valve. This method is good for:

  • Precise control, allowing for more complex shapes.
  • Making high-quality items with fewer flaws.

They are best for detailed projects like car parts and medical gear. These systems meet the high standards needed for hot runner mold work, making sure every item is just right.

Sprue Gate Hot Runner Systems

Sprue gate hot runner systems have one big gate that lets molten plastic in. They find a middle ground between open and valve gated systems by offering:

  • Good flow control, good for many kinds of products.
  • More efficient use of plastic material, creating less waste than older methods.

You’ll find them in things like home appliances and toys that need to look good but are not too complex. Using keywords like mass production and mold cavity points out the sprue gate system’s ability to make a wide range of good-quality items efficiently.

Together, these hot runner systems show how makers use new techniques to mold plastic. They aim to use materials well, make precise items, and work efficiently.

hot runner system

The Core Components of a Hot Runner System

Understanding the Manifold in Hot Runner Systems

In hot runner systems, the manifold is key. It sends molten plastic into the mold cavities. It works like a heated path. This ensures that the plastic flows smoothly into each cavity. Manifolds come in different types, like standard and insulated. Each type meets different needs. A standard manifold heats up directly. This makes sure the plastic flows evenly. This is great for many injection molding jobs. An insulated manifold, on the other hand, keeps the heat in. This means you get even better control of the flow. This is really useful for big injection molding projects.

Choosing between these types depends on a few things. These include the type of plastic you’re using and how you want the final product to look. A well-thought-out manifold system precisely directs the molten plastic. This means products are made quickly and rarely have any flaws. This shows just how important a good manifold system is for high-quality results in injection molding.

The Role of Nozzles in Hot Runner Efficiency

In the world of injection molding, the nozzle is very important. It has the key job of moving the molten plastic from the machine into the mold cavities. There are many kinds of nozzles. Each kind is made for a different job. This makes hot runner systems more flexible and efficient.

For instance, open nozzles let plastic flow all the time. This is good for easy jobs that don’t need perfect precision. Valve-type nozzles, though, give more control. They open and close at just the right times. So, they are better for making complex or high-quality items. Gate-type nozzles match with certain mold layouts. They make sure the plastic goes straight into the cavities without losing much pressure. This helps make every product of the same high quality.

By guiding the plastic right, the hot runner nozzle helps a lot in making high-quality parts. Understanding the different types of molding machine nozzles and what they do shows why it’s important to pick the right nozzle. Doing so makes sure the plastic injection molding system works the best it can.

Heater Technologies: Ensuring Optimal Performance

Heater technologies in hot runner systems are vital for providing a sufficient temperature throughout the system and to its perfection for molding, regardless of ambient temperatures. Heaters differ when it comes to the heat principle, for example, band heaters and cartridge heaters use different ways to generate heat. The heater can be connected around the pipe body as a spiral tube or may be placed in the holes located on the walls of the cartridge of the cooler.

Choosing the right heater tends to require deliberation on various crucial points. And among these are the minimal temperature needed, maximum power consumption that the heater can provide, and how uniform the heat distribution has to be. Another important thing is temperature management as well. Controlling temperature secures the melt flow is stable, which has an immediate impact on the material properties, the print resolution, and the core requisite of producing high-quality parts.

For peak performance, an ongoing check on the heated manifold temperature (considering the cavity orientation) and the adjustment thereupon have to be done. The specified temperature control and continuous monitoring allow this system to maintain its highest level of performance, such that the plastic is moldable at its best.

hot runner system

How does a Hot Runner System Work?

A hot runner system acts like a sophisticated channel. It moves molten plastic from an injection molding machine into the mold cavities. This system makes sure the molded parts are consistent and of high quality. The process starts with melting plastic pellets into liquid. This liquid plastic is then pushed through the system from the injection points. A key feature of the hot runner system is keeping the plastic melted. Heated parts like manifolds and nozzles stop the plastic from cooling down too soon.

Next, the liquid plastic goes through the valve gate. The valve gate is very important. It controls the flow of the molten plastic into the mold cavities very precisely. This careful control means the final part is filled evenly. This reduces mistakes and makes the product better overall. The smooth flow and exact control from the valve gates show why a good hot runner injection molding system is critical for making things today.

The heated manifold is central to this process. It sends the molten plastic to all the right injection points. The manifold makes sure the temperature and flow are even. This is crucial for making the final part. As the plastic fills the mold cavities, it starts to cool and harden. This forms the desired molded part. By managing the plastic’s temperature and flow well, the hot runner system ensures the final parts are of high precision and high quality, ready to be used.

Hot Runner Systems vs. Cold Runner Systems

Two key methods of injection molding are the hot runner system and the cold runner system, which have their own definition and working principles. A hot runner system uses heated components to keep the plastic molten during its travel from the injection molding machine to the mold cavities, which thereby eliminates solid runners and decreases plastic waste significantly. However, the cold runner system enables the plastic to cool and solidify in the runners, hence the runners need to be ejected together with the part, hence the waste of plastic.

The advantages of hot runner systems over cold runner systems are numerous. Firstly, the encapsulated runner in a hot runner system drastically reduces the energy consumption as it maintains the melt’s temperature and does not require extra heating. This is to say that the process becomes more efficient, which is very important in the high volume production. In addition, the non-existence of solidified runners in hot runner systems implies that there is no need for a cooling mechanism to cool down the runners thus enhancing the production process. In the end, the reduction in plastic waste not only makes the hot runner system more eco-friendly but also more cost-effective in the long term, as every bit of plastic will be used in the final product.

FeatureHot Runner SystemCold Runner System
Plastic StateKeeps plastic molten during transitAllows plastic to cool and solidify in runners
RunnersEliminates solid runners, reducing wasteRunners solidify and need to be ejected, increasing waste
Energy ConsumptionLower, due to encapsulated runners maintaining temperature without extra heatingHigher, due to reheating and cooling processes involved
EfficiencyIncreased in high volume production due to continuous flowPotentially reduced due to additional steps for runner ejection and recycling
Cooling MechanismNot required for runners; focuses on the final product, speeding up processRequired to cool down the solidified runners, adding to cycle time
Eco-friendlinessMore eco-friendly; reduces plastic wasteLess eco-friendly; produces more waste
Cost-effectivenessMore cost-effective in the long-term; utilizes all plastic materialLess cost-effective; additional costs for runner handling and material waste
Ideal ApplicationsHigh volume production, complex parts needing precise temperature controlLow to medium volume production, simpler parts, or varying color/material runs

When to Choose Hot Runner Systems Over Cold Runner Mold?

The decision of the hot runner system or the cold runner comes down to a few main factors. If the project is aimed at such a high production efficiency, which is particularly needed in the area of complex parts, the hot runner system becomes the best choice. It is characterized by a high level of temperature control, which plays a vital role in ensuring the quality of shapes that are difficult to replicate. Furthermore, this system has an advantage in cases where plastic waste and energy consumption as the major concerns. Through a hot runner system, the cooling time is cut down and the efficiency is increased. Therefore, it stands out, especially for big volume injection molding projects that produce innumerable plastic parts.

Nonetheless, it should also be noted that hot runner systems are not perfect in all scenarios. They are almost always pricier in the beginning and need to be monitored and taken care of in a strategic manner. Assessing the need for a hot runner system could be a significant option if the manufacturing process includes parts with different color demands or generally low volume. At the end, a decision on the choice of a hot or cold runner system should be based on a comprehensive analysis of the corresponding production characteristics, taking into account quality, efficiency, and cost issues.

So, if you’re a custom injection molder looking for a good investment, ACO Mold is an excellent choice. We specializes in making injection molds. They provide a full range of services, from creating the mold to producing the final product. ACO Mold works with many industries. This includes things like consumer electronics, household items, cars, medical devices, and farming equipment. We send custom molds and products to more than 20 countries. Their many years of experience mean they really understand how to make molds. We also know a lot about international standards like HASCO and DME. Choosing ACO Mold means you get a skilled partner who knows how to handle the detailed work of custom injection molding.

hot runner system

Advantages of Hot Runner Systems Explained

Cycle Time Reduction and Increased Productivity

In the case of hot runner systems, there are some major advantages that come into play during the injection molding process and help in increasing the production efficiency. This is demonstrated by the shortening of the cycle time, that directly results in the increased productivity. This system is realized by preserving a molten state of the plastic, thus refraining from the need for the material to be re-heated. This will result in the plastic being injected into the mold cavity faster and, thus, the final product being produced faster. Such cases can be considered to be under the category of heavy injection molding projects where time is very important.

Material Savings and Waste Reduction

Besides, this system helps in material savings and reduction of waste. In contrast to the conventional cold runners where the cold sprue and runners are discarded after every cycle, hot runner systems are not prone to this type of waste as the plastic stays in its molten state within internal channels. Besides the fact that it is a way of reducing the amount of plastics generated, it also costs less to purchase materials and energy, which makes it more cost-effective and environmentally friendly.

Improved Part Quality and Consistency

Aside from economic advantages, hot runner systems also have huge yield quality and uniformity of the part. The accurate temperature control and better flow control reduce the chance of defects such as sink marks and weld lines, which are often found in parts made by using the cold runner systems. With this method, each part has the accurate dimensionality and achieves the color requirements as well as the quality standards as of the finished product. Consequently, hot runner systems are a great alternative for those companies that aim to improve the safety, quality, and efficiency of plastic injection molds.

Why Are Hot Runner Systems A Good Investment For Custom Injection Molders?

If you need the molding of injection-molded parts, the advantages of hot runner systems are many. For example, additive manufacturing systems give you very precise sizes of the custom parts.This is very important. They do this by the use of a precise regulation of temperature. This allows for all aspects to be kept uniform, which includes even the most intricate shapes and designs.

Another plus is that not all hot runner systems let the plastic stay in the machine for a long time. It helps in obtaining the materials in the right condition, and thus the final products are always of high quality. Together, hot runner systems give the users the benefits of accuracy, efficiency, and control of the quality. They are a fit for custom injection molders who want to meet the needs of customers, but also to develop their production process.

hot runner system

Applications of Hot Runner Systems in Custom Injection Molding

Automotive Sector

In the automotive industry, hot runner systems are the reason that injection molding of parts is revolutionizing. These systems help in the production of more accurate parts, which can be fabricated into complex shapes such as dashboard components and lighting fixtures. Hot runner systems’ ability to achieve precision consequently leads to parts that satisfy the strict requirements that are set in the automotive sector.

Medical Device Production

The medical device manufacturing industry is to a large extent dependent on the supply of high-quality and precisely manufactured components. Hot runner technologies help in the manufacturing of crucial components such as surgical tools and diagnostic equipment covers. The system’s ability to precisely manufacture parts with little or no waste has enabled it to be the go-to tool in this field.

Electronic Components Manufacturing

When it comes to the manufacturing of electronics components, where every millimeter is a critical part of the whole, the hot runner systems provide the precision needed for detailing the intricate parts such as connectors and switches. The systems’ insulated runners guarantee that every finished part has an identical appearance and will be in compliance with the consumer goods specifications, which in turn makes for more functional and reliable electronic devices.


Hot runner systems, as their name implies are used for the production of the plastic packaging material, including bottle caps, and containers. Such systems provide for the high-volume production while still delivering on the need for quality and consistency that is important for consumer goods. The speed and the low-waste nature of hot runner systems ensure them as the favorites for making of some more parts within the packaging industry, which in turn contributes to more environmentally friendly manufacturing practices.


Hot runner systems have revolutionized the injection molding process, providing unparalleled efficiency, waste reduction, and quality control. From their humble beginnings to their critical role in modern manufacturing across various industries, these systems represent a perfect blend of innovation, precision, and environmental responsibility. Whether you’re a seasoned manufacturer or simply someone curious about how the goods around us are made, one thing is clear: hot runner systems are integral to creating the high-quality, consistent products we rely on every day.

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