Comparing Hot Runner Systems with Cold Runner Systems

Hot and cold runner systems are two prominent names in the injection molding industry. These systems help produce plastic components via popular methods for pilot runs, low-volume production, and prototyping of designs. If you plan on investing in one of these systems but are wondering which one you should choose, we have covered you in this ultimate guide.

In it, we will dive deeper into what these systems are and their pros and cons. So, without any further ado, let's begin exploring!

What’s a Hot Runner System?

Hot runner systems were first manufactured by Mold-Masters Ltd in 1963. Since then, these systems have been seen as leading alternatives for cold runners. Deep down, a hot runner system is specifically designed to utilize manifolds as heating elements. It features two plates and gets heated along with molten thermoplastic.

As the molten plastic flows through the runner into the nozzle, the manifold ensures temperature control between the heating cylinder and the runner. The nozzle fills the mold cavity, and later, the molded plastic is ejected from the runner.

Pros of Hot Runner Systems

Following are some key advantages of hot running systems:

Cost-Effective: Though hot runner systems have higher starting costs, these are more cost-effective in the long run. All thanks to the quicker time cycles, decreased waste production, and improved part quality.

Swift Cycle Time: Cycle time refers to the time taken to complete one cycle of the molding process. With hot runners, you can eliminate the need to cool down the runner, reducing cycle time and increasing the overall efficiency of the system.

More Precision: Parts manufactured with hot runner molds are much more precise in their dimensions. This preciseness increases client satisfaction, helping industries produce top-tier products in reduced time cycles. So, why not kill two birds with one stone?

Flexibility in Mold Designs: Hot runner systems don't need a separate runner channel to distribute molten plastic directly into the mold cavity. They rely on a manifold for this purpose, which reduces waste production and cycle time.

Automated Injection Molding: Automated injection molding involves the use of machines and equipment to automate multiple stages of injection molding. This reduces the reliance on manpower, eliminating human errors and labor costs and improving production efficiency to a great extent.

Cons of Hot Runner Systems

Let’s now have a look at the cons of choosing hot runner systems over cold ones!

Higher Initial Setup Cost: The hot runner system requires more complex and additional components than that of cold runner systems. So, expect the initial setup cost to be higher.

High-End Equipment Required: You might not be able to access the high-end equipment used in hot runner systems. This can elevate the overall system's setup cost even more.

What’s a Cold Runner System?

Unlike hot runner systems, cold running molds utilize unheated runners to transmit molten thermoplastic to mold cavities via a nozzle. The main components of cold running molds include three plates, the number of which may vary depending on the design. When the entire process is completed, the runner comes out with the molded part. This type of molding system is sometimes preferred over hot running systems for its low setup and maintenance costs.

Pros of Cold Runner Systems

Let’s now hop onto the different perks one can experience with cold runner systems in injection molding.

Minimal Inspection and Maintenance: A cold runner features a simple channel connecting the injection molding nozzle to the cavities. It’s ejected along with the part, so there isn't any need to remove and clean it between molding cycles. Hot runners have a quiet, complex structure with temperature controllers, manifolds, and nozzles, making maintenance and inspection difficult.

Ideal for Thermally Sensitive Polymers: As the name indicates, hot runner systems work in high temperatures, making them less suitable for thermally sensitive polymers. That’s where cold runners come to save the day. Some of the thermally unstable polymers include engineering plastics, whose properties might get affected in high temperature.

Lower Investment Costs: Cold runner has fewer components than hot runner. There aren’t any advanced components that aren’t easily available, nor does the channel have a complex structure, making setup difficult. So, the investment cost is lower.

Faster Design Changes: As cold runners have simple structures, they can quickly accommodate design changes. This makes them more flexible than competitors since runner and gate locations can be easily changed or upgraded.

Easier Color Changes: Color changes are much faster and easier in cold runner systems, as there isn’t any risk of being left behind molten material. However, hot runner systems might make this task difficult with left behind molten materials, making the color different than it should be.

Cons of Cold Runner Systems

Here is a closer look at the different cons of cold runner systems:

Slower Cycle Time: These systems need longer cooling times to solidify plastic materials in the runner before the part is ejected. This increases the overall cycle time, making cold runners less efficient and costly in the long run. Some injection molding industries deal with this issue with specialized cooling techniques, like conformal cooling.

Material Wastage: In cold runner systems, the runner is necessary for delivering molten plastic to the mold cavity via a nozzle. The runner material, which matches the part being molded, cools and solidifies during the injection process. This solidification leads to material waste that needs to be removed and recycled, ultimately increasing material costs.

Factors to Consider When Making a Choice Between Cold and Hot Runner Systems

By now, you have explored the basic overview, pros, and cons of hot runner and cold runner systems. Let’s now dig deeper into the different aspects that make one stand out over the other and in which situations you should use each of them.

Part Complexity: If you plan on manufacturing complex parts with intricate details, you must choose hot runner systems. They can easily fill complex geometric cavities without leaving any bubbles. On the other hand, cold cunner systems are better for manufacturing simpler parts with fewer cavities to be filled.

Material Requirement: Cold runner systems prove helpful when dealing with thermally unstable polymers. Hot runner systems can be used to process a broad range of materials, but they are becoming an ideal fit for customized plastic injection molding projects. These projects often require dealing with specific materials that are sensitive to temperature changes.

Production Volume: As mentioned earlier, hot runner systems have faster molding cycles, as they skip a few processes that are a must in cold runner systems. This makes them efficient investments for increasing production volume. On the other hand, cold runner systems are perfect for lower-volume production runs, where the reduced waste from runner systems can compensate for longer cycle times.

Cost: Another important factor to consider is cost. Cold-runner systems tend to have lower initial investment costs than competitors, making them more attractive to cost-sensitive consumers. However, they forget to foresee cost comparisons in the long run. This is because longer cycle times and material wastage in cold-runner systems increase the overall production cost more than that with hot runners.

Maintenance Requirements: If you prefer lower maintenance costs, you should go with cold-runner systems. They have a simplified structure, whereas hot runners have a complex structure with heightened maintenance costs.

Where Can You Get the Best Hot Runner Systems?

If you are tempted by the perks of hot runner systems, wander no more and hop onto the CHRS website to score one. This amazing company has been manufacturing top-tier products for years now with the objective of offering their customers the best quality and services. Their product range is also diverse, with multiple advanced systems specializing in thermal balance and high-wear resistance.

Some of the must-considered products include the EMS‐AUTOMO SYSTEM for large automotive exterior and interior parts, the S-RHEO SYSTEM for quicker color change, and the PRM-ECON SYSTEM, known for its high performance. Want to know more about the products, their specific details, features, and pricing? Check out the CHRS website.  

Wrapping It Up!

Hot runner and cold runner systems have multiple applications in the injection molding industry. However, sometimes, it becomes difficult for consumers to choose one out of them. To put it short, it’s up to you which factor is more important for you. If you are into making complex parts, blindly choose hot runner systems. If you want to skip maintenance costs and enjoy the lower initial investment, choose cold runner systems. So, it's your preferences and needs that can help you better decide between the two systems.

Hope this info proved helpful. Stay tuned for more! Be sure to check out CHRS if you plan on getting premium hot runner systems.