Hot runner in injection molding helps accurately manufacture plastic components that cater to numerous industries. If you want to know about the hot runner system in injection molding, you are at the right place. The guide below features a detailed insight into many things you might need to know about hot runners, so let’s read below.
What is Hot Runner in Injection Molding?
A hot runner in injection molding is a system with a conveying unit that helps to let molten plastic flow in the mold or cavity to manufacture the required plastic component.
The hot runner system is a system that is present in injection molding machines comprising heated components.
This system has a temperature controller that allows heating of the hot runner, and the plastic is even heated within the machine to enable injecting in the mold.
The hot runner is responsible for bringing the plastic in molten form from the barrel of the machine and dropping it into the cavities for the plastic to take its shape. The size of the hot runner in injection molding depends on factors like the kind of plastic used and the filling rate
The molten plastic travels through the hot runner system and then splits into different nozzles, allowing molten material to be injected into the mold.
What are the Main Elements of a Hot Runner?
The hot runner system used in injection molding has different elements that play an essential role in the system’s functioning process. These elements include the following:
- Nozzles help in injecting the plastic in molten form into the molds.
- The heater maintains the temperature of the plastic throughout the process.
- Manifolds carry out the task of distributing plastic in the nozzles.
- The temperature controller helps in regulating the temperature of the system.
- Insulation keeps the loss of heat under control and also stabilizes the temperature.
- Valves Control the flow of plastic in the molds.
- Flow channels let the plastic flow into the system.
How Does a Hot Runner Injection Molding System Work?
The working mechanism of hot runner injection molding comprises multiple components and stages, and these are discussed below:
- The system comprises a locating ring, which creates an alignment between the injection mold and the surface base of the molding machine. It helps to ensure that the mold aligns with the machine properly so that when the molten plastic flows, it is collected ideally in the cavity.
- Once the alignment is achieved, the molten plastic is injected into the mold, and the molten plastic is first heated to turn into a liquid form, making it easier for the plastic to flow uniformly. The hot runner system collects the plastic from the barrels and allows it to pass through the heated components it has within itself.
- The molten plastic then flows to the nozzles and divides into different segments the nozzle of the machine has; the number of segments will depend on the nature and shape of the component.
- The nozzle then pours the molten material into the cavities present on the base of the molding machine.
What is the Function of Hot Runner in Injection Molding?
The hot runner in injection molding has various functions, and each function adds quality and uniformity to the plastic component produced. Some of the parts of the hot runner in injection molding are discussed below:
Distribution of Plastic
The primary function performed by the hot runner system is the distribution of the molten plastic, This distribution takes place from the nozzle of the injection molding machine to the different cavities. It eliminates the requirement for sprues and runners to be subjected to recycling or discarding.
Reduction in Wastage
Hot runner systems also increase material efficiency because they reduce the wastage of material and help in cost saving in the long run.
Short and Fast Cycle Times:
The cycle times offered by hot runner systems are faster when compared to cold runner systems.
Maintaining Constant Temperature
Hot runner systems are responsible for maintaining a consistent temperature; hence, proper filling occurs, reducing defects like sink marks, flow lines, and warping.
Controlling Flow Through Valves
These systems are even suitable when gating controls are in place, like the use of thermal and valve gates allowing the control of the flow of plastic in molten form when subjected to the mold cavity; it helps to ensure that the quality of the component is improved and the scrap is reduced.
Catering to Complex Geometries
Hot runner systems can accommodate multiple mold designs with complex geometries, catering to a wide range of applications that require injection molded components.
Transitioning between Materials
Hot runner systems even allow the creation of a transition between different materials and colors in a single plastic component, which is quite efficient and helps save time.
Uniform Filling of Plastic
The hot runner systems are even suitable for manufacturing parts with complex geometries and tight tolerance. This method offers precise control over the plastic flow and ensures a consistent filling in the molds.
How Many Types of Hot Runners Are Used in Injection Molding?
Three different kinds of hot runner systems are used in the injection molding process, and these may include the following:
Hot Tip Hot Runner Systems
The hot tip hot runner systems are widely used because of the different nozzles and precise pouring they offer. The best part is that this kind of hot runner system allows for precisely controlling and adjusting the molding process’s temperature.
This system is popular with many crystalline and non-crystalline materials and offers the production of small and medium-sized plastic parts. Micro parts can also be produced.
Sprue Gating Hot Runner Systems
In the sprue-gating hot runner system, the material enters the mold through a smooth pipe with an open end. This system is ideal for producing parts that are large as well as medium.
The best thing about this kind of system is that it has a low shear rate and less stress reduction, which offers great strength on the part of the plastic component. This kind of system is used widely for components that are either internal or do not need much aesthetic beauty.
Valve Gating Hot Runner Systems
The valve gating hot runner is a widely used hot runner system with a valve pin controller. It offers an automated system that opens and closes the gate simultaneously.
It is one of the most accurate and precise systems, offering high efficiency and a better quality output.
Advantages and Disadvantages of Hot Runner System
Advantages of Hot Runner System
Some of the advantages of the hot runner system are as follows:
- Design flexibility is one of the main factors that makes the hot runner system the best choice. It allows manufacturing the parts with complex and intricate designs and shapes and offers an aesthetic appearance other than uniformity.
- The efficiency of this process is also commendable. It requires lower pressure of injection, and also, there is a reduction in mold deflection. Hence, it helps in producing better quality components efficiently.
- The hot runner system is equipped with flow advantages; the channels comprising the melting process are present in different manifolds, and they have better insulation than the cold runner systems. They have built-in control for pressure and temperature and hence offer precise flow, which is well controlled.
- The parts manufactured through hot runner systems offer dimensional consistency; these runners do not get tangled and hence help in automated processes.
- The quality of the component manufactured is optimal, and it offers better uniformity by balancing the melt flow at a consistent temperature. Therefore, an accurate quality-oriented part is achieved.
- The initial investment in the hot runner system for injection molding is high, but in the long run, it is extremely cost-effective because of the reduced cycle time and waste.
- The hot runner system helps with time-saving and reduces the cycle time, which makes the entire manufacturing process quite efficient.
Disadvantages of the Hot Runner System
Along with advantages, there are some disadvantages of the hot runner system that cannot be ignored and need to keep an eye on; some of these are discussed below:
- The hot runner system needs to be taken care of, and it has technical and complex maintenance in case precaution is not taken, and the part of the hot runner may get damaged.
- The hot runner systems need a high level of machinery for injection molding to manufacture the components correctly. If supplied with the best machinery, there could be many things in the production process.
- Hot runner comprises costly components; hence, you may need a higher production rate to cover the cost of the hot runner system.
- Some of the hot runner systems even exhibit thermal expansion and contraction; hence, the heat produced during the process may sometimes be difficult to control.
- The hot runner system may also be used for heat-sensitive plastics, and they need extra care and expertise; if it is not exercised, the plastic may change its color or become a degraded version, leading to defects in the final product.
Conclusion
The hot runner systems are ideal for manufacturing different plastic parts through injection molding, which cater to different industrial applications. However, learning important things about these systems and familiarizing oneself is essential to better deal with them.
The details shared above helped you know about these systems and their pros and cons so that you can make the best use of them.
