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What is a hot runner?


As a common component of the mold system, the hot runner system can effectively improve the quality of plastic products, improve production efficiency, and make higher returns on capital investment.

Insert molding technology, co-injection molding technology and multi-component injection molding technology are inseparable from the support of hot runners. A large number of components, such as automobile bumpers, can only be formed by hot runner molds due to flow path limitations, wall thickness ratios, and fusion seam problems. In injection molding, the role of the hot runner system is becoming more and more important.

Although the hot runner and the injection mold are one unit, its function and function are completely different from the mold itself. For the individual units of the system, the installation, connection and operation have special high-precision position requirements. For these reasons, the assembly of the hot runner system becomes a bottleneck in the mold installation. Therefore, avoiding errors in the hot runner system installation process and simplifying system connections and saving assembly time becomes an important issue.

Conventional hot runner design

The hot runner system is derived from the hot runner system. Usually, the nozzles are not always mounted on the manifold or they can be attached to the nozzle flange, but such systems require a fixed plate to maintain the integrity of the system. For most plastics processing, there is a temperature difference between the hot runner and the mold due to the temperature of the mold approaching 200 °C. If the system is attached to the mold plate, it will raise the temperature and increase the loss of heat, and a flow dead angle may also occur between the splitter plate and the nozzle.

When the hot runner requires maintenance, the hot runner must be completely removed from the mold. Since the nozzle is not connected to the manifold, the electrical and hydraulic lines must be completely disassembled and connected after the inspection is over.

Combined hot runner system

In a combined hot runner system, the nozzle and manifold form a simple unit. The melt flows directly from the manifold into the nozzle so that no deviations and flow dead angles occur. The threaded nozzle is embedded in the manifold, eliminating leakage between the nozzle and the manifold. Traditional bushing system designs create thermal expansion, and such combined systems are particularly effective at eliminating such leaks.

The combined hot runner system is located at the center of the mold and has little coupling to the mold. The material of manufacture does not require high thermal conductivity, nor does it require clamping and pre-tensioning of the mold. This minimal connection provides a high precision and stable temperature profile, so energy consumption is much lower than with conventional hot runner systems.

The combined hot runner system is capable of directly pre-assembling hydraulic lines that are independent of the mold. Valve ports that are directly driven by hydraulic equipment can also be mounted directly on the system, thus omitting the control valves on conventional machines, making injection molding more flexible. In addition, electrical and hydraulic lines can also be configured according to customer requirements. Since the system is subjected to electrical, temperature, hydraulic or pneumatic testing prior to delivery, the customer will be provided with a pre-installed system description that can be easily installed in the mold and put into production immediately.

When the mold or system requires routine maintenance, the combined hot runner system can also be removed from the mold in a simple step so that it can be repaired and tested independently of the mold.

Typically, combined hot runner systems reduce maintenance costs. The complete hot runner system is based on a combined pre-design and installation where the heater or thermocouple wires are removed during assembly. The wires connecting the heater to the distribution box are placed in a specially designed conduit which is advantageous for the removal of the mold or hot runner system. At the same time, the integrated hot runner system enables day-to-day maintenance without disassembly, saving time and reducing the chance of assembly errors.

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