Hot runner technology is an advanced technology applied to pouring runner system of plastic injection molds, and it is a hot direction in development of plastic injection molding technology.
So-called hot runner molding means that plastic sent from nozzle of injection machine to gate is always in a molten state. It does not need to be solidified and taken out as waste each time mold is opened. Molten material remaining in gating system can be injected into cavity during another injection.
Ideal injection molding system should produce parts with consistent density, free from all runners, flash, and gate sprues. Compared with cold runner, in order to achieve this, hot runner must maintain molten state of material in hot runner and will not be sent out with formed parts. Hot runner process is sometimes called a hot header system, or runnerless molding.
Basically, heat header can be thought of as an extension of barrel and injection molding machine nozzle. Role of hot runner system is to send material to each gate in mold.

 

As a common component of mold system, hot runner system can effectively improve quality of plastic products, improve production efficiency, and make capital investment get higher returns. Now, a new type of combined hot runner system debuts, what surprises will it bring us?
Today, insert molding technology, co-injection molding technology and multi-component injection molding technology are all inseparable from support of hot runners. A large number of parts, such as automobile bumpers, can only be processed with hot runner molds due to flow path restrictions, wall thickness ratios, and weld seam issues. In injection molding, role of hot runner system is becoming more and more important.
Although hot runner and injection mold are integrated, its role and function are completely different from mold itself. For independent unit of system, its installation, connection and operation have special high-precision position requirements. For these reasons, assembly of hot runner system has become a bottleneck in mold installation. Therefore, avoiding errors during installation of hot runner systems, simplifying system connections and saving assembly time have become an important issue.

Hot runner system is derived from hot runner system. Typically, nozzles do not always have to be mounted on manifold, but can also be virtually connected to nozzle flange, but such systems require a mounting plate to maintain integrity of system.
For most plastics processing, there is a temperature difference between hot runner and mold as mold temperature is close to 200℃. If system is attached to die plate, it will raise temperature and increase heat loss, there may also be a flow angle between manifold and nozzle.
When hot runner needs repair, hot runner must be completely removed from mold. Since nozzle is not connected to manifold, electrical and hydraulic lines must be completely disassembled and reconnected after overhaul.

In a combined hot runner system, nozzle and manifold form a simple unit. Melt flows directly into nozzle from manifold, so there is no deviation and no flow angle. Threaded nozzle is embedded into manifold, eliminating leakage between nozzle and manifold. Traditional bushing system designs generate thermal expansion, and this combined system is particularly effective in eliminating such leaks.
Combined hot runner system is located in the center of mold and has few connections with mold. Its manufacturing material does not require high thermal conductivity, nor does it require clamping and pretensioning mold sheet. This minimal connection provides a high accuracy and stable temperature profile, so energy consumption is much lower than traditional hot runner systems.
Combined hot runner system enables direct pre-assembly of hydraulic lines independent of mold. Valve ports that are directly driven by hydraulic equipment can also be installed directly on system, thus eliminating need for control valves on traditional machines and making injection molding more flexible. In addition, electrical and hydraulic circuits can also be configured according to customer requirements. Since system undergoes electrical, temperature, hydraulic or pneumatic testing before delivery, customers are given instructions to pre-install system, which can be easily installed in mold and put into production right away.
When mold or system requires routine maintenance, combined hot runner system can also be disassembled from mold in a simple step, allowing repair and inspection to be performed independently of mold.
In general, combined hot runner systems reduce maintenance costs. Complete hot runner system is based on a combined pre-assembled design and installation, where heater or thermocouple wires are removed during assembly. Wires connecting heater to distribution box are placed in a specially designed conduit, which facilitates disassembly of mold or hot runner system. At the same time, integrated hot runner system enables disassembly-free routine maintenance, saving time and reducing chance of assembly errors.