Today, insert molding technology, co-injection molding technology, and multi-component injection molding technology all rely on the support of hot runner systems. A large number of components such as automotive bumpers can only be processed and molded using hot runner molds due to restrictions on flow paths, wall thickness ratios, and weld line issues. In injection molding, the role played by hot runner systems is becoming increasingly important.
                      
Although the hot runner and the injection mold form an integrated whole, its functions and roles are completely different from those of the mold itself. As independent units of the system composition, their installation, connection, and operation have special high-precision positional requirements. For these reasons, the assembly of the hot runner system has become a bottleneck in mold installation. Therefore, avoiding errors during the installation of the hot runner system, simplifying system connections, and saving assembly time have become an important research topic. 
Conventional Hot Runner Design 
The hot sprue system is derived from the hot runner system. Usually, the nozzle is not always mounted on the manifold, but can also be loosely connected to the nozzle flange, but such systems require a fixing plate to maintain the integrity of the system. For most plastic processing processes, since the mold temperature is close to 200°C, there is a temperature difference between the hot runner and the mold. If the system is connected to the mold plate, it will increase the temperature and heat loss, and flow dead zones may also occur between the manifold and the nozzle.
                      
When the hot runner requires maintenance, the hot sprue must be completely removed from the mold. Since the nozzle is not connected to the manifold, the electrical and hydraulic lines must be completely disconnected and reconnected after the maintenance is completed. 
Modular Hot Runner System 
In the modular hot runner system, the nozzle and manifold form a simple unit. The melt flows directly from the manifold into the nozzle, thus no deviation or flow dead zones are generated. The threaded nozzle is embedded into the manifold, eliminating leakage between the nozzle and the manifold. Traditional bushing system designs produce thermal expansion, and this modular system is particularly effective in eliminating such leakage. 
The modular hot runner system is located at the center of the mold with few connections to the mold. Its manufacturing materials do not require high thermal conductivity, nor do they require clamping or pre-tensioning of the mold plates. This minimal connection provides high precision and a stable temperature profile, resulting in much lower energy consumption compared to traditional hot runner systems.
 
The modular hot runner system can be directly pre-assembled with hydraulic lines independent of the mold. Valve gates driven directly by hydraulic equipment can also be installed directly on the system, which eliminates the control valves on traditional machines and makes injection molding more flexible. In addition, electrical and hydraulic lines can be configured according to customer requirements. Since the system undergoes electrical, temperature, hydraulic or pneumatic testing before delivery, customers receive instructions for the pre-installed system, making it easy to install in the mold and put into production immediately. 
When the mold or system requires regular maintenance, the modular hot runner system can be removed from the mold with the same simple steps, allowing repair and testing to be performed independently of the mold. 
Generally, the modular hot runner system reduces maintenance costs. The complete hot runner system is based on modular pre-configured design and installation, with the wires of heaters or thermocouples removed during assembly. The wires connecting the heaters and the distribution box are placed in a specially designed conduit, which is beneficial for the disassembly of the mold or hot runner system. At the same time, the integrated hot runner system can perform daily maintenance without disassembly, saving time and reducing the probability of assembly errors.