Nowadays, the market is increasingly inclined to use hot runner systems, and like many technologies, the emergence of hot runner systems is to do things better and faster with less cost. The cold runner system causes waste every time the mold is opened, and when injection molding components, the multi cavity cold runner system causes a large amount of raw material waste, which seriously damages the profit space of the mold maker.

The cost savings of raw materials are the main driving force for switching to hot runner systems; Another factor is the shortened delivery time. Mold makers and mold manufacturers are increasingly demanding precision in their processes and processing techniques, which has led to a growing interest in hot runners.

Although the hot runner system has many significant advantages, in order to ensure the appropriate and most efficient injection molding process, it is also necessary to consider specific application situations, such as part size, aesthetic requirements, yield, raw materials, and additives.

When simplifying the injection molding process and reducing part waste, it is important to eliminate the need for a large accessory cold runner for injection molding. The key is to ensure that the melt remains in a molten state throughout the entire flow channel system, so that it does not solidify before reaching the cavity wall for cooling.

Internally heated hot runner

The internal heating hot runner system was the first batch of hot runner systems to be put into the market, and their emergence went through multiple steps. The first solution developed to solve various problems with the cold runner is to heat the nozzle, thereby creating maximum efficiency for the production of components. The second method developed is a tubular hot runner system. In this technology, the main runner is heated, and the molten resin flows from there to the unheated vertical runner, which then flows into the mold cavity through the nozzle. Another group of mold makers, who appeared approximately the same period as the tubular hot runner system, began placing heated probes into each vertical runner, leading to unheated insulated runners. Due to the cooling of the insulated runner at the nozzle, it is difficult to maintain "circulating" operation. The key is to ensure that the resin remains in a molten state when passing through the nozzle. These three technologies were later combined to form an "internally heated" hot runner system.

The internal heating hot runner system may be more complex than the cold runner system, but it makes the processing of difficult to treat resins more flexible and reduces resin waste. Due to the circular geometry of the flow channel, the internally heated hot runner can effectively handle resins that are not overly sensitive to shear, as well as amorphous materials that are also suitable for this technology (except for materials that are sensitive to residence time, such as polycarbonate)

Until today, due to the high cost of externally heated hot runner systems and the need for some experience in their use, some mold makers still insist on using internally heated hot runner systems, even cold runners.

Externally heated hot runner

At the beginning of the external heating hot runner, it is a steel brick with an internal channel provided for the molten resin. The heater fixed around the outside of the steel brick heats the runner plate from the outside to evenly heat the inside. Next, the melt is dispersed throughout the heated runner plate, enters the heated nozzle, and is sent to the final nozzle, where it flows into various cavities.

The advantages of a hot runner system are obvious. With a reasonable design, this system can achieve maximum injection molding capacity while effectively eliminating material waste during each injection cycle, achieving a "win-win" situation. As a hot runner company specializing in the production of hot runner systems for over a decade, Haochen Hot Runner strongly recommends the use of hot runner systems to injection molding product manufacturers, as it not only saves a lot of raw materials, but also brings various other conveniences to the mold maker's processing process.

It is worth noting that it is difficult to create a completely smooth heated trace from the inlet of a hot runner system to each hot nozzle. Some hot runner systems may achieve this effect, but there are always times when the resin needs to cool down just at the nozzle to prevent wire drawing or salivation. Moreover, the flow rate and injection rate have a significant impact on resin processing and color change. The design of a hot runner system is very suitable for one resin, but it is not uncommon for it to be unsuitable for another resin. A slight shaping of the heated traces can usually correct these issues. Regardless of the type of hot runner used by the designer, the resin used and the application of injection molded parts should be considered.