Hot runner technology in injection molding has become a key advancement in the plastics industry, driven by the continuous improvement of plastic raw materials and their increasing application across various sectors. As a result, hot runner molds have gained significant popularity due to their numerous advantages over traditional cold runner molds. These benefits include shorter molding cycles, improved product quality, reduced scrap rates, material savings, elimination of post-processing steps, and expanded application possibilities for injection molding.
Despite these advantages, hot runner molds also come with certain challenges. Their complex structure increases manufacturing costs, makes maintenance more difficult, and presents issues such as local overheating and temperature imbalance within the system. Additionally, heat loss between the hot runner nozzles and the mold cavity can affect the consistency of the injection process, making it harder to maintain stable temperatures throughout the system.
Key technologies in hot runner systems revolve around maintaining a consistent molten state of the plastic throughout the entire flow path—from the injection machine nozzle to the mold cavity. This requires precise control of heating, insulation, and thermal management. The main components of the hot runner system include the hot runner plate, the manifold, and the nozzles, each playing a critical role in ensuring uniform heat distribution.
Heating methods for the hot runner plate typically fall into two categories: internal and external heating. External heating involves placing heating elements around the flow channels, which is less likely to cause overheating but has lower thermal efficiency. Internal heating, on the other hand, places the heating rods directly inside the flow path, offering higher efficiency but risking localized overheating and increased melt resistance.
The heating of nozzles is even more complex, often relying on empirical formulas rather than standardized calculations. Nozzles can be non-heated, externally heated, or internally heated. Non-heated nozzles rely on the heat from the hot runner plate, while externally and internally heated nozzles provide more direct control over temperature, though they come with trade-offs in terms of design and durability.
To ensure proper thermal separation between the high-temperature hot runner system and the cooler mold cavity, effective insulation is essential. Common insulation methods include using asbestos boards, air gaps, and low-conductivity materials. These measures help prevent heat transfer that could negatively impact the molding process.
Although hot runner technology is well-established in many developed countries, its adoption in China is still in the early stages. To promote wider use, efforts should focus on standardizing components, reducing maintenance complexity, and improving system reliability. With continued innovation and refinement, hot runner technology has the potential to become even more efficient and widely adopted in the future.
By addressing current limitations and enhancing system performance, hot runner technology will continue to evolve, supporting the growing demands of modern injection molding processes.
Heilongjiang Junhe Building Materials Technology Co., Ltd , https://www.junhejiancai.com