The hot runner mold, also known as the hot runner system, is mainly composed of a hot sprue bush, a hot runner plate, and a temperature-controlled electric box. Our common hot runner systems are available in single-point hot gates and multi-point hot gates. The single-point hot gate uses a single hot sprue sleeve to directly inject the molten plastic into the cavity. It is suitable for a single-cavity single-gate plastic mold. The multi-point hot gate branches the molten material to each through a hot runner plate. The thermowell is then reintroduced into the cavity, which is suitable for single-cavity multi-point feed or multi-cavity molds.
Advantages of hot runner systems
(1) Water-free material, no post-processing is required, which makes the whole molding process completely automatic, saves working time and improves work efficiency.
(2) The pressure loss is small. The hot runner temperature is equal to the temperature of the injection nozzle of the injection molding machine, which avoids the surface condensation of the raw material in the runner and the injection pressure loss is small.
(3) Repeated use of the nozzle material will degrade the performance of the plastic, and the use of the hot runner system without the nozzle material can reduce the loss of raw materials and thus reduce the product cost. The temperature and pressure in the cavity are uniform, the stress of the plastic part is small, and the density is uniform. Under a small injection pressure, a shorter molding time, the injection molding is better than the general injection molding system. For transparent parts, thin parts, large plastic parts or high-demand plastic parts, it can show its advantages, and it can produce larger products with smaller models.
(4) The hot nozzle adopts standardized and serial design, and is equipped with various nozzle heads for easy interchangeability. The unique design and processing of the electric heating ring can achieve uniform heating temperature and long service life. The hot runner system is equipped with a hot runner plate, a thermostat, etc. The design is exquisite, diverse, easy to use, and the quality is stable and reliable.
Inadequacies in the application of hot runner systems
(1) The overall mold closing height is increased, and the overall height of the mold is increased due to the addition of hot runner plates.
(2) Thermal radiation is difficult to control. The biggest problem with hot runners is the heat loss of the runner, which is a major issue that needs to be solved.
(3) There is thermal expansion, and thermal expansion and contraction are issues that we should consider when designing.