Part of the leakage situation, not because of poor system design, but because the design parameters did not operate. Leaks usually occur between the hot nozzle and the splitter board. According to the design specification of the general Hot runner, there is a steel edge in the nozzle to ensure that the height of the nozzle assembly is less than the actual groove depth on the hot runner plate. The purpose of the design of this poor size (usually called the cold gap) is to avoid thermal expansion resulting in damage to parts when the system is operating at a temperature.
1. The hot nozzle is fixed on the shunt plate and the high temperature bolt fixed on the shunt plate can prevent the leakage under the cooling condition. This system still needs cold clearance, because the steel edge at room temperature needs a certain expansion space. Although this method can proactively prevent the leakage of the hot nozzle to the shunt plate, it cannot prevent the thermal expansion of the components under overheating conditions.
2. The hot nozzle which is fixed on the shunt board by Bolts is moving with the shunt plate. This design has the minimum length requirement for the hot nozzle, and also limits the spacing of the die cavity. It is an economical and effective way to prevent leakage between hot nozzle and shunt plate, and it is suitable for the system with less die cavity number.
3. The edge of the hot nozzle is designed with elasticity rather than steel, and the elastic edge provides preload under cooling conditions and prevents system damage. If the accident heats up excessively, it can also absorb the thermal expansion, causes the operation scope to extend to the ±110℃.