Mold manufacturers are worried that a problem is the hot runner leakage problem.
In the hot runner system, the melt leaks into the manifold slot. In most cases, the leakage of the hot runner system is not due to poor design, but because it is not in accordance with the design parameters to operate. Typically, the leakage occurs at the seal between the hot mouth and the manifold. According to the general design specifications of the hot runner, there is a steel edge at the hot mouth that ensures that the height of the hot mouth assembly is less than the actual groove depth on the hot runner plate. The reason is to design this size difference (often called a cold gap), the purpose is to avoid the system at the operating temperature will not damage due to thermal expansion of parts. For example, for a 60 mm thick manifold and a 40 mm hot mouth assembly (total height of 100 mm), the temperature typically rises by 0.26 mm after the temperature has risen to an operating temperature of 230 ° C. If there is no cold gap, thermal expansion tends to cause damage to the edge of the hot mouth. Therefore, there is no effective seal in the cooling conditions is caused by hot runner leakage of the main reasons.
In general, in order to ensure the sealing of the system (hot mouth and manifold), the system must be heated to the operating temperature so that the resulting force is sufficient to counteract the injection pressure, thereby preventing the injection pressure from opening the two parts. In general, inexperienced operators often do not wait for the system to reach operating temperatures, and worse, they may even forget to turn on the heating system. In this way, the hot runner with a cold gap does not prevent the leakage of material before it reaches its operating temperature.
In addition, in the case of excessive heating may also occur leakage material phenomenon.
Due to the poor adaptability of the hot mouth at the edge of the strip, when the system is overheated, once again reduced to the operating temperature, the resulting sealing pressure can not prevent leakage due to the deformation of the steel. In this case, in addition to leakage will cause damage to the system, but also because the pressure is too large and the nozzle caused irreparable damage, which need to replace the hot mouth. Due to the importance of the preheat of the hot mouth and the manifold, it is necessary to strictly follow the size and tolerances provided by the hot runner supplier in order to effectively prevent the system from leaking.
Therefore, for the mold manufacturers, should be based on the hot runner supplier drawings require careful inspection of all the hot mouth component height and groove size, if any problems, but also with the hot runner suppliers in time to communicate.