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| What is the hot runner system's disadvantage? |
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| Comparing with the cold runner and three-plate molding, the operation of hot runner system needs the support of more technicians and the experienced senior maintainers. The molding maintenance needs long time and the parts can be easily damaged. As the heaters can be easily damaged, so the certain electrical maintenance is also required, as the diameter of the hot runner nozzle is very small which can be easily blocked. As to the parts and materials which can be formed under major pressure (such as the thick-wall cover of the hand-set electrical products), the thin nozzle usually will be broken earlier. The pin of the nozzle is required in good thermal conductivity and also can be with good wear-resistance (as it can bear the brush of the periodically high-speed flowing melting materials). The hot runner system has higher requirement on the process precision of the gate. The mismatch of the design and the using parameter can make the internal leakage of plastic. The cost will be caused as the hot runner system will produce the radiation and loosing thermal power. The nozzle without pin valve being long-term open status will be casting, and then there will be solidified plastics on the cavities which need to be removed. The size of the runner needs to be counted carefully, as too small of the size, the stress will be loosed; as too large of the size, the temperature will be uneven due to the bad thermal conduction of the plastic materials. The delivery time of the hot runner system is long normally. As the manifold and the front & back plate need to be made according to the special craft request for each customer, and the design and producing is made against the design of the mold. |
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