05
2022
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05
What problems of injection pressure must be considered in the hot runner system?
Customers may not be very careful about the application of the hot runner system. Today, Dent Hot Runner tells you that the injection pressure should be considered when selecting the hot runner system.
The injection pressure loss in the hot runner system cannot be ignored. Many hot runner mold customers have a misunderstanding: the plastic melt in the hot runner is always hot, so the injection pressure loss of the hot runner is much smaller than that of the cold runner.
In fact, in order to meet the needs of the hot runner structure design, the flow distance of the melt in the hot runner system will be greatly increased, so the injection pressure loss in the hot runner system cannot be underestimated. In practical applications, due to the excessive injection pressure loss in the hot runner system, there are many situations that cause injection molding difficulties. Therefore, for plastics with poor fluidity (such as PC, POM, etc.) and the flow distance of the melt in the hot runner system In the case of large size and heavy product weight, CAE software should be used for flow channel analysis and calculation.
After the production of the hot runner injection mold is completed, the shutdown steps similar to the injection machine are used, and the following operations must be performed:
1. Turn off the heater of the hot runner system.
Second, turn off the cooling system of the mold. For the heated hot runner system, the cooling system of the mold can only be turned off after the temperature drops to 80 °C.
Before the end of hot runner injection molding production, for high temperature plastics and heat sensitive plastics, refill cleaning must be carried out. For some plastics such as PC, it can stay in the hot runner system and the barrel of the injection machine. At a low temperature of about 160 °C, the injection can be interrupted for up to 12 hours, but it cannot be interrupted for a long time. Heat-sensitive plastics cannot interrupt injection. In the barrel of the injection machine and the flow channel of the hot runner, there is a strong adhesion between the cured or semi-cured plastic and the metal surface, and even the nitride layer is separated. The screw of the injection machine and the pin of the switch nozzle have a surface nitride layer. Therefore, do not interrupt the injection and perform a melt purge before shutdown.
E-mail: dghanmao656@126.com gongcheng @ himold.com
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Jiangxi Factory: Hexi Industrial Park, Xingan County, Jiangxi Province
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