Fresh-keeping box moulds generally use high-permeability PP material, and the appearance of the product requires high smoothness and good permeability. Then, what effect does the mould hot runner system, heating system and cooling system have on the surface of the fresh-keeping box mould?
The hot runner system is very important for the fresh-keeping box mould. The quality of the hot runner is the decisive factor whether or not a product without weld marks can be injected. The characteristics of the hot runner system of the high-gloss mould: the hot nozzle of the mould must be equipped with a sealing needle, and each hot nozzle must have an independent air passage. In this way, it is possible to individually control the glue feeding time and amount of each hot nozzle through the solenoid valve and the time relay, making necessary preparations for the injection moulding machine.
When the plastic material is injected into the mould cavity of the fresh-keeping box, within a reasonable temperature range, the higher the surface temperature of the mould cavity, the better the surface quality of the product, and the smaller the internal stress of the product. Therefore, in order to obtain a good product surface quality, increasing the cavity surface temperature is a good way. However, increasing the mould temperature will reduce the injection efficiency, which requires comprehensive consideration. Generally, the mould of the fresh-keeping box must be heated by a mould temperature machine during injection moulding, so that the plastic can be kept under pressure and temperature at a high temperature in the mould, so as to eliminate defects such as flow marks and weld marks.
Good waterway arrangement can not only greatly improve injection efficiency, but also play an important role in improving product quality. The water channel of the fresh-keeping box mould must not only be uniform, but also must be sufficient, so that the required temperature can be easily reached. At the same time, the use of an extended water pipe to directly transport the mould core without using a sealing ring can prevent the mould from working under high temperature for a long time, causing the sealing ring to age, and can also reduce the maintenance cost of many moulds. It is worth mentioning that the water pipe of the fresh-keeping box mould must be made of high-temperature resistant oil pipe to prevent the water pipe from bursting under high temperature and high pressure.
