Why is the temperature of plastic bottle cap compression molding lower than that of injection molding?


Plastic bottle caps are the most common sealing method for bottles, cans and barrels, especially in the fields of beverages, medicine and chemical industry. For bottle caps, we should pay more attention to the "one more bottle" inside the bottle cap.

Generally speaking, the production process of plastic bottle caps is roughly divided into two types: the production process of compression molded caps and the production process of injection caps

Why the molding temperature of compression molding process is lower than that of injection molding.

Let us first look at the molding temperature on the injection molding process. As you can see, the melting temperature of the plastic is set to about 220 ° C, and the temperature of the mold cooling water is 10 ° C.

The temperature setting of the compression molding process is much simpler than the temperature setting of the injection molding process, there is no hot runner temperature setting, and the number of barrel temperature sections is also small. The plastic melting temperature is set to about 180 ℃, and the mold cooling water temperature is 15 ℃.

In general, the temperature setting of the compression molding process has the following characteristics: 1. The temperature of the barrel is about 40 ° C lower than that of the injection molding process, and the advantages of the heating energy consumption of the compression molding process are immediately highlighted. It is about 5 ℃ high, so the chiller of the compression molding process does not need to consume too much energy to cool, and it can even be cooled with normal temperature water, which also saves considerable energy. For two different molding processes, we are now in There are already very clear comparative data on heating temperature and cooling temperature. Now, let's analyze it again. Why does the injection molding process require such a high melting temperature and such a low cooling temperature? Why doesn't the compression molding process require too high a melting temperature or too low a cooling temperature?

Injection molding is a very complicated molding process. The injection molding machine needs to advance the screw at high speed to eject the molten plastic out of the nozzle of the barrel, and then into the hot runner, through a very small pin-point hot nozzle, and finally enter the mold cavity, During this process, the melted plastic will encounter a lot of resistance, which requires very high pressure to be injected smoothly, so the plastic must maintain a very good flow state to achieve this purpose. In order to achieve such a good flow state of plastic, the moment the plastic particles enter the screw from the lower hopper, the screw must consume a lot of energy to rotate at high speed, and the plastic particles friction between the screw and the inner wall of the barrel under an environment of up to 220 ℃ And the shearing can reach the full melting state and the state suitable for injection molding.

If the melting temperature of the injection molding process is set to be relatively low and the melting state of the plastic is relatively poor, even if the maximum pressure of the injection molding machine screw is used, the plastic cannot be smoothly passed into the mold cavity, which will cause the problem of lack of glue on the bottle cap.

After careful analysis and comparison above, it is believed that many bottle cap manufacturers will tend to choose the compression molding process when adding new production lines

Compression molding machinery is known as the most cost-effective banknote printing machine in the bottle cap industry. The energy consumption saved in long-term production will greatly increase the profitability of the bottle cap factory. Ouming cap compression molding machine cut 30% blowing costs, reduce 46% power consumption, get high reputation in bottle cap machinery.

Why is the temperature of plastic bottle cap compression molding lower than that of injection molding?
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