The film produced is suitable for all kinds of high-grade film packaging. This kind of film can be widely used in light and heavy packaging due to its good barrier property, fresh keeping, moisture prevention, frost prevention, oxygen isolation and oil resistance. Such as all kinds of fresh fruits, meat, pickles, fresh milk, liquid drinks, medical supplies, etc. The cooling methods of plastic film blowing machine can be divided into two types: external cooling and internal cooling.
 
1. The external cooling method is the earliest application method. Under the action of the cooling ring, cooling air is released from a circular ring along the extrusion direction and the outer surface of the membrane bubble to generate uniform cooling air around the ring. Inside the cooling ring, the air at the upper port is discharged at a faster average speed than at the lower port. The shape of the membrane bubble is ensured to be consistent with the air cooling ring, so that the average flow rate of air is increased and thus the heat transfer is improved.
 
2. Internal cooling directly achieves the cooling purpose through film bubble heat dissipation. Because the flow rate of air in the membrane bubble is relatively low and irregular, external cooling is dominant. In the blow molding process of the film blowing machine, in order to ensure the quality of the film products, the stability of the film bubble before the film is formed must be considered, so as to effectively control the qualified rate of the products. The output of blow-molded film by the film blowing machine is not only restricted by film bubbles, but also takes into account the cooling system of the film blowing machine. A perfect cooling system requires reasonable configuration and stability of the film blowing machine.