How the blow molding machine works?

The basic working principle of the blow molding machine is: inflate the softened thermoplastic parison to make it close to the cooling surface of the closed mold, and the inflated parison solidifies to form a hollow plastic product. The detailed principle and workflow will be detailed in this article. 

1. What is a blow molding machine

Blow molding, also known as hollow blow molding, is a rapidly developing plastic processing method. The tubular plastic parison obtained by extrusion or injection molding of thermoplastic resin is placed in a split mold while it is hot (or heated to a softened state), and compressed air is introduced into the parison immediately after closing the mold to blow the plastic parison. It expands and sticks closely to the inner wall of the mold, and after cooling and demoulding, various hollow products are obtained. The manufacturing process of blown film is very similar in principle to blow molding of hollow products, but it does not use a mold. From the perspective of plastic processing technology classification, the molding process of blown film is usually included in extrusion. The blow molding process began to be used to produce low density polyethylene vials during World War II. In the late 1950s, with the birth of high-density polyethylene and the development of blow molding machines, blow molding technology was widely used. The volume of hollow containers can reach thousands of liters, and some production has adopted computer control. Plastics suitable for blow molding include polyethylene, polyvinyl chloride, polypropylene, polyester, etc. The obtained hollow containers are widely used as industrial packaging containers

2. the working principle of the blow molding machine

Simply put, the working principle of the blow molding machine is similar to blowing bubbles. After the plastic and the hopper enter the extruder barrel, the

The rotation is forced to the direction of the machine head by the thread. Due to the resistance of the filter screen, the dividing plate and the die of the machine head at the head, and the capacity between the screw threads is gradually reduced, the advancing material is subject to great resistance, and at the same time, it is heated by the heat introduced by the barrel; on the other hand , When the plastic is under the action of compression, shearing, stirring and other forces during the movement, the friction with the barrel, the screw and the friction between the plastic molecules will generate a lot of heat. As the temperature of the plastic in the barrel continues to rise, its physical state gradually changes from a glassy state to a highly elastic state, and finally becomes a viscous state, and is further completely plasticized. Because the screw is constantly rotating, the plasticized plastic is extruded from the die of the die at the same pressure and in the same amount, which is called a plastic product with a certain shape. After cooling and setting, the extrusion molding work is completed.