Blow molding machine is a plastic processing method that involves inflating softened thermoplastic parisons within a closed mold surface. The inflated parison solidifies to form a hollow plastic product. What is the detailed principle and working process of blow molding machine?
Blow molding, also known as hollow blow molding, is a rapidly developing plastic processing method. A tubular plastic parison made of thermoplastic resin is molded by extrusion or injection. While still hot or softened by heat, it is placed in an open mold and immediately inflated with compressed air inside the parison, causing the plastic to expand and tightly adhere to the inner walls of the mold. After cooling and demolding, various hollow products are obtained. The manufacturing process of blow-molded films is similar in principle to that of hollow products, but molds are not used. Here, we recommend you our hdpe blow molding machine.
From the perspective of plastic processing technology classification, the forming process of blow-molded films is usually considered part of the extrusion production line. The blow molding process was first used to produce low-density polyethylene bottles 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 produced by blow molding can reach thousands of liters, and some productions are computer-controlled. Blow molding machines are suitable for blowing plastics such as polyethylene, PVC, polypropylene, polyester, and the resulting hollow containers are extensively used as industrial packaging containers.
Simply put, the working principle of a blow molding machine produced by the blow molding machine factory is similar to blowing bubbles. After the plastic and the hopper enter the screw barrel of the extruder, they are pushed toward the head by the rotation of the screw thread. Due to the resistance of the filter, splitter plate, and head die at the head of the machine, as well as the gradually decreasing capacity of the screw thread, the advancing material encounters great resistance, while also being heated by the heat transmitted from the barrel. On the other hand, when the plastic is subjected to forces such as compression, shear, stirring, etc. during movement, friction between the plastic and the barrel, between the screw threads, and between plastic molecules will produce a large amount of heat. Since the temperature of the plastic inside the barrel keeps rising, its physical state gradually changes from the glassy state to the high elastic state, and finally becomes the molten state, further completing plasticization. As the screw continues to rotate, the molten plastic is extruded from the head die in a pressure-balanced and constant amount, forming a plastic product with a certain shape. After cooling and shaping, the extrusion molding work is completed.
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