Enoch Ferngren and William Kopitke were the first to verify the blow molding process. The principle of this process is derived from glass blowing. In 1938, Ferngren and Kopitke built a blow moulding machine and sold it to the Hartford Reich. This was the beginning of commercial blow molding. In the 40s of the 19th century, the variety and quantity of plastic products were very limited, so the blow molding process did not develop rapidly until very late. With the increase of product types and the improvement of productivity, more and more plastic products were soon produced by the blow molding process. In the U.S. soft drink industry, the number of plastic containers grew from zero in 1977 to 10 billion in 1999.
The blow molding process began to be used to produce low-density polyethylene vials during World War II. In the late 50s, with the birth of high-density polyethylene and the development of blow molding machines, blow molding technology was widely used. Hollow containers can reach thousands of litres in volume and some have been computer-controlled. Plastics suitable for blow molding are polyethylene, polyvinyl chloride, polypropylene, polyester, etc., and the resulting hollow containers are widely used as industrial packaging containers.
According to the billet production method, blow molding can be divided into extrusion blow molding and injection blow molding, and the newly developed multi-layer blow molding and stretch blow molding.
The extrusion process is to squeeze the plasticized plastic into the extrusion die head through the screw, and then cooperate with the following mold and compressed gas to achieve the molding of the product.
The extrusion blow molding process consists of 5 steps:
1. Make the plasticized raw materials into plastic embryos;
2. Intercept part of the embryo and cut off the embryo by closing the mold;
3. Fill the mold cavity with gas to form the preform and cool it;
4. Open the mold and take out the formed container;
5. Trim the flashing to get the finished product.
