Enoch Ferngren and William Kopitke first validated the blow molding process. The principle of this process originated from glassblowing. In 1938, Ferngren and Kopitke built a blow molding machine and sold it to the Hartford Empire Company. This marked the beginning of commercial blow molding. In the 1840s, the variety and quantity of plastic products were very limited, so blow molding only saw rapid development much later. With the increase in product variety and productivity, blow-molded plastic products quickly became more and more common. In the US soft drink industry, the number of plastic containers grew from zero in 1977 to 10 billion in 1999.
During World War II, blow molding began to be used to produce low-density polyethylene bottles. In the late 1950s, with the advent of high-density polyethylene and the development of blow molding machines, blow molding technology became widely used. Hollow containers can reach volumes of several thousand liters, and some production processes are now computer-controlled. Plastics suitable for blow molding include polyethylene, polyvinyl chloride, polypropylene, and polyester. The resulting hollow containers are widely used as industrial packaging containers.
Based on the preform manufacturing method, blow molding can be divided into extrusion blow molding and injection blow molding. Newer methods include multilayer blow molding and stretch blow molding.
The extrusion process involves extruding plastic raw material through a screw into an extrusion blow die, which, combined with the mold and compressed gas, shapes the product.
The extrusion blow molding process consists of five steps:
1. Forming a plastic preform from the plasticized raw material;
2. Partially cutting and trimming the preform by closing the mold;
3. Injecting gas into the mold cavity to shape the preform and cooling it;
4. Opening the mold and removing the formed container;
5. Trimming the flash to obtain the finished product.
