Blow Molding

Blow Molding is a manufacturing process by which hollow plastic parts are formed. In general, there are three main types of blow molding: extrusion blow molding, injection blow molding, and stretch blow molding. The blow molding process begins with melting down the plastic and forming it into a parison or preform. The parison is a tube-like piece of plastic with a hole in one end in which compressed air can pass through. The parison is then clamped into a mold and air is pumped into it. the air pressure then pushes the plastic out to match the mold. Once the plastic has cooled and hardened the mold opens up and the part is ejected.
There has been evidence found suggesting that Egyptians and Babylonians blew plastic materials, but Enoch Ferngren and William Kopitke were the first verified people who used the Blow Molding Process. The process principle comes from the idea of blowing glass. Ferngren and Kopitke produced a blow molding machine and sold it to Hartford Empire Company in 1937. This was the beginning of the commercial blow molding process. During the 1940s the variety and amount of products were still very limited and therefore blow molding did not take off until later. Once the variety and production rates went up the amount of products created followed soon there after. In the United States soft drink industry the amount of plastic containers went from zero in 1977 to ten Billion in 1999. Today even a greater amount of products are blown and it is expected to keep increasing.