Blow moulding (also known as blow moulding or blow forming) is a manufacturing process by which hollow plastic parts are formed. In general, there are three main types of blow moulding:
Extrusion blow moulding,
Injection blow moulding, and
Stretch blow moulding.
The blow moulding 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.
History of blowing
Enoch Ferngren and William Kopitke were the first verified people who used the blow moulding process. The process principle comes from the idea of glassblowing. Ferngren and Kopitke produced a blow moulding machine and sold it to Hartford Empire Company in 1938. This was the beginning of the commercial blow moulding process. During the 1940s the variety and number of products was still very limited and therefore blow moulding did not take off until later. Once the variety and production rates went up the number of products created followed soon afterwards. In theUnited States soft drink industry, the number of plastic containers went from zero in 1977 to ten billion pieces in 1999. Today, even a greater number of products are blown and it is expected to keep increasing.