In general, there are three main types of blow molding machines: extrusion blow molding machine, injection molding machine, and stretch blow molding machine.

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 basic process has two fundamental phases. First, a preform (or parison) of hot plastic resin in a somewhat tubular shape is created. Second, a pressurized gas, usually air, is used to expand the hot preform and press it against a mold cavity. The pressure is held until the plastic cools. This action identifies another common feature of blow molded articles. Part dimensional detail is better controlled on the outside than on the inside, where material wall thickness can alter the internal shape. Once the plastic has cooled and hardened the mold opens up and the part is ejected.

A blow molding renaissance is occurring in which engineers and designers are discovering and promoting blow molding for a wide variety of industrial or technical application. Toy wheels, automobile seat back, ductwork, surf boards, bellows, fuel tanks, flower pots, automobile bumpers, double- walled tool cases, and cabinet panels are just a few examples of the many creative design being developed.