Blow Molding

The advantages of polyolefin blow holding resins are processability, light weight, good toughness, outstanding chemical resistance and relatively low cost compared to other plastics.

Major application areas for polyolefin blow molded products include:

Packaging for such products as milk and others foods, cleaning fluids, medicines, cosmetics and personal care products.
Automotive items, such as gas tanks, oil bottles and windshields fluids containers, air ducts and seat backs.
Consumer products, including toys, house wares and sporting goods.
Objects for materials handling, including 55 gallon drums and chemical carboys
Industrial products, such as business machine fluid containers.
Bellows-shaped shields and double wall instrument carrying cases.

There are three basic blow molding techniques –continuous extrusion, intermittent extrusion and injection blow molding- and numerous variations of each. However, all the blow molding processes consist of five successive stages:

Melting the resin
Forming the parison or preform: The parison is formed by forcing the plastic melt through a die. In injection blow molding, the melt is injected into a mold cavity to form a “test tube” like perform. Multiple performs are usually molded in a single injection cycle.
Transferring the parison or perform: in injection blow molding, there are two basic methods for transferring the performs, the first one directly to the blowing station or indirectly the preforms cool, are ejected and then stored in inventory for subsequent forming in a separate blow molding unit.
Inflating the perform: all of the various blow molding techniques use the same basic process for forming the hollow, high pressure air injected into the hot parison or preform forces out against the inside surfaces of the mold cavity.
Cooling and ejection: after the part is blown it is then cooled rapidly by cooling the die internally with coolant and then opening and ejecting the part with actuated ejector pins that are incorporated in the mold.