Blow molding

Enoch Ferngren and William Kopitke produced a blow molding machine and sold it to Hartford Empire Company in 1938.

The technical mechanisms needed to produce hollow-bodied workpieces using the blowing technique were established very early on.

In the United States soft drink industry, the number of plastic containers went from zero in 1977 to ten billion pieces in 1999.

The process of injection blow molding (IBM) is used for the production of hollow glass and plastic objects in large quantities.

This is the least-used of the three blow molding processes, and is typically used to make small medical and single serve bottles.

The injection blow molding machine is based on an extruder barrel and screw assembly which melts the polymer.

The molten polymer is fed into a hot runner manifold where it is injected through nozzles into a heated cavity and core pin.

The end of the core rod opens and allows compressed air into the preform, which inflates it to the finished article shape.

After a cooling period the blow mold opens and the core rod is rotated to the ejection position.

The preform and blow mold can have many cavities, typically three to sixteen depending on the article size and the required output.

There are three sets of core rods, which allow concurrent preform injection, blow molding and ejection.

These "crosses" fit together leaving little space as more surface area is contacted thus making the material less porous and increasing barrier strength against permeation.

In the ISBM process, the preforms are heated (typically using infrared heaters) above their glass transition temperature, then blown using high-pressure air into bottles using metal blow molds.