No. 38 - Injection Blow Molding

While Plax Corp. and Owens-Illinois Glass Co. made significant contributions to the early development of injection blow molding, the process wasn’t of great commercial significance until the mid-1950s, when Wheaton Plastics Co. launched its first proprietary machine for high-volume production. Wheaton started its development effort in early 1950, working under patent rights granted by Swiss inventor Alfred Borer.

In injection blow, a preform is injection molded and then carried to the next station where it is blown into the finished container. The process enabled the production of smaller and more complicated parts with more detailed and precise neck finishes than were possible with extrusion blow molding. The absence of large amounts of head and tail scrap were added attractions of the new process.

Injection blow opened up the market for small (8-oz or less) pharmaceutical and cosmetics containers. It also made possible 50-cc liquor bottles of PET. Injection blow added speed for large-volume applications. The invention of the reciprocating screw in the late ’50s had a major impact on the development of in jection blow molding because of the added speed it brought to the process.

Wheaton’s first machine, the A300 model, was a three-station unit with a horizontal rotating table. Some of Wheaton’s first commercial applications were polystyrene pill bottles, Fischer-Price toy figures, and Barex acrylonitrile correction-fluid bottles.