When did blow molding start?

The Blow Molding Process

Blow molding is a manufacturing technique used for creating hollow plastic parts. It is also applicable for forming hollow glass shapes, such as bottles. The process consists of various methods, including extrusion blow molding, injection blow molding, and injection stretch blow molding.

The initial phase of the blow molding process involves softening plastic by heating a preform or parison, which is a tube-like segment of plastic with a hole at one end for the entry of compressed air. Once heated, the parison is clamped into a mold where air is blown into it. The inflated plastic material takes the shape of the mold, and after it cools and hardens, the mold opens, ejecting the finished part. Water channels integrated within the mold aid in the cooling process.

History

The principles of blow molding are derived from glassblowing techniques. In 1946, inventors Enoch Ferngren and William Kopitke developed a blow molding machine, marking the start of commercial blow molding. In the early years, the variety and quantity of products made via blow molding were minimal, stalling widespread adoption until later decades. With advancements and increased production rates, the number of diverse products rapidly expanded.

The capability to manufacture hollow objects using the blow molding technique was established relatively early. As glass's fragility posed a challenge, plastic began to replace glass for certain applications. The first mass production of plastic bottles occurred in the United States in 1970. Germany adopted this technology later but has since become a leading producer of blow molding machinery. For instance, the soft drink industry in the US witnessed a remarkable rise in plastic container use, increasing from zero to ten billion units between 1970 and 1990. Today, the production of blow-molded items continues to grow exponentially.

Types of Blow Molding

Extrusion Blow Molding

Extrusion blow molding is characterized by melting plastic and extruding it into a hollow tube known as a parison. The parison is captured within a cooled metal mold, and air is blown into it to form the intended shape, such as a bottle or container. After cooling, the mold opens, allowing for easy ejection of the finished product.

Spin Trimming

Containers frequently have excess material post-molding. Spin trimming addresses this by utilizing a rotating cutting blade to remove the surplus plastic, which can then be recycled. Spin trimmers cater to various materials, including PVC and HDPE. The physical characteristics of different materials can influence the trimming process, with amorphous materials proving more challenging than crystalline substances.

Injection Blow Molding

The injection blow molding (IBM) method serves the production of hollow glass and plastic items in large volumes. This technique involves injection molding a polymer onto a core pin, which is subsequently moved to a blow molding station where it is inflated and cooled. This process, though less common than other methods, is efficient for producing small medical containers and single-serving bottles.

Injection Stretch Blow Molding

Injection stretch blow molding can be categorized into single-stage and double-stage processes. The single-stage method efficiently handles preform manufacturing and bottle blowing within the same machine, optimizing energy use and reducing costs significantly.

See Also

References

Bibliography

For additional reading and resources regarding the functionality and applications of blow molding, consider exploring the latest advancements in plastic extrusion equipment. Whether you're seeking to optimize production processes or learn about modern machine capabilities, the information provided can enhance your understanding of this invaluable manufacturing technology.