PET bottle manufacturing is a highly automated engineering process. In this article, we outline the step-by-step stretch blow molding (SBM) methodology used in our state-of-the-art facility in Varanasi.
Step 1: Preform Production
High-quality raw PET resin chips are heated and molded into test-tube-like shapes called preforms, complete with finished bottle threads. These preforms are lightweight and easy to inspect.
Step 2: Preheating
Preforms pass through an infrared heating tunnel. This softens the plastic without losing its molecular structure, preparing it for expansion.
Step 3: Stretch Blow Molding
The preheated preform is locked inside a custom steel mold. A stretching rod is inserted to pull the preform axially, while pressurized clean air (up to 40 bar) is blown into it, pushing the plastic against the mold walls.
Step 4: Cooling and Ejection
The mold is cooled using water channels, setting the plastic in its final rigid shape. The bottle is ejected, inspected for defects, and packaged for shipping.