Preform: A test-tube-shaped plastic preform with a closed bottom. It already features the final bottle's neck threads and dimensions, while the body section remains in a compact, uninflated state.
Two-step process: In the first step, plastic (typically PET) is molded into a preform using a preform mold on an injection molding machine. In the second step, the cooled preform is transferred to a blow molding machine, where it is heated and inflated with high-pressure gas to conform to the shape of the blow mold cavity, ultimately forming the familiar bottle shape.
The advantages of this process include:
High efficiency: Preform injection molding can be specifically optimized to achieve high-speed production with multi-cavity molds (e.g., 128 cavities).
High quality: It ensures dimensional accuracy and sealing integrity for the neck threads-the most critical functional part of the bottle.
Flexibility: A single preform design can sometimes be used to produce bottles of various final shapes by employing different blow molds.
Therefore, the preform mold serves as a crucial link in the plastic packaging supply chain, bridging the upstream and downstream stages; its quality directly determines the appearance, performance, and cost of the final bottle.