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Preforms molding

PET Resin
Preform molding
Preform design
Preform Animation
Blow Molding
Bottle Design
Reheat stretch blow machinery
Single stage machinery
One stage vs. two stage machinery


The first step in making bottles is to mold preforms (or parisons). The resin pellets are melted, then injection molded to make preforms. A preform has the completely molded neck finish of the bottle, including the screw threads and the pouring edge, but the body is a short tube with one end closed and with wall thickness about 8-12 times thicker than the bottle wall.

In the two-stage process, the preforms are molded in a dedicated high-output system. These preform molding systems typically consist of a high-speed injection unit with a plasticising screw selected for PET, a balanced hot runner, a multi-cavity injection mold with splits for molding the neck finish and ejecting the part, and some means of removing the preforms without damaging them. Often customized part-handling equipment is integrated with the mold operation to reduce cycle times while improving part quality.

Each cavity of the preform mold has a set of components which mold the preform geometry, called a mold stack. A typical stack design is shown below.