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Preform Design

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


Once a bottle design has been finalized, the preform can be selected from available designs or can be custom designed for the new bottle. The best bottle quality and productivity can only be achieved when the right preform is used. A matching neck finish and part weight are necessary but not sufficient – the preform dimensions must be correct for the bottle dimensions and resin stretch ratios. Consideration of the ease of blow molding and preform molding can also have a significant impact on productivity.

These are some of the steps which may be involved in designing a preform.

The preform design process begins with the neck finish, which determines the diameters just under the neck. A bottle typically has a short straight region in this location, which is also transferred to the preform.
The height of the bottle and the Axial Stretch Ratio determine the length of the preform.

The diameter of the bottle and the Hoop Stretch Ratio determine the inside diameter of the preform (or core diameter).
The wall thickness is adjusted to achieve the required part weight. Alternatively, the wall thickness may be decided earlier in the process, since this dimension has the greatest impact on preform molding productivity.

The design of the transition region between the neck straight and the body of the preform is the most subject to variation. Factors may include the shape of the bottle shoulder, the preform mold stack design, and the ability to position lamps to reheat the region in a two-stage blow machine oven.