How to Address Uneven Wall Thickness in Stretch-Blow Molding

摘要

Among the beneficial properties of PET is its self-leveling ability. This means that as one part of a preform starts to stretch first, the very act of stretching induces strain-hardening, making it tougher to stretch as a result. This forces adjacent parts that were maybe a little cooler to stretch, and in this back-and-forth of stretching and pausing, the preform develops into a bottle that may show as little as 0.001 in. difference in wall thickness around the circumference of a round bottle.