PET Container Base Recess Structure Against Roll-Out and Sag
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Solution Overview
Problem
Current polymeric containers, particularly PET containers, are prone to base roll-out and sag under increased pressure, which is a common issue in heavyweight applications.
Innovation Solution
The container design incorporates a base with multiple recesses spaced apart about its axial center, formed using a mold assembly with movable protrusions that stretch the base during molding, enhancing localized crystallinity and rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the container base is made heavier to increase strength, then base roll-out and sag are reduced, but material weight increases
Solution Approach 1:
The base is segmented into multiple recesses (typically three) that divide the base structure into distinct regions. This segmentation creates localized strength zones without requiring uniform thickness throughout the entire base, thereby reducing overall material usage while maintaining structural integrity and resistance to base roll-out and sag.
Solution Approach 2:
The recesses create localized variations in base thickness and material distribution, concentrating material where structural support is most needed (at the recess bottoms and surrounding ridges) while reducing material in less critical areas. This local quality approach provides enhanced strength at specific locations without increasing overall container weight.
2Stability of the object's composition
If the base thickness is increased to prevent base roll-out, then structural integrity improves, but manufacturing complexity increases
Solution Approach 1:
The mold assembly incorporates protrusions that pre-form the recesses during the blow-molding process itself, rather than requiring secondary operations. The protrusions are positioned to create the desired recess patterns, and they are retracted before container ejection, allowing the complex base structure to be formed in a single manufacturing step.
Solution Approach 2:
The mold protrusions are designed to be movable, transitioning between extended positions (during molding to form recesses) and retracted positions (before ejection). This dynamic feature allows the mold to create complex base structures while maintaining ease of container removal, effectively managing manufacturing complexity through controlled motion.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design significantly reduces base roll-out and sag, increases material strength, and allows for reduced material weight while maintaining structural integrity under pressure, suitable for pasteurized, refillable, and spirits containers.
Implementation Method 1
The ability of a PET container to maintain its material integrity relates to the percentage of the PET container in crystalline form, also known as the 'crystallinity' of the PET container. Mechanical processing involves orienting the amorphous material to achieve strain hardening. This processing commonly involves stretching an injection molded PET preform along a longitudinal axis and expanding the PET preform along a transverse or radial axis to form a PET container.
Data Source
AI summary
A polymeric container including a finish defining an opening of the container. A body defines an internal volume for storing product therein. A base is at an end of the body opposite to the finish. The base defines a plurality of recesses spaced apart from one another about an axial center of the base.