PET Bottle Bottom Structure for Strength-Weight Balance
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Solution Overview
Problem
Existing PET bottles face challenges in achieving a balance between mechanical properties, weight, and manufacturing efficiency, particularly in terms of mechanical stability, resistance to deformation, and energy consumption during blow molding.
Innovation Solution
A PET bottle design with a specifically engineered bottom structure featuring a dome, coronal arch, annular seat, and radial grooves, optimized by ratios and thickness distribution, enhances mechanical strength and reduces weight while allowing efficient blow molding under standard conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the bottom is increased to improve mechanical strength and stability, then the bottle can better withstand stacking loads and maintain upright position, but the weight of the bottle increases
Solution Approach 1:
The bottom is divided into multiple functional zones with different thicknesses: a first zone with greater thickness for structural support, a second zone with reduced thickness for weight reduction, and a third zone with intermediate thickness. This segmentation allows the bottle to achieve adequate mechanical strength while minimizing overall weight by placing material only where structurally necessary.
Solution Approach 2:
Different regions of the bottom are assigned different thickness qualities based on their functional requirements. The first zone has locally increased thickness to provide structural support and withstand stacking loads, while the second zone has locally reduced thickness to reduce weight. This local differentiation of material properties optimizes the strength-to-weight ratio.
2Productivity
If the blow molding pressure is increased to improve manufacturing efficiency and reduce production time, then the production speed increases, but the energy consumption increases
Solution Approach 1:
The preform is pre-heated to a temperature above the glass transition temperature of PET before blow molding. This preliminary thermal action softens the material, making it more pliable and easier to mold. As a result, the subsequent blow molding process can be performed at lower pressures and with less energy input while still achieving efficient production rates.
3Weight of moving object
If the quantity of plastic material is reduced to decrease weight and cost, then the bottle becomes lighter and more economical, but the mechanical strength and stability decrease
Solution Approach 1:
The bottom is segmented into zones with different material quantities: a first zone with greater material thickness for structural support, a second zone with reduced material thickness for weight reduction, and a third zone with intermediate thickness. This segmentation allows the bottle to use less overall plastic material while maintaining adequate mechanical strength through strategic material placement.
Solution Approach 2:
The material distribution is locally optimized with varying thicknesses in different regions. Areas requiring strength (first zone) receive more material, while areas where weight reduction is prioritized (second zone) receive less material. This local quality variation enables the bottle to achieve lower overall weight without proportionally sacrificing mechanical strength.
4Ease of manufacture
If the bottom structure is simplified to reduce manufacturing complexity, then the production process becomes easier and faster, but the mechanical stability and resistance to deformation decrease
Solution Approach 1:
The bottom incorporates a curved dome shape with a coronal arch and radial grooves that extend from the center toward the periphery. These curved geometric features are integrated into a single mold cavity, allowing the complex stable structure to be formed in one blow molding operation without additional manufacturing steps, thus maintaining ease of manufacture while achieving enhanced mechanical stability.
Solution Approach 2:
The bottom structure utilizes three-dimensional geometric features including radial grooves that create arches spanning across the bottom. These dimensional features distribute stresses more effectively throughout the structure, improving mechanical stability and resistance to deformation while still being formable in a single blow molding process.
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 optimized bottle design exhibits improved mechanical stability, reduced weight, and lower energy consumption, maintaining upright position under pressure and minimizing deformation during palletization, while maintaining high manufacturing efficiency.
Implementation Method 1
The preform is heated to a temperature above the glass transition temperature of PET
Implementation Method 2
Compressed air is blown into the softened preform so that it expands
Implementation Method 3
the PET hardened to a more or less crystalline state
Data Source
AI summary
A bottle having good mechanical properties and lightness due to its bottom design includes a bottom, a body, and a neck. The bottom has a dome, a coronal arch, an annular seat, a side wall, six main radial grooves, five secondary radial grooves situated between the main grooves, each having an end Ev in the arch, and a peripheral end Ep in the side wall. The bottom is such that the ratio Mf/Vuf, wherein Mf is the weight of the bottom and Vuf is the useful volume of the bottom, is less than or equal to 0.050 g/mL and the ratio Ødo/Hdo, wherein Ødo is the diameter of the dome at its base and Hdo is its apex height along an axis Z, is greater than or equal to 4.4. The invention also relates to a manufacturing method and a mold for the bottle.