PET Preform Geometry for Lightweight Container Blowing
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Solution Overview
Problem
The challenge in producing small-sized PET containers, such as water bottles with capacities less than 1 liter, is to achieve optimal mechanical properties and minimize material usage while avoiding issues like overstretching, poor material distribution, and increased energy consumption, given the constraints of current preform design and manufacturing processes.
Innovation Solution
A preform with a specific geometry is designed, featuring a cylindrical neck, a neck ring, and a preform body with tapered segments and controlled thickness and angle parameters, allowing for efficient blowing and reduced material usage, while maintaining mechanical properties and minimizing energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the preform weight is reduced to minimize material usage, then the amount of resin used decreases and cost-effectiveness improves, but the structural strength and mechanical properties of the container deteriorate
Solution Approach 1:
The preform features variable wall thickness distribution with thicker sections (t2 ≥ 1.5mm) in critical zones like the body and thinner sections in less critical areas. This localized variation in material distribution maintains structural strength where needed while minimizing overall resin consumption, resolving the contradiction between material reduction and strength preservation.
Solution Approach 2:
The invention specifies precise geometric parameters including body length (L2 ≥ 15mm), wall thickness (t2 ≥ 1.5mm), and taper angles (α: 5-15°, β: 10-20°) to optimize the balance between material usage and mechanical properties. By carefully controlling these parameters, the preform achieves sufficient strength with minimized resin quantity.
2Manufacturing precision
If the preform geometry is optimized for thin wall containers, then material distribution improves and manufacturing precision increases, but the risk of overstretching and material faults increases
Solution Approach 1:
The invention defines specific parameter ranges including axial stretch ratio (2.5-3.5), hoop stretch ratio (3.5-4.5), and total stretch ratio (10-16) to optimize the blowing process. These controlled parameter variations ensure precise material distribution while preventing overstretching faults, resolving the contradiction between manufacturing precision and product reliability.
Solution Approach 2:
The preform is designed with pre-calculated geometry and thickness distribution before the blowing process. The body length (L2 ≥ 15mm) and wall thickness (t2 ≥ 1.5mm) are predetermined to ensure optimal material flow and distribution during blowing, preventing faults before they occur while achieving precise manufacturing results.
3Weight of moving object
If the preform body diameter is reduced to use less material, then the final container weight decreases, but the energy consumption for blowing increases
Solution Approach 1:
The invention optimizes the preform body diameter and length parameters to achieve a balance between container weight and blowing energy. By specifying body length (L2 ≥ 15mm) and wall thickness (t2 ≥ 1.5mm), the design ensures efficient material distribution that reduces the energy required for blowing while maintaining lightweight container characteristics.
4Quantity of substance
If the wall thickness is reduced to achieve lighter containers, then material usage decreases and cost-effectiveness improves, but the axial load strength and burst strength deteriorate
Solution Approach 1:
The preform implements variable wall thickness with thicker sections (t2 ≥ 1.5mm) in critical load-bearing zones and thinner sections in non-critical areas. This localized material distribution maintains axial load strength and burst strength while minimizing overall material usage, resolving the contradiction between lightweight design and strength requirements.
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
This design results in a lighter final container with reduced energy use, improved quality, and lower manufacturing costs, along with a wider process window for variability and reduced risks of interference during the blowing process.
Implementation Method 1
a preform body, intended to be heated before the blowing operation
Implementation Method 2
the property of PET to be stretched to reach very thin thicknesses
Implementation Method 3
the property of PET to be stretched to reach very thin thicknesses with respect to other thermoplastic materials
Data Source
AI summary
The part under the neck ring (9) of a preform for blowing a PET bottle of predetermined capacity not larger than 75 cl and with a max. material weight of 15 g, is inclined by an angle α less accentuated than normal, max. 17°, which allows to make a preform with a thickness t2 of the wall thinner than 1.9 mm and a thinner inner diameter of the preform body in order to allow a lower stretch ratio starting from a larger preform to obtain the final bottle of predetermined capacity.