Blow-Molded Container Heating for Uniform Walls and Flat Flanges
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Solution Overview
Problem
Existing blow molding methods face challenges in achieving uniform wall thickness and shape conformity, particularly for containers made from polyethylene terephthalate (PET), especially when forming complex shapes with horizontal flanges, and controlling material distribution during the molding process.
Innovation Solution
A method involving non-uniform heating of a preformed puck to different temperatures, securing the puck to a mold with a flange, and using a plunger to stretch the puck within the mold cavity while applying controlled air pressure to conform to the mold shape, ensuring precise control over wall thickness and flange orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If uniform heating is applied to the preformed puck, then the heating process is simple, but wall thickness uniformity and shape conformity deteriorate
Solution Approach 1:
The patent applies different heating temperatures to different regions of the preformed puck. Specifically, the equatorial region is heated to a first temperature while the polar regions are heated to a second temperature that is higher than the first temperature. This local differentiation of heating conditions allows the material to have different degrees of softness in different regions, enabling precise control over wall thickness distribution and shape conformity during the blow molding process.
2Productivity
If higher air pressure is applied to speed up molding, then productivity increases, but material distribution control and shape precision deteriorate
Solution Approach 1:
The patent employs controlled air pressure application during the blow molding process. By carefully regulating the pressure parameters and timing of air introduction, the method achieves optimal balance between molding speed and shape precision. The differentiated heating pattern works in conjunction with controlled air pressure to ensure that the thermoplastic material distributes evenly while conforming accurately to the mold cavity shape, maintaining manufacturing precision even at higher productivity rates.
3Length of moving object
If the preform is stretched deeply into the mold cavity, then container depth is achieved, but material distribution uniformity and wall thickness control worsen
Solution Approach 1:
The patent uses differentiated regional heating where the equatorial region of the preformed puck is heated to a lower temperature and the polar regions are heated to a higher temperature. This creates zones of different material softness that control how the material flows and distributes during stretching. The heated polar regions become more pliable and flow more readily into the mold cavity, ensuring uniform material distribution and consistent wall thickness even when the container is stretched to significant depths.
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 method enables improved control over wall thickness and shape conformity, allowing for efficient production of containers with consistent dimensions and flat flanges, reducing material usage and production costs.
Implementation Method 1
heating a central region of a preformed puck to a first temperature, and heating an annular region surrounding the central region of the preformed puck to a second temperature, wherein the second temperature is greater than the first temperature
Implementation Method 2
heating a preformed puck to a temperature at or above a glass transition temperature of a material of the preformed puck
Implementation Method 3
stretching the heated preformed puck by pressing a plunger into the heated preformed puck and into the mold cavity in a longitudinal direction of the mold cavity
Implementation Method 4
applying pressurized air to the mold so that the heated preformed puck stretches to conform to the shape of the inner wall of the mold cavity
Data Source
Figure 1A~1C
Figure 1D~1F
Figure 2
AI summary
A method for blow molding a container includes heating a central region of a preformed puck to a first temperature, and heating an annular region surrounding the central region of the preformed puck to a second temperature that is greater than the first temperature. The heated preformed puck is arranged at an upper end of a mold cavity of a mold that defines an outer shape of the container. The heated preformed puck is secured to the upper end of the mold cavity. The heated reformed puck is stretched by pressing a plunger into the heated preformed puck and into the mold cavity in a longitudinal direction of the mold cavity toward a lower end of the mold cavity. Pressurized air is then applied to the mold cavity so that the heated preformed puck stretches to conform to the shape of the inner wall of the mold cavity.