Physical Foaming Injection with Supercritical Fluid Pressure Staging
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Solution Overview
Problem
Conventional physical foaming injection technologies face challenges in manufacturing high-foam products with complex 3D shapes and achieving weight reduction beyond 10-15%, while the device complexity hinders reproducibility for mass production.
Innovation Solution
A method and system for physical foaming injection involving a barrel with a first screw and a second screw, where gas for foaming is directly provided and converted into a supercritical fluid, followed by controlled pressure reduction in stages, allowing for the production of low-density members with a density range of 0.1 g/cc to 0.5 g/cc.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If conventional foaming technologies are used to achieve weight reduction, then weight reduction of 10-15% is achieved, but it is difficult to manufacture high-foam products with density below 0.1 g/cc
Solution Approach 1:
The patent changes the physical parameters of the foaming process by using supercritical carbon dioxide and controlling temperature and pressure parameters. The resin is heated to melt the beads (150-250°C), then supercritical CO2 is introduced at high pressure (73-300 atm) and temperature (31.3-48°C) to achieve high foamability and produce low-density foamed products with density 0.05-0.5 g/cc
Solution Approach 2:
The patent utilizes phase transitions of carbon dioxide between supercritical, gaseous, and liquid states to control the foaming process. CO2 transitions to supercritical state during injection, then transitions to gaseous state during decompression to form foam, and finally returns to liquid state for recovery, enabling high-foam product manufacturing
2Manufacturing precision
If a complex device structure for manufacturing and supplying supercritical fluid is used, then high foamability is achieved, but reproducibility for mass production is difficult to secure
Solution Approach 1:
The patent employs a multi-functional injection molding device that can perform resin bead melting, supercritical fluid injection, foam formation, and product ejection in a single integrated system. The device handles both thermoplastic and thermosetting resins using the same basic mechanism, and includes features for both high-foam and low-foam product manufacturing, improving reproducibility for mass production
Solution Approach 2:
The injection molding device is divided into functionally independent segments: a heating mechanism for melting resin beads, a supercritical fluid injection system for introducing CO2, a decompression system for foam formation, and a product ejection system. This modular segmentation allows each component to be optimized independently while maintaining overall system reproducibility
3Volume of moving object
If core-back technology is used to mechanically increase the volume of the mold cavity, then thickness of the same shape is increased, but it is limited and difficult to manufacture high-foam products with complex 3D shapes
Solution Approach 1:
The patent changes the fundamental approach from mechanical volume increase to chemical/physical foaming by introducing supercritical carbon dioxide. This allows the resin to expand in-place during molding, achieving high foamability (density 0.05-0.5 g/cc) and enabling complex 3D shapes without being constrained by mold cavity volume limitations of core-back technology
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
Enables the cost-effective and eco-friendly mass production of low-density members, such as shoe soles, with minimized by-products and improved reproducibility, suitable for complex shapes.
Implementation Method 1
manufacturing a melt by rotating and heating the resin beads with a first screw
Implementation Method 2
heating an inside of a barrel that is elongated in one direction
Implementation Method 3
forming a supercritical fluid by agitating a second screw placed in front of a first screw
Implementation Method 4
forming a supercritical fluid by agitating a second screw
Implementation Method 5
providing a mixture in which the supercritical fluid is incorporated into the melt
Implementation Method 6
reducing pressure of the cavity in multiple stages after the injection of the mixture
Implementation Method 7
foaming the mixture in the cavity while injecting the mixture into the cavity
Implementation Method 8
uses supercritical fluid to foam resin without using chemical crosslinking agents
Data Source
AI summary
System and method for physical foaming injection suitable for manufacturing low-density member are provided. The method for physical foaming injection includes i) heating an inside of a barrel that is elongated in one direction; ii) providing resin beads in the barrel; iii) manufacturing a melt by rotating and heating the resin beads with a first screw provided in the barrel; iv) directly providing a gas for physical foaming in the barrel along a transferring direction of the resin beads by spacing the resin beads; v) providing a gas for physical foaming in the barrel and forming a supercritical fluid by agitating a second screw placed in front of a first screw, the first screw to be spaced apart the second screw along a transferring direction; vi) providing a mixture in which the supercritical fluid is incorporated into the melt while the melt passes through the supercritical fluid; vii) pressurizing a cavity formed by the combination of a upper mold part and a lower mold part by injecting gas into the cavity; viii) foaming the mixture in the cavity while injecting the mixture into the cavity; ix) reducing pressure of the cavity in multiple stages after the injection of the mixture, and x) separating the upper mold part and the lower mold part from each other to remove the foamed member with a low density of 0.1 g/cc to 0.5 g/cc.