Physical Foaming Injection with Supercritical Gas for 3D Low-Density Molding
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Solution Overview
Problem
Conventional physical foaming injection methods struggle to produce high-foam products with complex 3D shapes and achieve weight reduction beyond 15%, and the device complexity hinders reproducibility for mass production.
Innovation Solution
A method involving a barrel with a first screw and a second screw, where gas for physical foaming is directly provided and converted into a supercritical fluid, combined with a controlled pressure reduction and multiple-stage injection and evacuation, to produce low-density members with a density range of 0.1 g/cc to 0.5 g/cc.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional physical foaming injection methods are used, then manufacturing simplicity is maintained, but foamability is limited to 10-15% weight reduction
Solution Approach 1:
The injection process is divided into multiple stages: a first injection of non-foamed resin followed by a second injection of foamed resin. This segmentation allows each injection to serve a specific function - the first providing structural base and the second providing foamability - thereby achieving high foamability without requiring complex single-stage equipment modifications.
Solution Approach 2:
The resin is pre-heated to a specific temperature range (80°C to 120°C) before injection to prepare it for foaming. This preliminary heating action ensures the resin is in the optimal state for subsequent foaming during injection, enabling high foamability while using standard injection molding equipment.
2Volume of moving object
If core-back technology is used to increase mold cavity volume, then thickness can be increased, but complex 3D shapes cannot be manufactured
Solution Approach 1:
The injection system dynamically controls the foaming process by adjusting injection pressure, temperature, and the timing of the two-stage injection. This dynamic control allows the resin to adapt to complex 3D mold cavities during injection, achieving both volume increase and shape complexity without mechanical mold modifications.
Solution Approach 2:
The process utilizes parameter changes in the resin state - transitioning from non-foamed to foamed state during injection by controlling temperature and pressure parameters. This enables the resin to fill complex 3D cavities effectively, achieving both volume expansion and shape fidelity.
3Weight of moving object
If high foamability is pursued beyond 15% weight reduction, then low-density members can be manufactured, but conventional methods cannot achieve the required foaming ratio
Solution Approach 1:
The two-stage injection process ensures continuous useful action - the first injection establishes the resin base and the second injection continues the foaming action. This continuity maintains controlled foaming throughout the injection process, achieving precise density control (0.1-0.5 g/cc) and consistent foaming ratio for mass production.
Solution Approach 2:
The process incorporates feedback control through monitoring injection pressure, temperature, and flow rate during both injection stages. This feedback enables precise adjustment of foaming parameters to achieve the target density range and consistent foaming ratio, ensuring manufacturing precision for low-density members.
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 uniform quality through automated processes.
Implementation Method 1
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
Implementation Method 2
reducing pressure of the cavity in multiple stages after the injection of the mixture
Data Source
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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.