Expandable Mold Cavity for Foamed Footwear Midsole Control
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Solution Overview
Problem
Current injection molding processes for producing foamed parts, particularly in the footwear industry, lack efficiency and control over parameters such as cell diameter, cell number, and skin thickness, which are crucial for achieving desired properties in foamed materials like thermoplastic polyurethane (TPU).
Innovation Solution
A method and system involving a polymer processing system with a screw in a barrel, a polymeric material delivery system, a blowing agent delivery system, and an expandable mold cavity, where the polymeric material and blowing agent are mixed and injected into the mold, and the mold cavity is expanded to form foamed parts with controlled parameters like skin thickness, cell diameter, and cell number, using specific temperature and expansion control mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional injection molding processes are used to produce foamed parts, then the basic molding function is achieved, but the control over cell diameter, cell number, and skin thickness is insufficient
Solution Approach 1:
The mold cavity is designed to be expandable, allowing the volume to change dynamically during the foaming process. This dynamic expansion enables precise control over cell size and distribution by adjusting the expansion rate and final volume, while maintaining a relatively simple base mold structure that can be adapted for different product requirements.
Solution Approach 2:
The process controls multiple parameters including blowing agent injection timing, injection pressure, mold cavity expansion rate, and temperature profiles. By independently adjusting these parameters, the system achieves precise control over foam characteristics (cell diameter, cell number, skin thickness) without requiring complex equipment modifications.
2Manufacturing precision
If the mold cavity is expanded to form foamed parts with controlled parameters, then the manufacturing precision is improved, but the process complexity increases
Solution Approach 1:
The polymeric material and blowing agent are mixed and injected into the mold cavity before expansion occurs. This preliminary preparation ensures that the foam formulation is ready and uniformly distributed, so that when expansion begins, the foaming process proceeds smoothly and predictably, simplifying the overall manufacturing operation.
Solution Approach 2:
The process maintains continuous control throughout the foaming operation, with the mold cavity expanding continuously while the foam forms and sets. This continuous action eliminates the need for separate steps for foam formation and shaping, making the manufacturing process more efficient and easier to control despite the added precision requirements.
3Manufacturing precision
If blowing agent is injected into molten polymeric material to form foamed mixture, then the foaming capability is achieved, but the control over foaming parameters is insufficient
Solution Approach 1:
The blowing agent delivery system is integrated with the polymer injection system, combining material delivery and blowing agent injection into a single coordinated process. This merging allows precise control over the ratio and distribution of blowing agent within the polymeric material without requiring separate complex delivery mechanisms.
Solution Approach 2:
The system monitors and controls the injection parameters including blowing agent quantity, injection pressure, and timing. By providing feedback control on these parameters, the system achieves precise control over blowing agent distribution and resulting foam structure, preventing over- or under-foaming while maintaining straightforward operation.
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 method produces foamed parts with precise control over skin thickness, cell diameter, and cell number, achieving improved mechanical properties and efficiency in producing foamed parts for footwear applications, such as midsoles, with enhanced compliance and durability.
Implementation Method 1
mixing polymeric material and blowing agent within the polymer processing space to produce an unfoamed mixture
Implementation Method 2
expanding the mold cavity to form the foamed part
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
The invention relates to systems (100) and methods for creating a foamed part. An example method includes providing a polymer processing system, providing a mold (150) having at least one expandable mold cavity (152) in fluid communication with the polymer processing system, mixing polymeric material and blowing agent within the polymer processing system to produce a unfoamed mixture, injecting a volume of the mixture of polymeric material and blowing agent from the polymer processing system and into the expandable mold cavity, and expanding the mold cavity to expand the unfoamed mixture within the mold cavity and form the foamed part.