Direct Soling Method Using Pre-foamed Sole Material Injection
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Solution Overview
Problem
Existing direct soling methods for manufacturing shoes are inefficient due to long processing times, high costs, and complex equipment requirements, with issues such as temperature drops causing viscosity increases and the need for high-pressure molds and seals, which complicate the connection of soles to uppers.
Innovation Solution
A method involving foaming sole material outside the sole casting mold, injecting it into an open mold, and bringing the upper into contact with the sole material, using a foaming unit to create a lightweight, low-density sole that expands minimally, allowing for a direct and adhesive-free connection without the need for high-pressure seals or complex equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If molding compound is poured through tilting nozzle into open mold using backward movement of nozzle, then sole can be manufactured, but processing time becomes long and temperature drops causing viscosity increase
Solution Approach 1:
The molding compound is pre-foamed in a foaming unit before injection into the mold. This preliminary foaming action reduces the viscosity of the material before it enters the mold, eliminating the temperature drop issue and reducing processing time. The pre-foamed material is ready for immediate injection without requiring slow pouring operations.
Solution Approach 2:
The manual pouring method through tilting nozzle is replaced by an automated injection system. The injection unit automatically injects the pre-foamed molding compound into the mold under controlled pressure, eliminating the slow backward movement of nozzle and significantly reducing processing time.
2Ease of manufacture
If molding compound is injected into mold under increased pressure with CO2 foaming, then sole can be manufactured, but apparatus complexity increases due to need for tight seals and resistant materials
Solution Approach 1:
The injection system is divided into separate functional units: a foaming unit that pre-foams the molding compound, an injection unit that delivers the material, and an open mold. This segmentation allows each unit to operate at optimal pressure levels without requiring the entire system to withstand high pressures, eliminating the need for complex seals and resistant materials throughout.
Solution Approach 2:
The foaming process changes the physical parameters of the molding compound before injection. By pre-foaming the material to reduce its density and viscosity, the injection can be performed at lower pressures than traditional high-pressure CO2 foaming methods, simplifying the apparatus requirements.
3Stress or pressure
If wall thicknesses of molded body or casting mold are increased to withstand increased internal pressure, then high-pressure injection can be performed, but material usage increases and cost rises
Solution Approach 1:
The molding compound is pre-foamed before injection, which reduces its viscosity and allows it to flow more easily into the mold cavity. This preliminary action eliminates the need for high injection pressures, thereby removing the requirement for increased wall thicknesses and reducing material usage.
4Reliability
If suitable seals are provided at complex geometries to withstand frequent method cycles, then high-pressure injection can be maintained, but cost and maintenance effort increase
Solution Approach 1:
The complex sealing system required for high-pressure injection is completely removed by using an open mold design. The mold remains open during injection, and the pre-foamed material is injected without requiring pressure containment seals. This extraction of the sealing requirement eliminates maintenance efforts entirely.
5Temperature
If large drop in temperature occurs during pouring of molding compound, then viscosity increases making connection to lasted upper difficult, but pouring at increased temperature requires increased effort and costs
Solution Approach 1:
The molding compound is pre-foamed in a foaming unit before injection. This preliminary action maintains the material at optimal temperature and reduces viscosity before it enters the mold, eliminating the temperature drop issue during the pouring process and removing the need for increased heating effort.
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 reduces production time and costs, minimizes material expansion, and ensures a stable, lightweight sole attachment, improving manufacturing efficiency and product quality while reducing environmental impact.
Implementation Method 1
foaming sole material outside the sole casting mold
Implementation Method 2
The injected sole material is configured to experience substantially no further expansion
Data Source
AI summary
A method for manufacturing a shoe can include a) lasting an upper; b) providing an open sole casting mold; c) foaming sole material outside the sole casting mold; d) injecting the foamed sole material into the sole casting mold; and e) bringing the lasted upper into contact with the injected sole material.