Foamed Molding Pressure Profiling for Void-Free Filling
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Solution Overview
Problem
Existing methods for producing foamed moldings, such as those used in insulating refrigerators, often result in incomplete filling and the formation of air pockets (voids) due to inconsistent foam density distribution, which compromises insulation effectiveness.
Innovation Solution
A method involving a foam-forming reaction mixture with a setting time of 15 seconds to 50 seconds at 20°C, introduced into a mold under variable injection pressure, reducing over time and with an exit velocity between 1 m/s and 5 m/s, ensuring void-free foaming and homogeneous density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the foam-forming reaction mixture is introduced at high injection pressure to ensure rapid filling of the mold, then the productivity is improved, but the foam density distribution becomes inhomogeneous and voids form
Solution Approach 1:
The injection pressure is varied dynamically during the foaming process. The method uses a multi-stage injection pressure profile where pressure is initially high to ensure rapid mold filling, then gradually reduced to allow homogeneous foam expansion and prevent void formation. This dynamic adjustment of injection pressure resolves the contradiction between rapid filling and uniform foam density.
Solution Approach 2:
The method changes the injection pressure parameter over time during the foaming process. By implementing a time-dependent pressure reduction strategy, the system transitions from high-pressure rapid filling to low-pressure controlled expansion, thereby achieving both high productivity and homogeneous foam density distribution.
2Manufacturing precision
If the injection pressure is reduced to achieve homogeneous foam density, then the manufacturing precision is improved, but the filling time increases and productivity decreases
Solution Approach 1:
The injection process is divided into periodic stages with different pressure levels. The method implements a structured sequence: initial high-pressure injection for rapid filling, followed by intermediate pressure reduction phases, and final low-pressure completion. This periodic pressure variation ensures homogeneous foam density while maintaining overall short processing time.
Solution Approach 2:
The method performs preliminary high-pressure injection to quickly fill the mold cavity, then subsequently reduces pressure for controlled foam expansion. This preliminary action approach allows the system to achieve rapid filling first, then corrects the density distribution in later stages, thereby maintaining both productivity and manufacturing precision.
3Manufacturing precision
If a special nozzle with adjustable opening cross-section is used to reduce exit speed, then the foam expansion is controlled and voids are reduced, but the device complexity and conversion costs increase
Solution Approach 1:
The method replaces the mechanical complexity of adjustable nozzles with a control system that varies injection pressure over time. Instead of modifying the physical nozzle structure to control exit speed, the system uses temporal pressure variation to achieve the same effect of controlled foam expansion and reduced void formation, thereby simplifying the hardware while maintaining manufacturing precision.
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 approach allows for rapid, void-free foaming of complex geometries, enhancing insulation performance by achieving a finer pore structure and uniform bulk density distribution, thereby improving the thermal insulation of hollow bodies.
Implementation Method 1
introducing a foam-forming reaction mixture into the mold
Implementation Method 2
the variable injection pressure in step B) is reduced over time
Data Source
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AI summary
The invention relates to a method for producing foamed molded bodies, comprising the steps of A) providing a mold and B) introducing a foam-forming reaction mixture into the mold, the foam-forming reaction mixture being introduced into the mold under variable injection pressure. The method is characterized in that the foam-forming reaction mixture has a setting time of ≥ 20 s to ≤ 60 s.