Foam Resin Sheet Vacuum Forming for Thick Mold Adherence
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Solution Overview
Problem
Existing methods for manufacturing foam molded bodies face challenges in accurately shaping thick foam resin sheets, leading to degradation of shaping characteristics and insufficient rigidity due to insufficient softening of the central portion, resulting in poor mold cavity adherence.
Innovation Solution
A method involving the extrusion and dangling of a molten foam resin sheet between molds, followed by sequential reduced pressure suction steps to shape and expand the sheet, creating a sandwich structure with larger central bubble diameters and smaller surface bubble diameters, enhancing foaming at the center and maintaining high accuracy in mold adherence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a foam resin sheet of ambient temperature is softened by reheating with radiant heat, then the foam resin sheet can be shaped, but the central portion of thick foam resin sheets does not soften sufficiently, degrading shaping characteristics
Solution Approach 1:
The foam resin sheet is prepared in a preliminarily formed state with a thickness larger than the final product thickness before the shaping process. This preliminary formation allows the sheet to maintain better thermal properties during subsequent heating and shaping operations, enabling the central portion to soften uniformly without degrading shaping characteristics.
Solution Approach 2:
The invention changes the physical state parameters of the foam resin sheet by controlling its thickness and thermal properties. By using a sheet with larger preliminary thickness, the thermal conductivity and heat capacity are optimized to ensure uniform softening throughout the sheet during reheating, resolving the contradiction between temperature distribution and shaping accuracy.
2Strength
If the thickness of the foam resin sheet is increased, then the rigidity of the molded body improves, but the softening of the central portion becomes insufficient, resulting in poor mold cavity adherence
Solution Approach 1:
The foam resin sheet is prepared in advance with a controlled preliminary thickness that is larger than the final product thickness. This preliminary state ensures that when the sheet is placed in the mold cavity, the entire thickness including the central portion can soften uniformly and adhere properly to the mold, while still achieving the desired final thickness and rigidity after expansion.
Solution Approach 2:
The invention optimizes the thickness parameter of the foam resin sheet by using a preliminary thickness that is strategically larger than the final required thickness. This parameter change allows the sheet to have sufficient thermal mass for uniform softening and mold adherence, while the subsequent expansion process achieves the target thickness and rigidity specifications.
3Volume of moving object
If secondary foaming is performed by suction from both sides under reduced pressure, then thick portions are formed, but the foam resin sheet cannot follow the cavity shape accurately when thick
Solution Approach 1:
The foam resin sheet is prepared with a preliminary thickness larger than the final product before the shaping and expansion processes. This preliminary state allows the sheet to be drawn into the mold cavity accurately while maintaining uniform thickness distribution, and subsequent expansion from this uniform base ensures both volume increase and shape fidelity are achieved simultaneously.
Solution Approach 2:
The invention changes the thickness parameter by using a preliminary sheet thickness that is optimized for the shaping process. This parameter optimization ensures that during vacuum forming, the sheet can conform to the cavity shape accurately, and during subsequent expansion, the final thickness and volume requirements are met while maintaining shape accuracy.
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 the foam resin sheet to accurately follow the mold shape even at thick thicknesses, resulting in a lightweight and high-rigidity foam molded body with a sandwich structure.
Implementation Method 1
a first suction step, a mold closening step, and a second suction step in this order; wherein the first suction step comprises subjecting the foam resin sheet to reduced pressure suction by the first mold, thereby shaping the foam resin sheet to follow a shape of a cavity of the first mold
Implementation Method 2
one sheet of a foam resin sheet formed by extruding and dangling a molten foam resin from a slit
Implementation Method 3
the second suction step comprises subjecting the foam resin sheet to reduced pressure suction by the first mold and the second mold, thereby expanding the foam resin sheet to have the thickness of the gap
Data Source
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AI summary
A method for manufacturing a foam molded body which can allow the foam resin sheet to follow the shape of the cavity of the mold with high accuracy even when the thickness of the foam resin sheet is thick. The method includes the steps of: an arranging step to arrange one sheet of a foam resin sheet between first and second molds, the foam resin sheet being formed by extruding and dangling a molten foam resin from a slit; and an expanding step to expand the foam resin sheet by subjecting the foam resin sheet to a reduced pressure suction in a condition where the first and second molds are closened to provide a gap between the first and second molds, the gap having a thickness larger than a thickness of the foam resin sheet, thereby expanding the foam resin sheet to have the thickness of the gap.