Mold Vent Hole Design for Resin Foamed Molding
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Solution Overview
Problem
Conventional molds for forming resin foamed moldings face issues with gas exhaustion, leading to defects like underfill or voids, and existing solutions complicate the mold configuration with vent holes and require additional components for gas management.
Innovation Solution
A mold design with a vent hole on the vertical surface of the cavity end portion, equipped with an annexed member having a smaller air passage and covered with air permeability materials like nonwoven cloth, which slows gas escape and prevents resin entry, allowing for controlled foaming and full cavity filling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a vent hole is provided in the forming mold to exhaust gas, then gas exhaustion is improved, but foam resin material is exhausted outside the mold through the vent hole causing material loss
Solution Approach 1:
A non-air-permeability sheet is introduced as an intermediary component between the vent hole and the cavity. This sheet allows gas to pass through while blocking the foam resin material, thus preventing material loss through the vent hole while maintaining gas exhaustion functionality
Solution Approach 2:
The vent hole is positioned at the cavity end portion rather than the cavity main portion. This local positioning ensures that the vent hole exhausts gas from the end portion where gas accumulates, while the non-air-permeability sheet prevents resin from entering this specific vent hole location
2Speed
If the vent hole is directly opened to the atmosphere, then gas flow velocity is high, but the foam resin material moves toward the vent hole and closes it before the cavity is filled
Solution Approach 1:
The non-air-permeability sheet acts as a mediator that modulates the gas flow. It allows gas to escape at controlled velocity while preventing the foam resin material from reaching and closing the vent hole, thus maintaining both gas exhaustion efficiency and complete cavity filling
3Object-generated harmful factors
If the vent hole is provided at the ceiling portion of the mold, then gas exhaustion is achieved, but pins are required for installing the slab or nonwoven cloth resulting in complicated configuration
Solution Approach 1:
Instead of providing the vent hole at the ceiling portion and installing components from above using pins, the vent hole is positioned at the cavity end portion. This inverted approach eliminates the need for pins and simplifies the mold configuration while maintaining effective gas exhaustion
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 solution effectively prevents gas accumulation and resin defects by managing gas flow and ensuring complete cavity filling without material loss or complex configurations, resulting in high-quality resin foamed moldings.
Implementation Method 1
the vent hole is covered at the cavity side thereof with an air permeability material
Implementation Method 2
the foam resin material is foamed and cured. The foam resin material is gradually filled in a cavity while expanding
Data Source
AI summary
Provided is a mold configured to properly exhaust gas from a cavity and to prevent resin from entering into a vent hole, and a method for molding resin foamed molding using the mold. The mold (1) includes lower mold (2), upper mold (4), and core mold (3). The core mold (3) is provided at wall portions (3b), (3c) thereof with respective vent holes (6). Annexed members (7) are detachably attached to the outer surface sides of wall portions (3b), (3c). Each of the annexed members (7) has a tubular shape having an air passage in communication with the vent hole, and a sectional dimension smaller than that of vent hole (6). A nonwoven cloth (10) is attached to core mold (3) so as to cover each surface thereof facing the cavity, and cover wall portions (3b), (3c), thereby covering vent hole (6) from the cavity side.