EVA Foam Bag Support Shell Segmentation for Complex Geometric Forms
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Solution Overview
Problem
The existing process for manufacturing plastic bags using EVA molding is limited to simple geometric forms and cannot produce bags with recloseable upper openings, as the molding process restricts the extraction of the support shell from the mold, resulting in aesthetically limited designs.
Innovation Solution
A process involving hot vulcanization of ethylene vinyl acetate (EVA) foam with sulphur, molded in a dual half-mold setup that allows for the formation of complex shapes by expanding the material during extraction, enabling the creation of semi-rigid support shells with recesses and a recloseable design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If EVA molding is used to manufacture plastic bags, then the production process is simple and low-cost, but the support shell is limited to simple geometric forms only
Solution Approach 1:
The support shell is divided into two separate half-shells that are molded independently and then joined together. This segmentation allows each half-shell to be extracted easily from the mold while enabling the final assembly to achieve complex geometric forms with recesses and protrusions that would be impossible with a single-piece molding approach.
2Device complexity
If a single concave molding chamber is used, then the mold structure is simple, but recloseable bags cannot be produced
Solution Approach 1:
The single molding chamber is segmented into two separate half-molds, each forming one half-shell. This allows the mold structure to remain relatively simple while enabling the production of recloseable bags with complex geometries, as each half-shell can be independently molded and then joined to form the complete recloseable structure.
3Ease of operation
If the support shell is extracted from the mold after molding, then the bag can be removed from the mold, but complex shapes with recesses cannot be formed
Solution Approach 1:
By dividing the support shell into two half-shells molded in separate half-molds, the extraction process becomes simpler as each half-shell can be removed from its respective half-mold without interference from recesses. After extraction, the half-shells are joined together to create the final complex geometric form with recesses and protrusions that interlock.
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 allows for the production of plastic bags with a wider range of shapes and aesthetically pleasing designs, including complex forms and recloseable structures, while maintaining reliability and using low-cost materials.
Implementation Method 1
A process involving hot vulcanization of ethylene vinyl acetate (EVA) foam with sulphur, molded in a dual half-mold setup that allows for the formation of complex shapes by expanding the material during extraction
Implementation Method 2
molded in a dual half-mold setup that allows for the formation of complex shapes by expanding the material during extraction
Data Source
Figure 1~2
Figure 3~5
Figure 6a~6i
AI summary
Process for making a bag, comprising the following operating steps: a step of molding a support shell made of plastic material, by means of injection of ethylene vinyl acetate admixed with sulphur into a shaped molding chamber of a mold, and such molding step comprises a first step of molding a first support half-shell (1) and a second step of molding a second support half-shell (1'); a step of joining the support half-shells (1, 1') by means of fixing means (9); a step of making two lateral handles positioned at the support shell; a step of inserting an object-holding bag (7) within the support shell.