Pouch Battery Case Molding for Wrinkle-Free Cup Part Geometry
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Solution Overview
Problem
The existing molding apparatus for pouch-type battery cases often results in an inclined circumferential surface of the cup part due to frictional forces, leading to reduced energy density and potential cracks or pin-holes at the corners, as well as insufficient elongation of the circumferential surface causing buckling wrinkles.
Innovation Solution
A molding apparatus with a die, stripper, and pneumatic or hydraulic pressure system that includes a first punch with a curved surface and a second punch with a planar surface, along with flexible bags to control internal pressure, ensuring even elongation and maintaining corner thickness, thereby minimizing stress concentration and preventing wrinkles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a predetermined clearance is required between the punch and molding space to prevent friction damage, then the pouch film is protected from damage, but the circumferential surface of the cup part becomes inclined and empty space is generated
Solution Approach 1:
The patent introduces a pressing part that applies pneumatic or hydraulic pressure to the pouch film during molding. This allows the punch to contact the pouch film directly without requiring clearance, eliminating the inclination problem while preventing damage through controlled pressure application rather than mechanical friction.
2Productivity
If the punch presses the pouch film directly, then molding efficiency is improved, but stress concentrates at the corner causing excessive elongation and thinning
Solution Approach 1:
The patent modifies the corner geometry of the punch to have a curved surface with a predetermined radius of curvature. This curved surface distributes the pressing stress across a larger area during molding, preventing stress concentration at sharp corners and avoiding excessive elongation and thinning while maintaining molding efficiency.
3Reliability
If the circumferential surface is not sufficiently elongated, then material integrity is maintained, but compressive force causes wrinkles due to buckling
Solution Approach 1:
The patent employs a multi-stage pressing process where the pressing part applies pressure in controlled stages. This dynamic approach allows the pouch film to elongate progressively in the circumferential direction, accommodating the material's elastic properties and preventing sudden buckling that would cause wrinkles while maintaining surface smoothness.
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 ensures a thick corner thickness, prevents cracks and pin-holes, and enhances energy density by maintaining a sharp outer appearance and sufficient circumferential elongation, reducing empty space and improving the battery's energy efficiency.
Implementation Method 1
a pressing part configured to apply a pneumatic or hydraulic pressure to the pouch film so that a portion of the pouch film is elongated into the first space
Implementation Method 2
a pressing part configured to apply a pneumatic or hydraulic pressure to the pouch film so that a portion of the pouch film is elongated into the first space
Data Source
AI summary
A molding apparatus according to an embodiment of the present invention may mold a cup part in a pouch film. The molding apparatus includes: a die on which the pouch film is seated on a top surface thereof and in which a first space recessed from the top surface is defined; a stripper which is disposed above the die to fix the pouch film and in which a second space is defined at a position corresponding to the first space; and a pressing part configured to apply a pneumatic or hydraulic pressure to the pouch film so that a portion of the pouch film is elongated into the first space.