Paper Deep Drawing Wrinkle Control via Dual Blank Holder
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Solution Overview
Problem
Conventional methods for deep drawing paper blanks to form pressed paper pieces often result in wrinkles, which lead to insufficient bonding and potential leakage or sterilization issues in long-term use containers, as the wrinkles create gaps that prevent pharmaceutical agents from reaching all areas and can cause the contents to leak.
Innovation Solution
A method and apparatus that maintain a constant gap between the first blank holder and the die in the outer peripheral region and apply pressure via a second blank holder in the radially inner region, reducing wrinkling by controlling the circumferential compressive stress and fiber direction, thereby ensuring a tight bond without large wrinkles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If deep drawing is performed on paper blank to form pressed paper pieces, then container shape is formed, but wrinkles occur in upright portions along peripheral edge
Solution Approach 1:
The blank holder is divided into two separate blank holders: a first blank holder that applies pressure to the outer peripheral portion and a second blank holder that applies pressure to the inner peripheral portion. This segmentation allows independent control of pressure distribution in different regions, preventing wrinkles while maintaining the desired container shape during deep drawing
Solution Approach 2:
Different pressure conditions are applied to different regions of the paper blank. The first blank holder applies a first pressure condition to the outer peripheral portion, while the second blank holder applies a second pressure condition to the inner peripheral portion. This local differentiation of pressure conditions prevents wrinkles in upright portions while enabling proper forming of the container shape
2Manufacturing precision
If clamping force is applied to outer peripheral portion to prevent displacement, then bonding surface alignment is improved, but wrinkles are reduced in upright portions
Solution Approach 1:
The clamping force application is segmented into two zones: the first blank holder clamps the outer peripheral portion to ensure alignment, while the second blank holder clamps the inner peripheral portion to prevent wrinkles. This segmentation allows both alignment and wrinkle prevention to be achieved simultaneously without compromising bond strength
3Shape
If paper material is gathered together with reduction in diameter during deep drawing, then container shape is formed, but wrinkles occur due to lack of malleability and ductility
Solution Approach 1:
Different pressure conditions are applied locally to different regions of the paper blank during deep drawing. The first blank holder applies pressure to the outer peripheral portion where material gathering occurs, while the second blank holder applies pressure to the inner peripheral portion to prevent wrinkle formation in upright portions, enabling successful container shaping despite paper's limited malleability
Data Source
Figure 1~2(6)
Figure 3~3E
Figure 4A~5E
AI summary
The objective of the present invention is to provide a method of forming a pressed paper piece by deep drawing a sheet of blank that is primarily made of paper in use of a punch and a die, and a production apparatus for implementing the method, whereby no distinguishable wrinkles are formed in upright portions of the pressed paper piece. The method of producing a pressed paper piece according to the present invention, implemented when deep drawing a sheet-like blank that is primarily made of paper in use of a punch and a die, includes maintaining a predetermined gap between a first blank holder and the die in an outer peripheral region of a process portion of the blank and applying a pressure to a radially inner region thereof via a second blank holder, thereby reducing wrinkling by an effect of integrated functions exerted in both regions of the blank.