Sheet Material Forming via Stretching and Dragging
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Solution Overview
Problem
Existing methods for forming three-dimensional products from sheet materials, such as papery materials, face limitations in cavity depth and surface creases, which restrict shape complexity and hinder printing or decoration, especially when using materials with poor extensibility like composite materials with plastic films or embossed aluminum.
Innovation Solution
A forming method that alternates between stretching and dragging steps using a combination of mechanical punches and deformable membranes to shape the material, allowing for deep cavity molding without visible creases, utilizing materials with at least 5% extensibility and incorporating techniques like pneumatic deformation and pre-treatment to enhance shape complexity and printing compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If the material sheet is retained along the edge of the mould cavity during forming, then the extensibility of the material is utilized and it is stretched, but as the cavity depth increases, the degree of extensibility required increases which presents natural limitations
Solution Approach 1:
The forming process is divided into multiple sequential steps (first forming step with retaining, second forming step without retaining) to distribute the deformation requirements. This segmentation allows each step to operate within material extensibility limits while achieving greater overall cavity depth than a single step could provide.
Solution Approach 2:
The first forming step performs preliminary deformation by retaining the material along the cavity edge and stretching it partially. This preliminary action prepares the material for the second step, reducing the extensibility demand in subsequent operations and enabling deeper cavities to be formed without exceeding material limits.
2Shape
If the material sheet is freely dragged into the mould cavity during forming, then the extensibility limitation is avoided, but the dragging results in the formation of visible creases on the container surface
Solution Approach 1:
The forming process is divided into two sequential steps: first forming with retaining (producing fewer creases) and second forming without retaining (achieving deeper deformation). This segmentation distributes crease formation to less critical areas and stages, allowing post-processing or acceptance of creases only in non-printing zones.
Solution Approach 2:
The method allows different regions of the material to experience different forming conditions. Areas that will be printed or decorated undergo forming with retaining to minimize creases, while other areas can be freely dragged into the cavity. This local differentiation of forming quality resolves the contradiction between depth achievement and surface appearance.
3Reliability
If composite materials comprising paper and plastic film with poorly extensible crystalline layers are used, then barrier properties are improved, but the degree of extensibility decreases limiting cavity depth
Solution Approach 1:
The multi-step forming process segments the deformation into manageable portions. The first step with retaining performs gentle preliminary stretching that does not exceed the low extensibility threshold of crystalline plastic layers. The second step completes the forming by dragging material into deeper cavity regions, achieving both hermetic bonding in critical areas and deep shaping overall.
Solution Approach 2:
The process changes the physical state parameters of the composite material during forming. By controlling moisture content, temperature, and pressure in different steps, the material's extensibility is temporarily enhanced during forming operations while maintaining hermetic bonding properties. This parameter control allows deep cavity formation in materials that would otherwise be too rigid.
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
Enables the production of three-dimensional products with virtually no surface creases and unrestricted cavity depth, maintaining printability and hermetic bonding, while allowing for precise control over crease localization and distribution.
Implementation Method 1
a first step in which an extensible material, with a degree of extensibility of at least 5%, is stretched by a movable male die or punch until it has been partially deformed within a female mould provided with a cavity
Implementation Method 2
Given the plasticity of the papery material, the final result obtainable, independently of the method used, is always to stably deform the paper sheet
Implementation Method 3
another known system uses an elastic membrane, which is subjected to pressure until it adheres to the inner surface of the cavity and causes the sheet of papery material to also adhere thereto
Implementation Method 4
another known system uses an elastic membrane, which is subjected to pressure until it adheres to the inner surface of the cavity
Data Source
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AI summary
A forming method for materials in sheet form, particularly papery materials, characterised in that after laying a sheet of material extensible to at least 5% on a mould cavity, the sheet is subjected to at least partial stretching within the mould, while at the same time being retained along the edge of said cavity, and in addition the sheet is subjected to at least partial dragging within the mould without it being retained along the edge of said cavity, independently of the order in which the two aforesaid operations are carried out and independently of any partial overlapping of said operations.