Reverse Press Forming of Curved Panels Without Wrinkling
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Solution Overview
Problem
Existing methods for manufacturing press-formed articles with varying vertical wall heights and curved shapes in automobile body components often result in wrinkling or increased manufacturing costs due to the need for multiple press formings or modifications in tooling.
Innovation Solution
A manufacturing method and apparatus that utilize a single press forming process with vertically reversed tooling, where the metal sheet is held between a pad and punch in one step and between a die and blank holder in another, ensuring no wrinkling occurs by maintaining a vertically-reversing cross-sectional angle of 0° to 80°.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a high strength steel sheet is press-formed using normal drawing or pad bending processes to achieve varying vertical wall heights, then the required strength is improved, but wrinkling or cracking occurs in the press-formed article
Solution Approach 1:
The patent applies reverse forming by inverting the vertical wall direction during press forming. The forming process creates an inverted configuration where the vertical walls are formed in the opposite direction, which prevents material instability and surface defects while maintaining high strength properties. This inversion approach fundamentally changes the forming mechanism to avoid the wrinkling and cracking issues that occur in conventional forming processes.
2Shape
If multiple press formings or component divisions are performed to manufacture press-formed articles with curved shapes and varying wall heights, then the desired shape is achieved, but manufacturing cost increases
Solution Approach 1:
The patent merges multiple forming operations into a single press forming process. By integrating the formation of curved shapes and varying vertical wall heights into one unified forming operation, the need for multiple separate press formings or component assemblies is eliminated, thereby reducing manufacturing cost and process complexity while achieving the desired complex geometry.
Solution Approach 2:
The reverse forming mechanism enables the creation of complex curved shapes with varying wall heights in a single operation. The inversion approach allows the forming process to naturally accommodate geometric variations without requiring multiple forming steps, as the reversed forming direction facilitates material flow and shape development in a unified process.
3Ease of manufacture
If the thickness of the steel sheet is increased to compensate for reduced strength, then the formability is improved, but the weight and cost of the press-formed article increase
Solution Approach 1:
The patent changes the forming process parameters by implementing reverse forming, which fundamentally alters the material deformation behavior. This parameter change enables the use of thinner high-strength steel sheets while maintaining formability, as the reversed forming mechanism improves material flow and reduces forming resistance, thereby avoiding the need to increase sheet thickness for weight and cost reasons.
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 press-formed articles with curved parts and varying vertical wall heights without wrinkling, achieving a tensile strength of 400 MPa or more in a single forming step, reducing manufacturing costs and complexity.
Implementation Method 1
the bent region of the intermediate formed article is bent back in the opposite direction, thereby causing work hardening in the vertical walls of the press-formed article
Data Source
Figure 1A
Figure 1B~1C
Figure 2A~2B
AI summary
The manufacturing method includes a first step in which a pad holding state is established and a second step in which pad draw forming is performed after the first step is completed. In the pad holding state, (a) a part of a blank 15 to be formed into a top plate 21 is held between a pad 13 and a punch 11, and a part of the blank 15 to be formed into a flange 25 is held between a die 14 and a blank holder 12, (b) in a specific press directional cross section of a part of the blank 15 to be formed into a first part, the position of the contacting surface of the blank holder 12 that makes contact with the blank 15 in the direction of pressing is located toward the punch 11 in the direction of arrangement of the pad 13 and the punch 11, compared with the position of the contacting surface of the pad 13 that makes contact with the blank 15 in the direction of pressing, (c) a vertically-reversing cross-sectional angle is more than 0° and equal to or less than 80°, and (d) in a press directional cross section that is different from the specific press directional cross section, the position of the contacting surface of the pad 13 that makes contact with the blank 15 in the direction of the pressing is located toward the pad 13 in the direction of the arrangement, compared with the position of the contacting surface of the blank holder 12 that makes contact with the blank 15 in the direction of pressing.