Door Panel Step Drawing to Prevent Wrinkles and Cracking
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Solution Overview
Problem
The formation of stepped portions on automobile door panels with character lines often results in wrinkles or cracking, which deteriorate the appearance and are not suitable for product application, due to the small sandwiching angle and potential material elongation issues during draw forming.
Innovation Solution
A press forming method involving two drawing steps and a finishing step, where the first drawing step forms a first drawn stepped portion with specific curved portions, and the second drawing step forms a second drawn stepped portion with adjusted curvatures and positions, preventing extreme thinning and material elongation, thereby suppressing wrinkles and cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the elongation of plate material is increased during draw forming to suppress wrinkles, then wrinkle occurrence is reduced, but cracking is likely to occur in the stepped portion
Solution Approach 1:
The draw forming process is divided into two separate stages: first draw forming and second draw forming. Each stage forms a different stepped portion with different curvature requirements. This segmentation allows optimization of forming parameters for each stage independently, preventing both wrinkles and cracking
Solution Approach 2:
The first draw forming creates a preliminary stepped portion structure that prepares the workpiece for the second draw forming. By pre-forming the basic stepped shape with appropriate curvature in the first stage, the second stage can focus on refining the geometry without causing excessive elongation or cracking
2Ease of manufacture
If a single draw forming step is used to form the stepped portion, then the process is simple, but wrinkles or cracking occur due to the small sandwiching angle of the character line
Solution Approach 1:
The forming process is segmented into two distinct draw forming steps, each with specific forming parameters optimized for different regions of the stepped portion. This resolves the contradiction by accepting increased process complexity to eliminate defects
Solution Approach 2:
Different regions of the stepped portion are formed with different curvatures and forming parameters. The first stepped portion has one set of curvature characteristics while the second stepped portion has different curvature characteristics, allowing each region to be optimized for its specific geometric requirements and preventing uniform defect formation
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 effectively prevents wrinkles and cracking, improving manufacturing yield by ensuring a satisfactory appearance of the stepped portion on the door panel, even with a character line, by strategically shifting curved portions and controlling curvature and depth in each drawing step.
Implementation Method 1
a first drawing step of forming, by a drawing process, a first drawn stepped portion from a workpiece
Data Source
AI summary
This press forming method includes a first drawing step for forming a first drawn step portion, a second drawing step for forming a second drawn step portion, and a finishing step for completing a stepped portion. In the first drawing step, a first outside curved portion is formed to the outside of a second outside curved portion with respect to an extension region of a character line, and a first parallel portion is formed to the same depth as the drawn depth of a second parallel portion. In the second drawing step, a second inside curved portion having a greater curvature than a first inside curved portion is formed.