Two-Stage Press Forming for Curved Flange Angle Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In press forming of products with flange portions curved in a convex or concave manner, springback due to residual stress occurs, leading to inaccurate flange angles and potential tool damage during trimming processes, as existing methods fail to effectively reduce stress without altering the flange angle.
Innovation Solution
A two-process press forming method where the first process forms the top and side wall portions with a side wall height greater than the target shape, and the second process adjusts the ridge between the side wall and flange portions to achieve the target side wall height, thereby reducing residual stress and suppressing springback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the flange angle is changed in forming processes to reduce residual stress, then springback is suppressed, but stress at the distal edge portion markedly changes while stress at the base portion hardly changes, and tool damage risk increases during trimming
Solution Approach 1:
The forming process is divided into two distinct stages: a first forming process that forms the basic shape, and a second forming process that specifically addresses the flange portion. This segmentation allows different forming strategies to be applied to different portions of the workpiece, reducing stress concentration at critical areas while minimizing springback.
Solution Approach 2:
The first forming process performs preliminary shaping of the workpiece, creating a pre-formed state that prepares the material for the second forming process. By performing this preliminary action, the material structure is optimized before the final forming operation, reducing residual stress and springback while maintaining tool integrity.
2Manufacturing precision
If a trimming process is interposed between forming processes, then shape accuracy is improved, but the cutting edge does not contact the workpiece orthogonal to it, causing tool damage
Solution Approach 1:
The pressing member is designed with movable and adjustable characteristics, allowing it to adapt its position and orientation during the forming process. This dynamic adjustment ensures optimal contact between the pressing member and the flange portion, maintaining shape accuracy while preventing tool damage through proper force distribution.
Solution Approach 2:
The position, orientation, and shape of the pressing member are optimized as variable parameters. By changing these parameters, the forming process achieves both high shape accuracy and tool protection, as the pressing member can be configured to match the specific geometry of the flange portion being formed.
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 significantly reduces compressive and tensile stresses in the flange portion, minimizing springback and maintaining the target angle between the side wall and flange portions without altering the flange angle, thus enhancing shape accuracy and preventing tool damage.
Implementation Method 1
a blank (41) is sandwiched between the pad (55) and the lower tool (53) and is curved in a convex manner in the height direction. The portion corresponding to the flange portion (7) is subjected to shrink flange deformation
Implementation Method 2
springback caused by residual stress in the flange portion generated in a process of forming occurs after die release, resulting in no target flange angle being achieved
Data Source
AI summary
A method of press forming that forms a press-formed product into a target shape, the method including: forming a top portion; forming a side wall portion and a flange portion such that a side wall height of the side wall portion of the press-formed product becomes larger than a side wall height of the target shape, where the side wall height of the side wall portion is formed to be larger than the side wall height of the target shape by adding a value half or less of a radius of curvature of the ridge, in a longitudinal direction vertical cross section, of the target shape; and reforming a ridge between the side wall portion and the flange portion such that the side wall height of the side wall portion becomes the side wall height of the target shape.