Press-Formed Curved Part Restraining Springback Twist
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Solution Overview
Problem
Press-forming methods using high-strength steel sheets face issues with springback causing twist and shape errors, particularly when using different material strengths or varying plate thicknesses, leading to difficulties in achieving the target shape and assembly rigidity.
Innovation Solution
A method involving a forming step with a first estimated angle to introduce reverse twist followed by a restrike step with a second estimated angle to correct springback, using a combination of forming and restrike molds to manage twist angles effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If press forming is performed in one step without giving an estimated angle to a mold, then the manufacturing process is simple, but twist (forward twist) is generated by springback causing shape error
Solution Approach 1:
The press forming process is divided into multiple steps (forming step and restrike step) with different mold angles applied at each step. This segmentation allows the first forming step to use a mold with a first estimated angle to prevent forward twist, while the second restrike step uses a mold with a second estimated angle to correct any remaining twist, thereby achieving both process feasibility and shape accuracy
Solution Approach 2:
The forming step performs preliminary forming with a mold having a first estimated angle that leaves twist in a direction opposite to forward twist. This preliminary action with compensated twist angle prevents the generation of forward twist during springback, and subsequent restrike step corrects the shape, achieving accurate final form while maintaining manufacturing feasibility
2Manufacturing precision
If a mold with a twist angle in one direction is used to perform press forming, then springback twist can be reduced, but it is difficult to set an appropriate twist angle as too small an angle cannot eliminate twist and too large an angle leaves twist in the opposite direction
Solution Approach 1:
The mold twist angle compensation is segmented into two steps: the forming step uses a mold with a first estimated angle to prevent forward twist generation, while the restrike step uses a mold with a second estimated angle to correct remaining twist. This segmentation allows each step to use smaller, more manageable angle corrections rather than requiring one large complex angle
Solution Approach 2:
The mold angle parameter is changed between steps: the forming mold has a first estimated angle while the restrike mold has a second estimated angle. This parameter change allows optimization of twist compensation at each step independently, making the angle setting more manageable and effective compared to using a single large angle
3Ease of manufacture
If the same mold with a conventional twist angle is used for press forming blanks with different material strengths, then the manufacturing process is consistent, but different degrees of springback occur causing variation in the press-formed part
Solution Approach 1:
The forming mold and restrike mold are designed with specific estimated angles that account for the springback characteristics of high-strength steel. This localized angle compensation in the mold design addresses the material-specific springback behavior, allowing the same molds to effectively handle different material strengths by built-in geometric compensation rather than requiring different molds for each material
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 approach significantly reduces springback-induced twist, ensuring the target shape is maintained and allows for consistent manufacturing across varying material strengths and thicknesses without requiring through holes or grooves, enhancing assembly compatibility.
Implementation Method 1
springback is generated by mold release after a mold is moved to a forming bottom dead center, which easily generates twist in the press-formed part
Data Source
AI summary
A method of manufacturing a press-formed part curved in top view and including at least a top portion and a side wall portion continuous from the top portion, the method includes: a forming step of performing press forming by using a forming mold having a first estimated angle, which leaves twist (reverse twist) caused by springback in a direction opposite to twist (forward twist) generated by springback in a case where press forming is performed in one step without giving an estimated angle to a mold; and a restrike step of press-forming a formed part formed in the forming step by using a restrike mold having a second estimated angle.