Two-Stage Press Forming for Sharp Ridgeline Sections
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Solution Overview
Problem
Existing press forming methods face challenges in forming ridgeline sections with small radii of curvature, as they often result in cracks and surface distortion due to elongation and tensile force relief during the two-stage drawing process.
Innovation Solution
A press forming method involving a two-stage process where an intermediate formed body with a larger ridgeline section radius is created, allowing for coincident and non-coincident cross-sectional regions, with the intermediate region projecting outwardly and curving inwardly, to compensate for length insufficiencies and control elongation, thereby preventing cracks and surface distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a two-stage drawing process is used to form a ridgeline section with a small radius of curvature, then the surface distortion is suppressed, but the elongation becomes large and cracks may be generated
Solution Approach 1:
The patent applies preliminary action by forming an intermediate ridgeline section with a larger radius of curvature in the first stage, preparing the material in advance to reduce elongation. The intermediate formed body is designed with specific cross-sectional shapes that project outwardly and curve inwardly, creating a pre-conditioned state that prevents excessive elongation during final forming while maintaining surface quality and preventing cracks.
2Strength
If the second stage forming is performed in a state where tensile force is relieved, then cracks are prevented, but surface distortion may occur
Solution Approach 1:
The patent applies local quality by creating different regions in the intermediate formed body with distinct characteristics. The outside region projects more outwardly while the inside region curves more inwardly, allowing different parts of the material to experience different stress states during forming. This localized differentiation enables crack prevention in critical areas while maintaining overall surface quality.
3Shape
If a ridgeline section with a small radius of curvature is formed directly, then the design requirement is met, but excessive elongation causes cracks
Solution Approach 1:
The patent applies segmentation by dividing the forming process into two distinct stages with different objectives. The first stage creates an intermediate formed body with a larger radius of curvature and specific cross-sectional features, while the second stage achieves the final small radius of curvature. This segmentation allows the material to be prepared in advance, reducing elongation and preventing cracks while still achieving the desired sharp geometry.
Data Source
AI summary
Provided is a press molding method in which a plate material is molded into a target molded body including a ridge section, said method including: a first step for molding an intermediate molded body; and a second step for forming the target molded body from the intermediate molded body. The target molded body and the intermediate molded body have coincident regions where the cross-sectional shapes coincide on both sides of an intermediate ridge section, and an intermediate region where the cross-sectional shapes do not coincide. The intermediate region includes: an outer region in which the intermediate molded body protrudes outward of an edge radius with respect to the target molded body; and an inner region in which the intermediate molded body is curved inward of the edge radius with respect to the target molded body.