Press Forming of Sharp Ridge Lines Without Scratches or Wrinkles
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Solution Overview
Problem
Conventional press forming methods face challenges in forming ridge line portions with small radii of curvature, particularly when the dihedral angle between flat portions is reduced, leading to increased elongation and potential scratches or wrinkles due to interference with the upper die and local elongation at the boundary between the product and discarded portions.
Innovation Solution
A two-stage press forming method where the intermediate formed body includes a separation portion spaced apart from the upper die to provide elongation allowance for the discarded portion, and a contact portion that comes into contact with the upper die to prevent movement and excessive material supply, thereby preventing local elongation and wrinkles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the slack portion is increased to provide elongation allowance for forming the ridge line portion with small radius of curvature, then the ridge line portion can be formed without cracks, but the intermediate formed body interferes with the upper die causing scratches on the formed product
Solution Approach 1:
The discarded portion is divided into two functional segments: a separation portion spaced apart from the upper die to provide elongation allowance, and a contact portion that comes into contact with the upper die to prevent excessive material supply. This segmentation allows each portion to fulfill its specific function without causing harmful effects.
Solution Approach 2:
Different regions of the discarded portion are given different spatial configurations relative to the upper die. The separation portion is positioned to be spaced apart to enable material elongation, while the contact portion is positioned to contact the upper die to control material flow. This local differentiation resolves the contradiction between needing slack for elongation and preventing interference with the upper die.
2Object-affected harmful factors
If the height of the step portion at the boundary between product portion and discarded portion is increased to prevent interference with the upper die, then scratches are prevented, but local elongation occurs at the boundary causing wrinkles
Solution Approach 1:
The discarded portion is segmented into a separation portion and a contact portion. The contact portion specifically addresses the boundary region by contacting the upper die to prevent excessive material supply and local elongation that causes wrinkles, while the separation portion provides the necessary elongation allowance.
Solution Approach 2:
The contact portion is specifically positioned at the boundary region between the product portion and discarded portion to provide localized control over material flow. This localized contact prevents excessive material supply at the critical boundary area, preventing wrinkles while allowing other regions to have the necessary slack for elongation.
3Shape
If the dihedral angle between flat portions is reduced to achieve sharper ridge line portions, then the design quality is improved, but the elongation of the ridge line portion increases requiring larger elongation allowance
Solution Approach 1:
The separation portion is prepared in advance with sufficient slack to provide the necessary elongation allowance before the actual forming of the sharp ridge line portion. This preliminary preparation of material allowance enables the subsequent formation of sharp ridges with small dihedral angles without causing cracks due to insufficient elongation capacity.
Data Source
AI summary
A press forming method includes a forming step of pressing an intermediate formed body including an intermediate ridge line portion with a large edge radius, into a target formed body. An upper die includes an upper die step portion at a boundary portion between a product portion and a discarded portion. The discarded portion of the intermediate formed body includes a separation portion which is spaced apart from the upper die at an initial stage of the forming step, to provide an elongation allowance for the discarded portion, and a first contact portion and a second contact portion which are brought into contact with the upper die at the initial stage of the forming step, to prevent occurrence of wrinkles.