Press-Formed Blank Flange Folding to Suppress Springback
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Solution Overview
Problem
Existing press-forming methods face challenges in suppressing springback, especially in low-rigidity parts, as they often result in defective welding and degraded appearance quality due to elastic recovery from uneven residual stress, and previous methods are insufficient for parts with varying stress states or lacking edge flanges.
Innovation Solution
A press-forming method that involves folding the flange of excess material to form straight sides, creating a bent flange portion with an L- or Z-shaped cross section, which is then extended in the second pressing step to provide bulging, thereby reducing material inflow and enhancing rigidity, and includes a trimming step to form a final product shape without distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-strength steel sheets are used to increase strength and rigidity, then collision protection and fuel efficiency improve, but springback increases causing defective welding and degraded appearance quality
Solution Approach 1:
The patent applies preliminary action by forming an intermediate product with specific geometric features (emboss in stretch flange portion, excess bead in shrink flange portion) before final forming. These pre-formed features create stress distribution that counteracts springback during subsequent forming operations, allowing high-strength materials to be used without sacrificing dimensional accuracy.
Solution Approach 2:
The patent changes geometric parameters by introducing emboss and excess bead features with specific dimensions and locations. The emboss has a depth of 5-20mm and the excess bead has a height of 3-10mm, creating controlled stress states that compensate for material springback behavior in high-strength steel sheets.
2Productivity
If conventional press-forming methods are used, then production efficiency is maintained, but springback causes defective welding and degraded appearance quality
Solution Approach 1:
The patent segments the forming process into multiple stages: first forming an intermediate product with emboss and excess bead features, then performing final forming operations. This segmentation allows independent optimization of stress distribution (intermediate product) and final geometry (final product), maintaining productivity while improving dimensional accuracy.
Solution Approach 2:
The intermediate product serves as an intermediary form between the flat blank and the final product. It contains pre-formed emboss and excess bead features that act as stress mediators, creating a favorable stress state for the final forming operation and reducing springback in the final product.
3Manufacturing precision
If existing springback measures are applied, then some residual stress unevenness is reduced, but low-rigidity parts still suffer from springback and may develop new springback forms
Solution Approach 1:
The patent applies local quality by placing emboss and excess bead features at specific locations corresponding to stretch and shrink flange portions. These localized features create targeted stress compensation in critical areas, making the method effective for low-rigidity parts while maintaining versatility across different part geometries.
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
The method effectively suppresses springback, improves shape accuracy, and increases material yield by controlling the inflow of material during bulging, resulting in a press-formed product with reduced distortion and higher processing precision.
Implementation Method 1
by bending and unbending resistance of the folded portion
Data Source
AI summary
A method for manufacturing a press-formed product includes a blanking step of blanking from a sheet-shaped material into a shape in which an excess material portion is added to the contour outline of a developed shape of the press-formed product, a first pressing step of folding the excess material portion to form straight sides into an intermediate formed product with a bent flange portion, a second pressing step of performing press forming including bulging in which the bulging portion is provided on the intermediate formed product, and a trimming step of trimming the excess material portion. A blank material includes excess material portion to be folded to form straight sides circumscribed around or spaced apart from a contour outline of a developed shape of the press-formed product, and an intermediate formed product includes excess material portion including a bent flange portion folded to form straight sides.