Auto Outer Panel Press Forming for Sharp Character-Lines
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Solution Overview
Problem
Existing press forming methods for automobile outer panels with sharp character-lines suffer from skid line defects due to imbalanced tension during the forming process, leading to noticeable appearance defects and limiting designability improvements.
Innovation Solution
A press forming method and apparatus using elastic bodies on the punch and die surfaces to manage tension imbalances by contacting the metal sheet before the ridgeline, ensuring a controlled friction force that exceeds the tension difference, thereby preventing skid lines and enabling sharp character-line formation without additional processes or specialized equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a punch with a small-radius ridgeline is used to form sharp character-lines, then designability is improved, but skid line defects occur due to imbalanced tension
Solution Approach 1:
The elastic body is caused to protrude from the punch surface before the ridgeline contacts the metal sheet, performing preliminary support action to prevent skid line defects during the subsequent forming process
Solution Approach 2:
The elastic body acts as an intermediary element between the punch and the metal sheet, mediating the contact process by providing preliminary support and friction force to prevent skidding while allowing the ridgeline to form sharp character-lines
2Object-affected harmful factors
If existing prevention methods are used, then skid lines are prevented, but additional processes or specialized equipment are required
Solution Approach 1:
The elastic body serves multiple functions simultaneously: it provides preliminary support to prevent skid lines, generates friction force to control metal sheet movement, and maintains simplicity of the press forming apparatus by integrating into the existing punch structure
Solution Approach 2:
The protrusion amount of the elastic body is optimized to provide sufficient friction force (μP ≥ |F1-F2|) while maintaining a simple press forming process, changing the physical parameter of the elastic body configuration rather than adding complex process steps
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 prevents skid lines and ensures high-quality formation of sharp character-lines on automobile outer panels, enhancing designability without increasing man-hours or requiring additional equipment.
Implementation Method 1
whereby a friction force larger than a difference in tension acting on both sides of the character-line equivalent portion is generated between the elastic body and the metal sheet, so that skidding of the metal sheet is prevented
Implementation Method 2
a punch side elastic body which is caused to protrude from a punch side forming surface portion... and a die side elastic body which is caused to protrude from a die side forming surface portion
Data Source
AI summary
A press forming method includes: moving a die toward a punch; bringing a punch side and a die side elastic bodies into contact with a metal sheet; and press forming the metal sheet, wherein an amount of protrusion of the punch side elastic body is set so that the punch side elastic body: comes into contact with the metal sheet before the punch; and becomes flush at a bottom dead center, and an amount of protrusion of the die side elastic body is set so that: the die side elastic body comes into contact with the metal sheet before the punch; and a product of: a load of the die side elastic body; and a friction coefficient between the die side elastic body and the metal sheet, becomes equal to or larger than an absolute value of a difference between tensions acting on the portions sandwiching a character-line equivalent portion.