Vacuum Preforming Sheet Metal to Prevent Wrinkling
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Solution Overview
Problem
Existing methods for forming complexly shaped automotive parts like decklids from superplastically or quick plastically formable metal alloys face challenges in preventing thinning and wrinkling, especially in regions requiring significant stretching and forming, such as raised areas.
Innovation Solution
A method involving a preheated sheet metal blank is preformed using a vacuum in a cavity die before being shaped with high pressure over a punch die, ensuring precise preforming and subsequent pressure forming to achieve the desired configuration without excessive thinning or wrinkling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high pressure is applied directly to stretch the blank over the punch die, then the forming speed and productivity are improved, but the blank experiences excessive thinning and wrinkling
Solution Approach 1:
The cavity die preforms the blank by drawing it into a preliminary shape that conforms to the cavity surface before the punch die applies high pressure. This preliminary action redistributes the material and eliminates defects like wrinkles and thinning before final forming, allowing high pressure to be applied safely for improved productivity
2Manufacturing precision
If the blank is preformed using a cavity die before punch forming, then the surface quality and prevention of thinning/wrinkling are improved, but the device complexity and process steps increase
Solution Approach 1:
The cavity die and punch die are integrated into a single forming system where the cavity die performs preforming and the punch die performs final forming in one continuous operation. This merging of functions into a unified tooling system achieves high surface quality without proportionally increasing device complexity
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 method effectively prevents wrinkling and excessive thinning, ensuring high-quality formed parts by controlling the preforming and pressure forming processes, particularly in regions requiring substantial stretching and forming, like raised areas.
Implementation Method 1
A vacuum is applied to the first side of the blank to draw and shape the blank into the cavity die
Implementation Method 2
Gas pressure is then applied to the first side surface of the blank to press the second side surface against the punch die
Data Source
AI summary
Method of preforming and forming a sheet metal article from a preheated blank of sheet metal uses opposing dies including a punch having a punch surface defining a final configuration for the article and a cavity die having a cavity surface defining a preform configuration. The blank is placed between the dies and has a first side surface facing the cavity die and a second side surface facing the punch. A vacuum is applied to the first side of the blank to draw and shape the blank into the cavity die to a preform configuration conforming to the cavity surface. The punch and the cavity die are then closed toward one another and gas pressure is then applied to the first side surface of the blank to press the second side surface against the punch surface to the finish configuration.