Sheet metal forming process

Abstract

A sheet metal forming process and apparatus using both a mechanical forming step and a superplastic forming step. The mechanical forming step includes using a double-action draw die to create a preform. The preform is then transferred to a superplastic forming tool that uses a superplastic forming process to complete the forming process and create a finished workpiece. Using the mechanical forming step enables rapid creation of a preform having a geometry that reduces overall forming time and provides the ability to draw in additional material to reduce part thinning.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]Not Applicable.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates generally to material forming; and more particularly, to a method for forming a metal sheet.[0004]2. Description of Related Art[0005]Various methods are known for forming a metal sheet. One method involves a draw process wherein a punch pulls a portion of the metal sheet through a shaped die. During the process, the metal sheet typically undergoes a reduction or change in the cross-sectional area or wall thickness of the sheet. Such processes are typically limited by the material's ability to be strained past its rupture point. Thus, depending upon the complexity of the part, the forming stresses on the metal sheet during the forming process may result in metal failure or fatigue and correspondingly an unusable or scrap part.[0006]Superplastic forming (SPF) is a process that takes advantage of a material's superplasticity or abilit...

AI Technical Summary

Benefits of technology

[0011]The method includes developing a preform geometry that reduces forming time and improves panel mobility during the gas or superplastic forming cycle by improving the forming aspect ratio, requiring less part or metal stretch to form over small radii and the ability to draw additional material from the binder area to reduce the amount of thinning required to form the part.

Problems solved by technology

Such processes are typically limited by the material's ability to be strained past its rupture point.

Thus, depending upon the complexity of the part, the forming stresses on the metal sheet during the forming process may result in metal failure or fatigue and correspondingly an unusable or scrap part.

Superplastic forming does have a disadvantage in that it normally requires relatively long forming cycle times. Specifically, a conventional SPF process used to manufacture a complex part can require a forming cycle time as high as 30 minutes.

Further, superplastic forming cannot always be used to obtain a complex part in a single step and therefore may require two or more forming steps.

While this die structure and corresponding process is well suited to many applications, the die structure is somewhat complex and may not accommodate forming some aspects of a complex part such as small radii and corners without causing wrinkling during the drawing process.

In addition, such die sets can be somewhat expensive, relatively complex and in some instances, suitable material from the binder area may not be pulled into the die during the draw process.

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