Sheet metal pressing is the most common form of sheet metal processing available. Despite this, it is not the only option for design engineers looking for particular manufacturing results.
Production of large, curved sheet metal parts would be prohibitively expensive if standard manufacturing punch-and-die processes were followed. Instead, design engineers should opt to utilize stretch forming.
Stretch forming uses a block or die to deform a metal sheet while the sheet is under tension. This produces parts with a large curvature, such as body panels on aluminum airplanes or cars. Stretch forming requires the product to be placed in sufficient tension to exceed the yield strength of the material in use.
Spinning is where a workpiece is placed on a lathe and rotated against a mandrel. This deforms the material into the desired shape. Spinning is time-consuming and requires skilled operators to accomplish properly. However, stretch forming and spinning require less tooling costs and, as a result, have a financial advantage over stamping for low-volume part runs.
(a) Parts that require bending a sheet about a large radius to produce parts with excessive curvature should be stretch formed.
(b) Parts that are to be formed into shapes such as cylinders, cones, or hemispheres should be spun using either tube spinning or cone spinning.
By keeping these key points in mind, product designers can minimize tooling costs in sheet metal-based product manufacturing by avoiding costlier manufacturing methods in certain scenarios.