Stretch Forming

In a stretch forming operation, a sheet metal is stretched to yield point in tension and then wrapped over and around the form block (die). This method has the advantage over other forming methods that spring back is either greatly reduced or completely eliminated, since direct bending stress is never introduced. All the plastic deformations occur in the direction of pulling force. Figure 21.25 shows that the jaws grip the work and first stretch and then wrap it around the die. This method avoids most of the friction which somewhat limits the degree of forming obtainable with the moving die.

Figure 21.25 Stretch Forming