Forming processes are basically bending or stretching operations in which the thickness of the metal materials do not change. When multiple bends are made with a single die, it is called forming.
There are generally two principles on which forming process is based.
1. Stretching or compressing the material beyond the elastic limit on the outside and inside of the bend.
2. Stretching the material beyond the elastic limit without compression, or compressing the material beyond the elastic limit without stretching.
Sheet metal is stretched to the yield point in tension and wrapped over and around the form block (die). In this process the spring back is completely eliminated because the forming is done by introducing uniform tensile stresses to exceed elastic limit of metal.