About Bending Spring Back
After the bending operation, the elasticity of the pipe material causes the bending to spring back. To compensate for the spring back, you must increase the bending angle and move the bending point forward. When the pipe is released from the bending machine, the bending angle and the bending point spring back to the theoretical value as shown in the following figure:
1. Bending direction
2. Bending point
3. Real bending point
a(n) Bending Angle
A(n) Real bending angle
L(n) Real bending point location
S(n) Spring back
* 
Only the theoretical bending angle is shown on a pipe piece drawing.