An analysis of forces during three roller bending process

Drums, pressure vessels, windmill towers are manufactured from cylindrical or conical shells. These cylindrical or conical shells are generally formed by bending sheet of required thickness in three roller bending machine, and then welding their edges to form a complete shell. During bending, the forces exerted on the rollers of the machine must not exceed the bending capacity of the machine. It is also desirable that the bending should be done to an extent to utilise the maximum bending capacity. Thus, it is necessary to estimate the forces during bending, so as to maximise the utilisation of bender capacity, without overloading it, to obtain the desired curvature. Analytical models are available for prediction of bending forces with assumptions of constant bend radius. In fact, the radius continuously changes during bending operation which affects the magnitude and the direction of the forces exerted on the rollers. An attempt is made to overcome this assumption using finite element analysis (FEA). Variation in curvature of plate during bending and forces for various bending configuration such as thickness of plate and roller inclinations have been studied using FEA.