Three differently designed machines are used to obtain the required shape of an originally flat plate. Roll forming results in an open or closed section. Roll bending gives a circular section, truncated cone section or a shape with variable radius. Press braking creates a linear deformation.
Materials with high plasticity are better for forming. High plasticity means that the material more easily withstands sustainable deformation. The material’s ductility is also an important property. Good ductility means that a material can undergo a change of physical form without losing its mechanical properties.
The key to obtaining a high quality bend in steel is to avoid or eliminate all notches in the machine and in the plate to be bent. Notches are crack initiation sites that might trigger cracks. The machine must be well maintained and lubricated. The plate edges should be ground to remove notches, in particular in the case of a large bending deformation. Plate surface notches close to the intended bending line should be removed.
Carefully fill in the plate and machine parameters as requested by the app SSAB BendCalc, run it and it will provide a set of recommendations to apply. To get the best result, adjust the process or parameters if needed.
During the bending operation, the workpiece will be deformed elastically and plastically. When the bending force is released, the elastic deformation will be reversed to zero, thus decreasing the bending angle. The press brake operator must overbend to the bending angle, which is angularly past the required bent angle, thereby compensating for the springback angle.
Provided the available bending force is sufficient and the machine dimensions are compatible with the size of the workpiece, it is up to the operator to run the punch such that the desired bend angle is obtained after release of the load.
The final bend angle depends on:
Machine geometry and settings as well as workpiece properties do have an influence. The punch radius is the dominating parameter. “Trial and error” is the way to get the required bending result.
The bending radius depends on parameters such as:
Use the SSAB BendCalc to calculate the recommended minimum distance. Too short a distance can cause the workpiece to slip and result in serious physical harm. Safety must always come first.
The information in this report is only applicable to SSAB’s products and should not be applied to any other products than original SSAB products.