# Inputs for calculating the Bend Angle Tonnage required
- Material Type: Aluminum or Steel
- Tensile Strength (if known) in Mpa
- Material Thickness in inches, The material thickness plays a significant role in determining the internal radius, especially in air forming where the radius is produced as a percentage of the die opening width. For example, with 0.125-in.-thick material, the minimum inside bend radius is 63 percent of the material thickness, which would be 0.063 in.
- K-Factor
- V die opening (print suggested v opening of 8x material thickness) in inches
The V die opening is typically described by its width and height, but for calculations involving tonnage and bend angles, both the width and height are considered. It affects the tonnage of the press brake, which is the maximum amount of metal that the press brake can handle at once without overheating or damaging the machine. Tonnage calculations take into account the V die opening size to ensure that the press brake can safely accommodate the workload
Width (V-die width): This is the horizontal dimension of the V die opening. It affects the bend radius and the amount of material removed from the radius. The V-die width is used in calculations such as the 20 percent rule, which states that the inside radius produced is equal to a percentage of the V-die opening factored by material type
Height (V-die height): This is the vertical dimension of the V die opening. It affects the tonnage of the press brake and the force required to bend the material. A larger V-die height indicates a greater tonnage requirement, which can affect the strength of the press brake and the time required to complete the bending operation.
- Desired bend radii/radius
When determining the internal radius of a bend, the V die opening is essential. It helps to calculate the internal radius produced by the press brake, which is often a percentage of the V die opening factored by material type. The internal radius is often determined as a percentage of the V die opening width, with the percentage varying depending on the material type. For instance, for 304 stainless steel, it might be 20-22 percent of the die opening.
- Minimum flange dimensions width and length
The V die opening is also used to determine the minimum flange, which is the smallest diameter of the corner radius that can be achieved by the press brake. The V die opening size helps to define the limits of the press brake's capabilities
## Formula for tonnage
{[(575 × Material thickness squared) / Die width] / 12} × Material factor
