Bending force calculation based on a reference table. Base values are given for σ=420 N/mm²; the result is recalculated automatically for the selected material.
Set the parameters — the result appears automatically
The calculator estimates the force required for air bending sheet metal on a press brake and converts the result into tonnes. This is the value used to select the required press-brake tonnage. The calculation uses the standard air-bending formula: force is directly proportional to the material tensile strength σ, bend length L and the square of sheet thickness t, and inversely proportional to the V-die opening. Because thickness is squared in the formula, it has the strongest effect on the result: doubling sheet thickness increases the required force by roughly four times.
The main value is force in tonnes: a press brake with rated tonnage not lower than this value, preferably with a 20-30% reserve, is sufficient to bend the part in one pass. Force per metre (kN/m) shows the load per unit of table length and is important for long parts. Minimum inside bend radius warns about the risk of cracking when the bend is too sharp. A wider V-die reduces the required force, but increases bend radius and springback, so V is selected as a compromise between available tonnage and the required bend radius.
Air-bending force is proportional to the square of sheet thickness. For example, moving from 3 to 6 mm under otherwise identical conditions increases the required force by roughly four times, not two times.
A typical reference is V ≈ 6-10 sheet thicknesses. For 3 mm sheet this is roughly V20-V24. A narrower die gives a smaller radius but requires more force; a wider die does the opposite.
The actual tensile strength of a metal batch can be higher than the nominal value; tool wear and cold material also add load. A 20-30% reserve protects the press from overload.
No. This is an indicative calculation of force and radius. Springback is compensated by selecting the punch angle, die radius or by overbending during setup on the press.
In coining, the punch forces the material into the die, so the required force is several times higher than the value calculated for air bending. This calculator estimates air-bending force.
The working table length of the press brake must be at least equal to bend length L. Force also grows proportionally with length, so for long parts both tonnage and working length must be checked.