Press brake air bending force and tonnage calculator

This is our calculator to calculate the force of press brake necessary for your application.

• Used only for air-bending deformation technique
• Only theoretical values - for more realistic values please use the manual of your press brake or CNC software calculations
• This calculator just for main information - no responsibility for information use and possible problems
• You can use and input manually tensile strength for non-indicated materials
• Recommended die opening V - general sizes available for dies on the market as standard. Sometimes use of customized and special die opening could be more effective
• Parameter Fm - just to indicate force/meter which is important for bending tooling choose

• Calculation of V-die opening (parameter V):
  V=S*6 for thickness less 0,7 mm;
  V=S*8 for thickness 0,71 - 6 mm;
  V=S*10 for thickness 6,01 - 10 mm;
  V=S*12 for thickness 10,1 - 14 mm;
  V=S*14 for thickness from 14 mm and higher
• Calculation of internal radius (parameter R): R = (5*V)/32
• Calculation of minimal flange (parameter h):
  30° - h = 2*V
  45° - h = 1,38*V
  60° - h = 1,06*V
  90° - h = 0,78*V
  120° - h = 0,64*V
  135° - h = 0,60*V
  165° - h = 0,56*V
• Calculation of bending force (parameter F): F = (1,42 * TSS* * (S*S) * L)/(1000*V)
  * parameter TSS = TS/10 (TS - tensile strength)

Minimal flange length is important parameter which should be verified before the bending. With the small flange less than minimal the part could be falled inside the groove of V-die so the minimal flange directly depends of the opening of V-die to stay during the end of the bend on the both shoulders of the die. In some sources it is possible to find the information about the dependance of the minimal flange based on the material thickness (4-5 times as minimal) but such calculation cannot be done without verification of the die size. The smaller flanges as recommended are possible to obtain with roller dies or special tools.
Some sources recommend to determine the material minimal flanges based on the positioning of flat material on the die to the end of the opening + 20% more. So it means for V=50 die the material part after the center of the bending should be 25 (distance from center) + (20% of 50) = 35 mm. We do not recommend this calculation because necessary to considerate also the die shoulder radius for verification.

Internal radius is the parameter to obtain based on the V-die opening size. For development for any sheet metal bending minimal internal radius recommended to project not less than the material thickness. This calculator doesn't show any connection to the radius of the punch (upper tooling) but it is important to note that if the radius of the punch will be bigger than internal calculared radius - the radius of the punch should be considered as obtained. This calculation doesn't work with special materials where the recommendation could be to bend with 1,5-2 times of thickness of the material for internal radius. Moreover special recommendations could be done for aluminium to prevent the cracking of the material.
This calculation is not used for radius bending. For radius bending theoretical formula to be used should be: V-die size (parameter V) = 2*R + 2*S, so to achieve R50 internal radius on the part it is necessary to use V-die not less than 50*2 + 2 of material thicknesses and angle of the die less than ~70 degrees to do the overbending to prevent the springback.