For press brake, we will use air bending normally.

As air bending is more frequently used than embossing, the former will be discussed in detail. As an option, your machine can also be fitted with punching equipment.

Calculation of the required force

Air bending is based upon the principle in which a beam resting on 2 supports is subject to the pressure of a tip load. The efforts are located in three points, viz. A, B, and C.

The table lists the forces required to bend a steel plate with st = 420 N/mm2 and length = 1000 mm based on the following formula :

1.42 X L X σ b X t²

F= -------------------------------------

1000 V


in which :

F : presure expressed in kN

L : length of the bending plate, expressed in mm

R : tensile strength of the material, expressed in N/mm2

s : plate thickness, expressed in mm

V : width of the V-shaped die

As a rule the opening of the V-die should equal the thickness of the plate multiplied by factor 8.

V = 8 x s

Consequently, it takes no complicated calculations to determine the quantity of N required to bend any workpiece.

e.g. :      material :                   steel

length :                                 2500 mm

thickness :                             2 mm

tensile strength :                    450 N/mm2

Pressure required  :                2,5x80x2=400 kN

Press brakes used at full load may not be able to bend some workpieces, because :

  1. point A and B of the new die are acute and thus will set up greater friction forces.
  1. the tensile strength of the plate is higher than 400 N/mm2

In practise, the value of these 2 parameters may exceed the theoretical values by 10%.

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