According to the relative position of the upper and lower molds in the bending process, the press brakes processing can be divided into two ways: Air bending and press to the bottom bending.
During the bending process, the upper die and lower die of press brakes are not pressed tightly, by adjusting the depth of the upper mold into the lower die opening to get the required bending angle. This kind of bending method called the air bending.
The deeper the upper mold into the lower mold, the smaller the bending angle, the reverse is also true.
Due to the elasticity of the material, also need to consider the use of excessive bending to control the amount of rebound.
The advantage of the air bending is that a smaller number of molds can be used to achieve forming purpose with a variety of angles, and the required processing pressure is small.
In general, the ratio of the thickness B of the material to the V-shaped opening width V of the lower mold can be selected in order to obtain the optimum bending effect:
(1) When the material thickness is below 12.7 mm, B: V is 1: 8;
(2) When the material thickness is 12.7 ~ 22.2mm, B: V is 1:10;
(3) When the material thickness is 22.2 mm or more, B: V is 1:12.
The above three proportions are standard mold ratio, the material is low carbon steel, the material strength is 43.4kg / mm2.
When programming the bending steps, the above parameters can be set in the CNC system, and generate processing program after automatic processing.
Press to the bottom bending
When adopting press to the bottom bending, the sheet metal is pressed between the upper and lower molds to obtain the desired bending angle and elbow radius. It’s generally suitable for medium and large quantities of production, processing plate with the thickness below 2mm. The bending radius is small, bending precision is high, the precision is good.
It should be noted that the pressure of press to the bottom bending is larger than air bending, generally more than 3 times. The angles of the die should adapt to the angle of the plate.
The die ratio, which is the ratio of the sheet thickness B to the lower mold opening distance V is B: V = 1: 6.
>> You can also check out The Ultimate Guide to Press Brake (2018 Updated) to fully understand things about press brake.