Deformation When Bending Long Sheet Metal

Deformation When Bending Long Sheet Metal

The main reason for this problem is that along the whole bending line, the depth of the top punch enter the lower die is not consistent.

Because the pressure mode of general bending machine is pressing at both ends of the sheet  plate, which called 2 cylinders mounted on both sides of machines. the conventional Y1 and Y2 axes. But the deformation resultant force of sheet metal tends to the middle, which will cause the deformation of pressure plate. In the absence of force, you look like the tip of the upper die is a straight line, but once pressed, especially when the material is hard, the bending length is large, and the thickness of the plate is thick, the pressure plate will become an arc. Although the deformation is usually invisible to the eyes, it is enough to have a great impact on the bending quality, especially when bending diffferent angle. Because in air bending, the bending angle determined by the depth of the top punch entering the lower die, and the pressure plate deforms, resulting in the inconsistency of the depth of the upper die entering the lower die, thus affecting the bending angle. Normally, the angle between the two ends is smaller than  the middle part.

If the angle of the same bending line is not the same, the plate will be curved.

Let's talk about how to eliminate this effect. Modern CNC bending machines are usually equipped with compensation devices, called Anti-deflection table or crowning table. Anti-Deflection compensation includes automatic compensation and manual compensation. The principle of automatic compensation is generally in the bending process. When the top punch enters the deepest part of the lower die, the middle part of the lower die table is jacked up with a small pressure cylinder to make the lower table convex, compensate for the deformation of the upper pressure plate. This is the most widely used and simple way of automatic compensation, there are many other ways of compensation. Like Wila Motorized mechanical crowning table.

CNC Hydraulic crowing table for Yawei cnc pressbrake 400T4m


But there is no need or impossibility to use the automatic compensation device on the short worktable or non-CNC bending machine. Generally, manual compensation means that there is an oblique wedge slider on the splint of each clamping upper die. Adjusting the slider can change the height of the upper die and the depth of the upper die entering the lower die, so as to achieve the purpose of adjusting the angle.

Both automatic and manual have their advantages and disadvantages.

Angle control is very important and difficult to operate in bending process, especially for plate with large bending length. It's not really difficult, it's just a bit of trouble. The material itself also has a great impact on the angle. Anyway, with qualified materials and elaborate workmanship, the problems deformation can be completely eliminated.