Steel plate bending is used to create U shapes, V shapes or channel shapes along a level axis in ductile materials such as sheet metal. Common equipment used within this manufacturing process includes brake presses, box and pan brakes and other specialised machine presses. Archetypal products made this way include boxes used for electrical enclosures and quadrangular ductwork.
In the press brake forming process, a workpiece is placed over the die block which presses the sheet to create a desired shape. When bending is complete the material will attempt to spring back towards its initial position; therefore the workpiece must be over-bent in order to achieve the desired angle. The amount of spring back is totally reliant on the workpiece material and the type of bending.
Types of Bending
Primarily, there are 3 different kinds of bending you can perform on a press brake:
• Air Bending
Air Bending – this process works by pressing a punch onto the workpiece and forcing it down into a bottom V-shaped die. This die is mounted onto the press. The punch creates the bend so that the space between the side wall of the V and the punch is larger than the thickness of the workpiece. As this process requires less bend force, it tends to use smaller tools than other techniques. Air bending is extremely flexible, allowing a number of different materials and thicknesses to be bent in variable angles. This process also requires fewer tool changes than other methods, meaning higher productivity.
Bottoming – in this technique, sheet metal is forced against the V opening within the bottom tool. A set amount of space is left between the bottom of the V opening and the workpiece. This method offers more precision and less springback, but a different tool set will be required for every different material, bend angle and thickness.
Coining – in the coining process the top tool forces the material down into the bottom die with 5-30 times the amount of power of air bending. This causes perpetual deformation through the workpiece and there is very little springback, if any at all. This method offers high levels of accuracy.