Sheet Bending with Press Brake
Different kinds of machines are employed for sheet metal forming tasks in industries like lathe, sheet bending, power press, press brakes etc.
It is a special kind of sheet bending machine that is designed to meet tougher metal bending requirements in industries. It applies direct strain about the metal sheet and alters it to the desired form. It is commonly utilized all over the entire world to mold all types of metals into different designs. Aluminum, brass, copper, steel, tin, nickel and titanium are some common metals which can be bent into desired shapes using a press brake.
To bend metal using press brake it is first of all inserted in the jaws of press brakes. It is placed between the two tools of machine called punch and die. Punch is the upper tool which exerts force on metal sheet and bends it, while the die is the lower tool of the machine having a specific design. It is in this design that the metal will be casted. For bending, the sheet is placed on the die and held in place by the back gauge while the punch lowers and forces the sheet to bend according to shape of the die. Once this is done, in normal cases the sheet tries to regain its normal position because of the residual stresses acting on it and therefore the sheet is usually over-bent to achieve a proper bend angle.
There are basically three basic types of bending performed using a press brake; air bending, bottoming and coining. In air bending, material is formed by pressing a punch into the material into a bottom V-die. Disadvantage of this method is that it is not as precise as other methods and stroke depth must be kept very accurate. Variations in the thickness of the material and wear on the tools can result in defects in parts produced. Bottoming is similar to air bending. Here also the sheet is forced against the V opening in the bottom tool but the advantage of this method is that it provides greater accuracy and less spring back than air bending. A different tool set is needed for each bend angle, sheet thickness, and material and therefore in general, air bending is the preferred technique in this case. The third process is coining in which the top tool forces the material into the bottom die with five to 30 times the force of air bending. It causes a permanent deformation through the sheet with very little or approximately no spring back at all. This means that with coining high precision can be attained but due to its higher costs it is not often used.
To perform bending, today different ranges are available in the market. Depending on the type of force used for bending, there are 4 different type of brakes; mechanical, pneumatic, hydraulic, and servo-electric. Depending on accuracy, speed and quantity of bending to be performed, one can select the best one for their applications by considering factors like work pieces to produce, inner radius required, accuracy, tooling, flange width etc.