Sheet Metal Bending
Sheet metal bending is one step in the long process of manufacturing or fabricating a product. The metal must be formed, cut and finished before it is ready to be used. Bending, along with annealing, cold rolling or welding, is a procedure that applies enough force to change the form of the flat sheet of metal. Aluminum and stainless steel are the two most common metals, however other flexible metals may be used. Important specifications include the size of the sheet metal, its strength and the number of bends needed. Finishing techniques are additional factors to be taken into account when considering sheet metal bending services. Sheet metal bending is used to create forms that continue through other processes to become electrical enclosures, metal cabinets, silos, vehicles, computers, ventilation shafts, tanks and more. Many industries need sheet metal fabrication for their equipment including military, food dispensing, storage, communications, automotive, computer, medical, electronics, aerospace, telecommunication, pharmaceutical, residential and construction.
There are three main ways that sheet metal is bent: air bending, bottoming and coining. Each is similar to the others but the differences come from the final position of the tool and the thickness of the sheet metal. Air bending brings the punch into contact with the sheet metal piece without forcing the metal into the exact shape of the die, or the shaped indentation that will form the bend. The workpiece is bent on the corners of the die and leaves a pocket of air between the bottom of the die and the bottom of the workpiece. After the process, a certain degree of spring back, where the metal flexes back towards its original position, is expected and should be taken into account. In these cases, over-bending is at times necessary to achieve the proper angle. When sheet metal is bent through bottoming, the punch forces the piece to come into contact with the complete surface of the die. With this method, there is hardly any spring back; the punch requires more force and tonnage than with air bending. Coining is very similar to bottoming except that the inner radius of the piece is less than one material thickness. In other words, the measurement of the angle being made is less than the thickness of the sheet metal. When a sheet of metal is bending, its tensile and compressive stresses must be overcome. Metals also stretch slightly lengthwise and may be thinner in areas under stress.
