Unlike cutting, which removes material from a sheet of metal, forming reshapes and reconfigures the material into the desired shape. Sheet Metal Fabrication: Forming processes include bending, stamping, flow forming, drawing and spinning.
Press Bending uses machines such as press brakes to bend sheet metal into U, V and groove shapes. Bending angles vary from 0 to 120 degrees. Thicker sheets are more difficult to bend. Conversely, horizontal bends in sheet metal can be removed from strip workpieces by a process called “debending”.
Fabricators use sheet bending in large sheet metal fabrication projects. It is a simple automated process where the sheet is held in place by counter blades and blank holders. The upper and lower bending blades of the sheet bending machine generate the lateral bending force. The introduction of the Savagnini bending machine in 1977 further automated the bending process and made it less labour intensive.
Stampinghttp://www.mfgproto.com uses a mechanical or hydraulic press with a tool and die. The process is similar to punching, but does not necessarily remove material from the sheet. Punching is suitable for tasks such as stretching, curling, beading, folding and embossing.
Stretching uses a stretcher, English wheel or hammer and a forging die to pull the metal apart. The die simultaneously stretches and bends the sheet, allowing for the drawing of larger profiles from it. In this process, operators clamp the sheet at the edges using clamps attached to slides, which they operate using hydraulic or pneumatic pressure. This applied force stretches the sheet. The tool used in this process is a stretch-forming block (also known as a forming die). It is a solid profiled material against which the sheet is pressed. There are many types of stretching presses, with the most common being the vertical stretching press. It uses a hydraulic ram to raise the die and press it into the sheet placed on the press bed. In contrast, a horizontal stretching press utilizes a fixed press bed with the die mounted on the side, pulling the sheet horizontally around the die using clamps.
Spinning uses a lathe to rotate a sheet of metal as it is pressed against a tool. It is a unique metal forming technique, similar to CNC turning, used to produce round metal parts such as cylinders and cones. Metal spinning is a forming process used to produce axisymmetric parts using a round roller tool formed on a rapidly rotating mandrel to shape and form sheet metal.
Some processes overlap between cutting and forming. One of these processes is sheet expansion, where operators cut multiple slits into a sheet and then stretch it.
