A punch press is a machine used to change the shape of metal, specifically to form and to cut it. Usually, a piece of metal is passed through the press. The machine clamps down on the metal and cuts or forms it to a predetermined shape.
In some cases, the punch press may cut and eject the metal piece in just one station. Other pieces may require several stations in order to be completely formed or cut. In this case, the process is called a progressive die, because each station progresses the part one step further toward completion. A punch press can be a simple, small machine that is manually operated, or it may be very large, complex, and operated by computer numerical control (CNC). In this case, a computer is programmed to operate the press.
With both small and large punch presses, a die set is used to help complete the task, though the die set used in a large machine may be a bit more complex. A die set consists of male punches and female dies. When these are pressed together, the metal piece is shaped or cut into the desired form. Both large and small press designs require a craftsman to design the die set and to prepare the machine for operation.
Setting up the punch press can be somewhat time consuming. Nonetheless, it is used for high volume production, with cycle times measured in the number of parts created per second. After the machine is set up, a low-skilled operator can easily monitor its progress and continued operation. In fact, one operator can usually monitor several operations at a time. Therefore, this is a cost effective method for forming metal.
The capabilities of the punch press are described in accordance with its tonnage. A ten-ton press is considered a small unit, while a 60-ton one is commonly used in metal processing industries. Determining the tonnage required for specific jobs is generally simple, as certain materials require a specific tonnage to process.