Computer numerically controlled (CNC) punching is a sheet metal manufacturing process that is carried out by CNC punch presses. These machines can be either a single head and tool rail design or multi-tool turret design. The CNC punching machine is basically programmed to move a sheet of metal in an x and y direction so as to accurately position the sheet under the machine’s punching ram ready to punch a hole or form.
The processing range for most CNC punch presses is 0.5mm to 6.0mm thick in a range of materials including steel, zintec, galv, stainless steel and aluminium. The choice of hole punched can be as simple as a circle or rectangle right through to special shapes to suit a specific cut out design. By using a combination of single hits and overlapping geometries, complex sheet metal component shapes can be produced. The machine may also punch 3D forms such as dimples, screw thread plunges, and electrical knockouts etc on either side of the sheet, which are often employed in sheet metal enclosure design. Some modern machines may have the ability to tap threads, fold small tabs, punch sheared edges without any tool witness marks making the machine very productive within the component cycle time. The instruction to drive the machine to create the desired component geometry is know as the CNC program.
CNC Programming sheet metal components on a CNC punch press
CNC programming is the computer aided manufacturing (CAM) side of the CAD/CAM cycle. Information about a design may be presented in a 2D format such as DXF or DWG files or a 3D file format. This information is then used to create the flat sheet metal pressing and assign the correct tooling to create the desired component. The software can also be used to establish the most efficient layout of components from a given size of sheet metal, known as the CNC nest. Obviously, the more components that can be produced from a panel of sheet metal the cheaper each CNC punched component will become. Modern software packages such as Radan® can help to automate this process to achieve the maximum yield from a given sheet metal panel. As a designer of components that will be CNC punched, you do not need to know the exact details of how this may be achieved but it may be useful to bare the following in mind when designing a component that is to be CNC punched from sheet metal.