CNC punching – what is it and how does it work?

CNC (or Computer Numerical Control) punching is a sheet metal fabrication process accomplished by using CNC punch presses. These machines come in two primary designs: single head with a linear rail or a multi-tool turret head. A CNC punch machine is programmed to move a sheet of metal precisely along the x and y axes, positioning it beneath the punching ram to punch holes or form shapes.

Most CNC punch presses can manage sheet metal from 0.5mm to 6.0mm thick and work with various materials, including steel, zintec, galvanised steel, stainless steel, and aluminium. They can punch simple shapes like circles and rectangles or create custom shapes for specific cutouts. Through single hits or overlapping geometries, complex component shapes can be produced.

The machine can also form 3D features like dimples, screw-threaded plunges, and electrical knockouts on either side of the sheet, which are commonly used in sheet metal enclosures.

Some advanced CNC punch machines can tap threads, fold small tabs, and punch sheared edges without leaving tool marks, enhancing productivity within the component cycle time. The CNC program directs the machine to create the desired component geometry.

CNC machines are used in many industries because they can produce high-quality parts with precise measurements and complex shapes. CNC machines have many advantages over manual machining, including:

• High accuracy: They can produce parts with tolerances as low as ±0.02 mm. This makes them ideal for industries like aerospace and medical, where high accuracy is required.
• Consistency: CNC machines can produce identical parts repeatedly, perfect for mass production.
• Speed: They can operate 24/7 without breaks, reducing production time.
• Safety: They are safer than manual machines because they are operated behind a guard.
• Cost: They can be more cost-effective than manual machining because one operator can run multiple machines at once, and there is less material wastage.
• Material range: CNC machines can work with a wide range of materials, including mild steel, zintec, galvanised steel, aluminium, stainless steel, copper, brass, and pre-coated steel.

Turret style CNC punching machine

The turret-style machine holds all the tools in a rotating circular turret, with each tool fixed in a designated position. Three to four rotational tools are in an indexing station, allowing flexible positioning. With access to over 60 tools, this setup enables quick and easy creation of various shapes, from simple to complex. At KMF, all of our Trumpf Punches utilise a multi-tool turret design.

Linear rail style CNC punching machine

In the linear-style magazine, one tool at a time is loaded into the punching head, allowing each tool to rotate fully. This design offers the advantage of quick job setup, with minimal changeover time between tasks.

The designs created by a CNC punch press machine are versatile, ranging from basic shapes like rectangles and circles to custom shapes designed for specific cutout patterns.

Complex sheet metal shapes can be achieved by combining single strikes and overlapping geometries. Some more advanced machines can also tap threads, fold small tabs, and punch sheared edges without leaving tool marks.

Examples of sheet metal fabrications that use CNC punching at KMF include vending machines, power distribution boards, digital signage products and aerospace components.