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Punching is the process of removing material from a sheet of metal by applying a shearing force. A punch press is the machine used for this process. Nowadays CNC punch presses come in all shapes and sizes but generally work the same way using a punch and die. A shaped punch is forced into the sheet of metal and through a die beneath the sheet of the same shape. This process forces the material through the die resulting in a shape being cut into the metal sheet. All of this happens in less than a second and modern CNC punch press machines can operate in upwards of 1000 ‘hits’ per minute.
Laser cutting is a process that uses a thin, focused laser beam to burn through metal sheets. The laser beam moves on an X and Y axis allowing any shape to be cut into a sheet of metal. Laser cutting machines also have etching features where the beam is reduced in power to etch lines and markings onto sheets instead of burning all the way through.
CNC punch press machines were the first to appear in fabrication shops and are still widely used today. Before laser cutting, this was the most common method of cutting parts out of metal sheets with most machines capable of working with material up to at least 6mm in thickness. Over the years, laser cutting has become increasingly faster and more efficient meaning the two processes are comparable, and each one offers a set of advantages and disadvantages.
When it comes to fully perforated sheets with small holes, punching is still the fastest and most cost effective process. For cutting basic shapes and contours, modern day laser cutting machines run at a much faster rate. For each hole shape and size, a punch machine requires tooling to be assembled and setup in the machine which can be very time consuming and inefficient for one-off parts and components.
Modern laser cutting machines can work in sheet thicknesses in excess of 30 millimetres. Most punching machines are limited to 6-8 millimetres in sheet thickness. On the other hand, punching machines can be used for a variety of components due to the tooling available. Up-forms for anti-slip flooring and louvres are both excellent examples of where a punch press machine comes into its own. Door hinges and cheese graters are also manufactured using a punch press.
21st century laser cutters are extremely efficient on both electricity and gasses meaning the running costs of both processes are very similar. Both processes are subtractive methods of manufacturing where the raw material is cut from the source leaving a certain degree of waste. The punch press method works using a set of clamps which grab the sheet of material and move it around under the tool which punches each hole. On the other hand, the material sits in one place on the laser machine whilst the laser beam moves and does all the work. Punching machines therefore need extra space on the sheet of the material for the clamps to hold the sheet. Depending on the brand of machine and type of clamp, up to 100 millimetres of free space is sometimes needed on the bottom of a sheet when punching, whereas a laser cutting machine can work all the way up to the edge. This makes laser cutting more efficient on material utilisation.
