Laser cutting is essentially a thermal process, where a material is melted in a particular area using a laser beam. There are essentially 3 kinds of laser cutting – remote cutting, flame cutting and fusion cutting.
Types of Lasers
These days, sheet metal is cut in industries usually using two kinds of lasers i.e. Co2 laser and fibre laser.
In the past, sheet metals were commonly cut using CO2 lasers. The CO2 laser or the carbon dioxide laser is basically produced in a gas mixture that mostly consists of helium, carbon dioxide (CO2) and nitrogen. This type of laser is pumped electrically by making use of an electric discharge.
Typically, CO2 lasers are produced at a 10.6μm wavelength and the lasers that are used for processing material usually generate laser beams that have several kilowatts of power. CO2 lasers can be used to cut thick materials that are more than 5mm and it is a quicker cutting process compared to a fibre laser. When cutting thicker materials, CO2 lasers also produce a smoother cutting-edge and superior surface finish. Most of the CO2 laser cutting systems are 3-axis systems i.e. X-Y, 2-dimensional position control and a Z-axis, which is the height control.
These kinds of lasers basically belong to the family of “solid-state type lasers”, where the laser beam is produced by a solid substance. Fibre lasers, Nd:YAG lasers and disk lasers all belong to the same group.
In a fibre laser, a set of laser diodes produces the laser beam. The beam is transmitted via an optic fibre which amplifies it. The augmented beam exits the optic fibre, which is focussed by a lens after collimation on the material that requires cutting.
Advantages of Sources of Fibre Laser
- There are no moving parts i.e. fans for circulating gas, in the case of the source of the fibre laser when compared to a traditional CO2 It also does not have any mirrors as in the source that generates light. This helps to reduce the operating costs and maintenance requirements.
- Fibre lasers have greater energy efficiency when compared to CO2 lasers having similar power.
- When compared to a CO2 laser, the cutting speed of the fibre laser of thin sheets is much faster. This is because the sheets absorb the wavelength of the fibre laser better.
- Reflective materials such as aluminium, copper and brass can be cut effortlessly, without any problems using fibre laser as it does not cause back reflections that damage the machine.
Direct Diode Lasers
This is a recent entry in the solid-state laser field. Here, many laser beams are emitted from diodes of various wavelengths that are overlaid using techniques of beam combining. Diode lasers don’t have a brightness-enhancement stage like fibre lasers and this allows for greater wall-plug efficiency and lower optical loss. This diode laser also produces beam quality that is lower compared to that of fibre lasers. Diode lasers are used commonly for sheet metal cutting processes.
In the last few years, improvements in the precision of cutting, superior edge squareness, heat control and accuracy have ensured that laser cutting has also found its place among other techniques of cutting such as oxy-fuel and plasma cutting; and today, laser cutting is a very popular method of cutting that is being employed widely in many applications and industries.