Laser cutting machines consist of 3 parts.
1- Resonator (Beam source) where the laser beam is produced,
2- Machine body and moving axes,
3- The optical system through which the beam is transmitted to the cutting head.
1.Resonator (Beam source)
LASER stands for "Light Amplification by the Stimulated Emission of Radiation". In the first place, it is defined as a powerful light beam with high amplitude in the form of monochrome, very flat, intense and same-phase parallel waves. Carbon dioxide laser is the most common type of laser used in metal cutting. The working principle of this laser is very similar to that of the He-Ne laser. Here, carbon dioxide molecules generate the laser beam, while nitrogen provides the reverse deposition of carbon dioxide. In other words, the role of helium atoms matches the role of carbon dioxide atoms and the role of neon atoms matches the role of nitrogen atoms. In this type of laser, energies of 10 kW can be provided continuously. However, even in very short shocks, energy can be generated with values many times higher than this value.
One of the greatest dangers of this type of laser is that it is invisible, since its beam is located in the infrared region of the electromagnetic spectrum, also called heat radiation. Most industrial lasers require the use of special gases to generate the laser beam. The quality and selection of the gas directly affects the reliability of the laser and the efficiency of the process. Laser gases are usually special gases with high purity. The laser gases are supplied to the machine in separate tubes or pre-mixed in certain proportions. The process parameters (gas flow rate, pressure purity, etc.) for this pre-mixing or supply of gases in separate tubes are determined by each laser machine manufacturer and supplied to the machine under those conditions. The gases that make up the carbon dioxide laser are carbon dioxide, nitrogen and helium. Some laser gases may contain 4 or 5 components (CO, H2 and Ne can be added to the medium in addition to CO2, N2 and Helium).
Laser cutting machines use 3 types of laser beam sources. According to the order of technology development:
1. Standard CO2 laser
2. Slab Laser
3. Fibre Laser
Standard CO2 lasers, which are the first type of these laser beam sources, require a continuous gas supply from outside. Gas consumption is higher than slab lasers and fibre lasers. The laser beam spreads more than slab and fibre lasers. In laser cutting machines with this type of resonator, if the beam path is long, additional focusing and rectifier elements are used to balance the beam scattering. These elements require additional cost, periodic maintenance-change and service cost.
In standard and slab laser cutting machines, the beam is transported to the cutting head with a mirror system. On the mirrors, some amount of the beam is converted into heat energy in each mirror. The heat generated is cooled by providing water flow through the water channels inside the mirrors.
The advantages of fibre lasers are that there is no gas consumption and the laser beam is transported to the cutting head by fibre optic cable without the need for mirrors. There is no power loss in fibre optic cables and therefore no additional cooling system is required. Their energy efficiency is much higher (e.g. on average, CO2 lasers consume 10kW of electrical energy for 1kW of laser energy, while fibre lasers consume 3-4kW of electrical energy). However, the high production costs of fibre lasers are currently a disadvantage. Another disadvantage is the decrease in cutting quality and speed as the material thickness increases. In addition, fibre lasers can reach energies of 40 kW and the standard wavelength of fibre lasers is 10 times lower than CO2 lasers.
2. Machine body and moving axes
In order to maintain uninterrupted continuous cutting quality, smoothness and precision, the machine body must not be affected by axis movements and external vibrations from the external environment.
3. Optical system
t is the path that the beam follows from the laser beam source until it leaves the cutting head. Depending on the type of resonator used, it consists of flat mirrors, focusing and straightening mirrors, beam path and lens. Almost all of them have a certain lifetime according to their maintenance and quality, which is a serious factor in cutting costs.
In fibre lasers, the optical system consists of fibre cable collimator lens and cutting head and there is no mirror cost.
Laser production provides both automation and reduces production errors. With the application of laser on various machines, production can be carried out 24 hours a day, and production costs are reduced by providing mass production. Especially with laser cutting processes, many moulds and apparatus are saved.
Cutting of steel, nickel alloys, titanium, chromium, stainless steel, aluminium and alloys etc. materials can be performed.
Some of the advantages of laser cutting are that it does not require cutting moulds and apparatus and the smoothness of the workpiece cutting surface. A high intensity laser beam is formed in the form of a small spot and heating occurs very little despite this intense energy.