Various Cutting Methods Of Laser Cutting Machine
Laser cutting is a non-contact processing method with high energy and good density controllability. The laser spot with high energy density is formed after focusing the laser beam, which has many characteristics when used in cutting. There are four different ways of laser cutting in order to deal with different situations.
In laser melting cutting, the melted material is ejected by means of airflow after the workpiece is melted locally. Because the transfer of material only occurs in its liquid state, this process is called laser melting cutting.
The laser beam with high purity inert cutting gas makes the melted material leave the slit, while the gas itself is not involved in cutting. Laser melting cutting can get higher cutting speed than gasification cutting. The energy required for gasification is usually higher than the energy required to melt the material. In laser melting cutting, the laser beam is only partially absorbed. The maximum cutting speed increases with the increase of laser power, and decreases almost inversely with the increase of plate thickness and material melting temperature. In the case of a certain laser power, the limiting factor is the air pressure at the slit and the thermal conductivity of the material. For iron and titanium materials, laser melt cutting can obtain non oxidation notches. For steel materials, the laser power density is between 104w / cm2 and 105W / cm2.
In the process of laser gasification cutting, the speed of material surface temperature rising to boiling point temperature is so fast that it can avoid the melting caused by heat conduction, so some materials vaporize into steam and disappear, and some materials are blown away from the bottom of cutting seam by auxiliary gas flow as ejecta. Very high laser power is required in this case.
In order to prevent the material vapor from condensing on the slit wall, the thickness of the material must not be much larger than the diameter of the laser beam. This process is therefore only suitable for applications where the elimination of melted materials must be avoided. In fact, the process is only used in a very small field of use of iron-based alloys.
The process cannot be used for materials such as wood and some ceramics, which are not in a molten state and are unlikely to allow the material vapor to recombine. In addition, these materials usually have to achieve a thicker cut. In laser gasification cutting, the optimal beam focusing depends on the material thickness and beam quality. Laser power and heat of vaporization have only a certain effect on the optimal focal position. The maximum cutting speed is inversely proportional to the gasification temperature of the material when the thickness of the plate is fixed. The required laser power density is greater than 108W / cm2 and depends on the material, cutting depth and beam focus position. In the case of a certain thickness of the plate, assuming that there is enough laser power, the maximum cutting speed is limited by the gas jet speed.
3.Controlled fracture cutting
For brittle materials that are easy to be damaged by heat, high-speed and controllable cutting by laser beam heating is called controlled fracture cutting. The main content of this cutting process is: the laser beam heats a small area of brittle material, which causes a large thermal gradient and serious mechanical deformation in this area, leading to the formation of cracks in the material. As long as the uniform heating gradient is maintained, the laser beam can guide the generation of cracks in any desired direction.
4.Oxidation melting cutting (laser flame cutting)
Generally, inert gas is used for melting and cutting. If oxygen or other active gas is used instead, the material will be ignited under the irradiation of laser beam, and another heat source will be generated due to the intense chemical reaction with oxygen to further heat the material, which is called oxidation melting and cutting.
Because of this effect, the cutting rate of structural steel with the same thickness can be higher than that of melting cutting. On the other hand, the quality of the incision may be worse than that of the melt cutting. In fact, it will produce wider slits, obvious roughness, increased heat affected zone and worse edge quality. Laser flame cutting is not good at machining precision models and sharp corners (there is a danger of burning the sharp corners). Pulse mode lasers can be used to limit thermal effects, and the power of the laser determines the cutting speed. In the case of a certain laser power, the limiting factor is the supply of oxygen and the thermal conductivity of the material.
Post time: Dec-21-2020