Laser cutting info
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Main processing technology of laser cutting
Release Time：2022/05/25 Blog Browsing Times：44
There are four main processing technologies of laser cutting machine : vaporization cutting, melting cutting, flame cutting and controlled fracture cutting.
1. Vaporization cutting In the process of laser gasification cutting, the speed of the material surface temperature rising to the boiling point temperature is so fast that it is enough to avoid melting caused by heat conduction. Therefore, some materials vaporize into steam and disappear, and some materials are blown away from the bottom of the cutting seam as ejecta by the auxiliary gas flow. In this case, very high laser power is required.
In order to prevent the material vapor from condensing on the slit wall, the thickness of the material must not greatly exceed the diameter of the laser beam. This process is therefore only suitable for applications where the exclusion of molten material must be avoided. In fact, this processing is only used in very small application fields of iron-based alloys.
This process cannot be used for, wood and some ceramics. Materials that are not in a molten state and are therefore unlikely to allow the material vapor to re condense. In addition, these materials usually need to achieve thicker cuts. In laser gasification cutting, the optimal beam focusing depends on the material thickness and beam quality. Laser power and gasification heat have only a certain influence on the optimal focus position. When the thickness of the plate is constant, the maximum cutting speed is inversely proportional to the gasification temperature of the material. The required laser power density is greater than 108W / cm2 and depends on the material, cutting depth and beam focus position. When the plate thickness is certain, assuming sufficient laser power, the maximum cutting speed is limited by the gas jet speed.
2. Melt cutting In laser melting cutting, after the workpiece is locally melted, the molten material is sprayed out with the help of air flow. Because the transfer of material only occurs in its liquid state, this process is called laser melting cutting. The laser beam and high-purity inert cutting gas promote the molten material to leave the slit, and the gas itself does not participate in the cutting. Laser melting cutting can obtain higher cutting speed than gasification cutting. The energy required for gasification is usually higher than that 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. When the laser power is constant, the limiting factor is the air pressure at the slit and the thermal conductivity of the material. For ferrous materials and titanium metals, laser melting cutting can obtain oxidation-free notch. The laser power density that produces melting but not gasification is between 104w / cm2 and 105 w / cm2 for steel materials.
3. Oxidation melting cutting (laser flame cutting) Melting cutting generally uses inert gas. If oxygen or other active gas is replaced, the material will be ignited under the irradiation of laser beam, and another heat source will be generated by fierce chemical reaction with oxygen to further heat the material, which is called oxidation melting cutting. Due to this effect, for structural steel with the same thickness, the cutting rate obtained by this method is higher than that by melting cutting. On the other hand, this method may have worse notch quality than melting cutting. In fact, it will produce wider slits, obvious roughness, increased heat affected zone and worse edge quality. Laser flame cutting is not good when machining precision models and sharp corners (there is a risk of burning sharp corners). A pulsed laser can be used to limit the thermal effect, and the power of the laser determines the cutting speed. When the laser power is constant, the limiting factor is the supply of oxygen and the thermal conductivity of the material.
4. Controlled fracture cutting For brittle materials that are easy to be damaged by heat, high-speed and controllable cutting through 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, causing the earth thermal gradient and serious mechanical deformation in this area, resulting in the formation of cracks in the material. As long as a uniform heating gradient is maintained, the laser beam can guide the crack in any desired direction. This method is commonly used in food packaging processing. A large part of the food we usually contact is processed by laser-controlled fracture and cutting.