Laser cutting machines are widely used equipment in today's industrial manufacturing industry. Laser cutting machines are used for metal and non-metal cutting, using a laser beam to melt the surface of the material. This article will introduce the principle of laser cutting machine.
Laser cutter technology uses the energy released when a laser beam hits a sheet metal surface. The sheet metal melts and is blown away by the gas. Because the laser power is very concentrated, only a small amount of heat is transferred to the rest of the board, which is hardly deformed. This laser can be used to cut complex shapes with high accuracy without further processing.
The laser source generally uses a carbon dioxide laser beam, and the working power is 500 ~ 5000 watts. This power level is lower than that required for many domestic electric heaters, and because of the lenses and mirrors, the laser beam is condensed in a small area. The high energy concentration allows rapid local heating to melt metal plates.
Stainless steel below 16mm can be cut with laser cutting equipment. It is possible to cut 8 ~ 10mm thick stainless steel by adding oxygen to the laser beam, but after oxygen cutting, a thin oxide film will be formed on the cutting surface. The maximum thickness of the cut can be increased to 16mm, but the size error of the cut part is very large.
Since its introduction, as a high-tech laser technology, it has developed laser products suitable for various industries according to the different needs of the society, such as laser printers, laser beauty machines, laser marking, CNC laser cutting machines, laser cutting machines and other products. As the laser industry started relatively late in China, it largely lags behind some developed countries in technological research and development. At present, domestic manufacturers of laser products mainly produce laser products. Some of the key components such as laser tubes, drive motors, and vibration mirrors , Focus lens and so on until the product is used. This has led to higher costs and increased consumer burdens.
In recent years, with the advancement of domestic laser technology, the whole machine and some spare parts have gradually approached advanced foreign products. In some aspects, it is even better than foreign products. Coupled with technological advantages, the domestic market still dominates. But in some precision processing and equipment, stability and patience, foreign advanced products still have absolute advantages.
In the laser cutting machine, the main work is the laser tube, so we need to understand the laser tube.
Clearly understand the importance of laser equipment and laser tubes. The following is to use one of the most common laser tubes to judge. CO2 laser tube!
The laser tube is made of hard glass, so it is a brittle and brittle material. To understand the CO2 laser tube, you must first understand the structure of the laser tube. For example, a carbon dioxide laser is a layered tube structure, and most of it is a layer of discharge tube. However, the diameter of the carbon dioxide laser discharge tube is even thicker than the laser tube itself. The thickness of the discharge tube is proportional to the diffraction response caused by the spot size, and the length of the discharge tube is also proportional to the output power of the discharge tube.
During the operation of the laser cutting machine, the laser tube generates a lot of heat, which affects the normal operation of the cutting machine. Therefore, a special area cooler is required to cool the laser tube to ensure the normal operation of the laser cutting machine at a constant temperature. Choose 200w laser for cw-6200, cooling capacity is 5.5kw; 650W laser should be cw-7800, cooling capacity can reach 23KW.
Laser cutting machine principle-cutting characteristics
Due to the transmission characteristics of lasers, laser cutting machines are generally equipped with multiple CNC workstations, and the entire cutting process can be fully CNC. In operation, only need to change the NC program, it can be applied to the cutting of parts of different shapes, not only can perform two-dimensional cutting, but also can achieve three-dimensional cutting.
Power 1200W laser cutting 2mm thick low carbon steel plate, cutting speed can reach 600cm / min; cutting 5mm thick polypropylene resin plate, cutting speed can reach 1200cm / min. There is no need to clamp and secure the material during the laser cutting process.
Advantage Ⅲ-Good cutting quality
Answer: The laser cutting incision is narrow. The two sides of the slit are parallel and perpendicular to the surface. The dimensional accuracy of the cutting part can reach ± 0.05mm.
Two: The cutting surface is clean and beautiful, and the surface roughness is only tens of microns. Even laser cutting can be used as the final process. Parts can be used directly without machining.
3: After laser cutting, the width of the heat-affected zone is small, the performance of the material near the cutting seam is hardly affected, the workpiece deformation is small, the cutting accuracy is high, the cutting seam geometry is good, and the cross-sectional shape of the seam is a regular rectangle . Table 1 shows a comparison of laser cutting, oxyacetylene cutting and plasma cutting methods. The cutting material is a low-carbon steel sheet having a thickness of 6.2 mm.
Advantage IV-Non-contact cutting
During the laser cutting process, there is no direct contact between the torch and the workpiece, and there is no tool wear. Machining parts of different shapes does not need to change the "tool", only the output parameters of the laser can be changed. The laser cutting process has low noise, small vibration and little pollution.
Advantage Ⅴ-Can provide cutting materials
Compared with oxyacetylene cutting and plasma cutting, there are many types of laser cutting materials, including metal, non-metal, metal and non-metal matrix composites, leather, wood and fiber.
Ⅰ Vapor cutting
Removal of the processing material is mainly by evaporation of the material.
During the vaporization cutting process, the temperature of the workpiece table rapidly rises to the vaporization temperature under the action of the focused laser beam, and a large amount of material is vaporized, and the high-pressure steam formed is ejected outward at a supersonic speed. At the same time, "holes" are formed in the laser active area, and the laser beam is reflected multiple times in the holes, which makes the laser's absorption of the material increase rapidly.
During the high-speed and high-pressure steam injection, the melt in the gap is blown out of the gap at the same time until the workpiece is cut. The internal vaporization cutting mainly depends on the way the material is vaporized, so the required power density is very high, which should generally reach 10 powers above eight watts per square centimeter.
Lasers typically use vapor phase cutting to cut materials with low ignition points, such as wood, carbon, and certain plastics, as well as refractory materials, such as ceramics. When cutting a material with a pulsed laser, a vapor cutting method is commonly used.
Melt Cutting II Reaction
During slicing. If the auxiliary airflow not only blows the melt into the cutting gap, but also changes the thermal reaction with the workpiece, another heat source is added during the cutting process. This cutting is called reactive fusion cutting. The gas usually reacting with the workpiece is oxygen or a mixture containing oxygen.
When the surface temperature of the workpiece reaches the ignition point temperature, a strong exothermic combustion reaction will occur, which can greatly improve the ability of laser cutting. For low carbon and stainless steel, the combustion exothermic reaction provides 60% of the energy. For active metals such as titanium, combustion provides approximately 90% of the energy.
Therefore, reaction fusion cutting and laser vaporization cutting,-general fusion cutting, the required laser power density is relatively low, only 1/20 of vaporization cutting, and 1/2 of fusion cutting. However, in reactive melting cutting, the internal combustion reaction causes some chemical changes on the surface of the material, which affects the performance of the workpiece.
Ⅲ Melt cutting
In the laser cutting process, if a coaxial auxiliary blow molding system with a laser beam is added, the melt removal during the cutting process depends not only on the vaporization of the material itself, but also mainly on the role of the high-speed auxiliary device. Under the action of air flow, the melt is continuously blown away from the cutting seam. This cutting process is called melting cutting.
In the melt cutting process, it is no longer necessary to heat the workpiece above the vaporization temperature, so the required laser power density can be greatly reduced. According to the latent heat ratio of material melting and evaporation, the laser power required for melting and cutting is only 1/10 of the evaporation cutting method.
Ⅳ laser scribing
This method is mainly used for: semiconductor materials; high-power-density laser beams are used to cut shallow grooves on the surface of semiconductor components, which weakens the bonding force of semiconductor materials. The quality of the laser section is measured by the size of the surface debris and the heat-affected zone.
Ⅴ Cold cut
This is a new processing method, which has been proposed in recent years with the emergence of high-power excimer lasers in the ultraviolet band. Its basic principle is that ultraviolet photons have similar energy to many organic materials, and this high-energy photons are used to strike the bonds of organic materials and break them. So as to achieve the purpose of cutting. This new technology has broad application prospects, especially in the electronics industry, and will be widely used.
Thermal Stress VI Cutting
Under the laser beam heating, the surface of brittle materials tends to produce larger
Emphasize. As a result, they can break neatly and quickly by laser-stressed stress points. This cutting process is called laser thermal stress cutting. The mechanism of thermal stress cutting is as follows: The laser beam heats a certain area of brittle material to produce a significant temperature gradient.
When the surface temperature of the workpiece is high, swelling occurs. When the temperature of the inner layer of the workpiece is low, expansion is prevented, thereby generating tensile stress on the surface of the workpiece. When these two stresses exceed the ultimate breaking strength of the workpiece itself. Cracks can appear in the workpiece. Causes the workpiece to break along the crack. The speed of thermal stress cutting is about m / s. This cutting method is suitable for cutting glass, ceramics and other materials.