Lasers have applications in teaching, military, and industry. Laser cutting machine is one of its applications. Laser cutting machines are used for cutting metal and non-metal. The laser beam melts the surface of the material. This article will describe the principle of laser cutting machine.
The principle of laser cutting machine-introduction
Laser cutting machine technology uses the energy released when the laser beam is irradiated to the surface of the metal plate. The metal sheet is melted and the molten slag is blown away by the gas. Because the laser power is very concentrated, only a small amount of heat is transferred to other parts of the metal plate, causing little or no deformation. The laser can be used to cut blanks of complex shapes very accurately, and the cut blanks do not need to be further processed.
Laser source generally uses carbon dioxide laser beam, working power is 500 ~ 5000 watts. This level of power is lower than the power required by many domestic electric heaters, because the laser beam is concentrated in a small area due to the lens and mirror. The high concentration of energy enables rapid local heating to melt the metal sheet.
Using laser cutting equipment can cut stainless steel below 16mm. Adding oxygen to the laser beam can cut 8-10mm thick stainless steel. However, after oxygen cutting, a thin oxide film will be formed on the cutting surface. The maximum thickness of the cutting can be increased to 16mm, but the size error of the cutting part is large.
As a high-tech laser technology, since its inception, it has been developing laser products suitable for various industries, such as laser printers, laser beauty machines, laser marking CNC laser cutting machines, laser cutting machines, etc., for different social needs. Since the domestic laser industry started late, it lags behind some developed countries to a great extent in technological research and development. At present, laser products produced by domestic laser product manufacturers, some key parts such as laser tubes, drive motors, galvanometers, and focus Mirror and other products are still used. This has caused a rise in costs and increased consumer commitment.
In recent years, with the advancement of domestic laser technology, the R&D and production of complete machines and some spare parts have gradually moved closer to foreign advanced products. In some respects, it is even better than foreign products, coupled with the advantages of Jiege, it still occupies a dominant position in the domestic market. But in some precision processing and equipment, stability and resistance, foreign advanced products still occupy an absolute advantage.
Laser cutting machine principle-principle
In the laser cutting machine, the main work is the laser tube, so we have to understand the laser tube.
clearly knows the importance of laser tubes in laser equipment. The following is the most common laser tube to judge. CO2 laser tube!
The composition of the laser tube is made of a hard glass, so it is a fragile and fragile substance. To understand the CO2 laser tube, we must first understand the structure of the laser tube, like this carbon dioxide laser uses a layered sleeve structure, the most inside is a layer of discharge tube. However, the diameter of the carbon dioxide laser discharge tube is larger than that of the laser tube itself. The thickness of the discharge tube is proportional to the diffraction reaction caused by the size of the spot. The length of the tube and the output power of the discharge tube also form a Species ratio.
During the operation of the laser cutting machine, the laser tube will generate a lot of heat, which affects the normal operation of the cutting machine. Therefore, a special water chiller is required to cool the laser tube to ensure that the laser cutting machine works normally at a constant temperature. It is sufficient to use CW-6200 for the 200W laser with a cooling capacity of 5.5KW; CW-7800 for the 650W laser with a cooling capacity of 23KW.
The principle of laser cutting machine-cutting characteristics
Advantages of laser cutting:
Advantage Ⅰ——High efficiency
Because of the transmission characteristics of the laser, the laser cutting machine is generally equipped with multiple CNC working tables, and the entire cutting process can be fully CNC controlled. During operation, only need to change the CNC program, it can be applied to the cutting of parts of different shapes, both two-dimensional cutting and three-dimensional cutting.
Advantage Ⅱ——fast speed
Fiber cutting machine 2mm thick low-carbon steel plate with a power of 1200W, the cutting speed can reach 600cm/min; cutting 5mm thick polypropylene resin board, the cutting speed can reach 1200cm/min. Materials need not be clamped and fixed during laser cutting.
Advantage Ⅲ——Good cutting quality
One: Laser cutting incision is narrow and narrow, both sides of the slit are parallel and perpendicular to the surface, and the dimensional accuracy of the cut parts can reach ±0.05mm.
2: The cutting surface is smooth and beautiful, and the surface roughness is only a few tens of microns. Even laser cutting can be used as the last process without mechanical processing, and the parts can be used directly.
Three: After the material is laser cut, the width of the heat affected zone is very small, the performance of the material near the slit is almost not affected, and the workpiece deformation is small, the cutting accuracy is high, the geometry of the slit is good, and the shape of the slit cross section is more Regular rectangle. The comparison of laser cutting, oxyacetylene cutting and plasma cutting methods is shown in Table 1. The cutting material is 6.2mm thick low carbon steel plate.
Advantage Ⅳ——Cutting non-contact
During laser cutting, there is no direct contact between the torch and the workpiece, and there is no tool wear. For processing parts of different shapes, there is no need to change the "tool", only the output parameters of the laser need to be changed. The laser cutting process has low noise, small vibration and little pollution.
Advantages Ⅴ-there are many materials that can be cut
Compared with oxyacetylene cutting and plasma cutting, there are many types of laser cutting materials, including metal, non-metal, metal-based and non-metal-based composite materials, leather, wood and fiber.
Laser cutting machine principle-cutting method
Ⅰ Vaporized cutting
refers to the removal of the processed material mainly by vaporizing the material.
In the process of vaporization cutting, the temperature of the workpiece rises rapidly to the vaporization temperature under the action of the focused laser beam, the material is vaporized in large quantities, and the high-pressure steam formed is sprayed outward at supersonic speed. At the same time, a "hole" is formed in the laser action area. The laser beam is reflected multiple times in the hole and the material's absorption of laser light is rapidly increased.
In the process of high-pressure steam high-speed injection, the molten material in the slit is simultaneously blown away from the slit until the workpiece is cut. Intrinsic vaporization cutting is mainly carried out by vaporizing the material, so the required power density is very high, generally it should be more than 10 8th watts per square centimeter.
Vaporized cutting is a method of laser cutting some low-burning point materials (such as wood, carbon and certain plastics) and refractory materials (such as ceramics, etc.). Vaporized cutting methods are often used when cutting materials with pulse lasers.
ⅡReactive melting cutting
In melting cutting. If the auxiliary air flow not only blows away the molten material in the cutting slit, but also can change the heat reaction with the workpiece, so that the cutting process adds another heat source, such cutting is called reactive melting cutting. Usually the gas that can react with the workpiece is oxygen or a mixed gas containing oxygen.
When the surface temperature of the workpiece reaches the ignition temperature, a strong combustion exothermic reaction will occur, which can greatly improve the ability of laser cutting. For mild steel and stainless steel, the energy provided by the combustion exothermic reaction is 60%. For active metals such as titanium, the energy provided by combustion is about 90%.
Therefore, compared with laser vaporization cutting and general melting cutting, reactive melt cutting requires a lower laser power density, which is only 1/20 of vaporization cutting and 1/2 of melt cutting. However, in reactive melting cutting, the internal combustion reaction will cause some chemical changes on the surface of the material, which will affect the performance of the workpiece.
Ⅲ Melt cutting
In the fiber laser machine cutting process, if an auxiliary blowing system coaxial with the laser beam is added, the removal of the melt during the cutting process is not solely based on the material vaporization itself, but mainly depends on the blowing action of the high-speed auxiliary air flow to remove the melt Continuously blowing away from the slit, this cutting process is called melt cutting.
In the process of melting and cutting, the temperature of the workpiece no longer needs to be heated above the vaporization temperature, so the required laser power density can be greatly reduced. According to the latent heat ratio of material melting to vaporization, the laser power required for melting and cutting is only 1/10 of the vaporizing and cutting method.
Ⅳ laser scribing
This method is mainly used for: semiconductor materials; using a laser beam with a high power density to draw a shallow groove on the surface of the semiconductor material workpiece, because this groove weakens the bonding force of the semiconductor material. Accessible machinery Method or vibration method to break it. The quality of laser scribing is measured by the surface debris and the size of the heat-affected zone.
Ⅴ Cold cutting
This is a new processing method, which was proposed with the emergence of high-power excimer lasers in the ultraviolet band in recent years. Its basic principle: The energy of ultraviolet photons is similar to the binding energy of many organic materials. Use such high-energy photons to hit the bonding 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.
Ⅵ Thermal stress cutting
Brittle material is heated by laser beam. Its surface is prone to generate large stress. It can be neat and quick to cause fracture by laser heating stress point. Such cutting process is called laser thermal stress cutting. The mechanism of thermal stress cutting is: the laser beam heats a certain area of the brittle material, causing it to produce a significant temperature gradient.
The surface temperature of the workpiece is high to expand. The temperature of the inner layer of the workpiece is low to hinder the expansion, resulting in tensile stress on the surface of the workpiece. The inner layer produces radial compression stress. When these two kinds of stress exceed the fracture ultimate strength of the workpiece itself. There will be cracks on the workpiece. The workpiece is broken along the crack. The speed of thermal stress cutting-strands are on the order of m/s. This cutting method for fiber laser cutting is suitable for cutting glass, ceramics and other materials.
Summary: Laser cutting machine is a cutting technology that uses laser characteristics and lens focusing to concentrate energy to melt or vaporize the surface of the material. It can achieve the advantages of good cutting quality, fast speed, many cutting materials and high efficiency.
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