Laser cutting machine is widely used in industrial manufacturing industry. Laser cutting machine is used for metal and nonmetal cutting, and uses laser beam to melt the surface of materials. This paper will introduce the principle of laser cutting machine.

Principle of laser cutting machine - introduction

The laser cutting machine technology uses the energy released when the laser beam hits the sheet metal surface. The sheet metal melts and is blown away by gas. As the laser power is very concentrated, only a small amount of heat is transferred to the rest of the plate, almost without deformation. The laser can be used for high-precision cutting of complex shaped blanks without further processing.

Carbon dioxide laser beam is generally used as the laser source, and the working power is 500-5000W. This power level is lower than the power required by many household electric heaters, and the laser beam is concentrated in a very small area due to lenses and mirrors. High energy concentration allows rapid local heating to melt the metal sheet.

Stainless steel less than 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 form on the cut surface. The maximum thickness of cutting can be increased to 16mm, but the size error of cutting parts is large.

Since its launch, as a high-tech laser technology, it has developed laser products suitable for various industries according to different social needs, such as laser printers, laser beauty machines, laser marking, CNC laser cutting machines, laser cutting machines and other products. Since the laser industry started relatively late in China, it lags behind some developed countries in technology research and development to a large extent, At present, domestic manufacturers of laser products mainly produce laser products, including some key components such as laser tubes, driving motors, vibration mirrors, focusing lenses, etc. This has led to rising costs and increased the burden on consumers.

In recent years, with the progress of domestic laser technology, the complete machine and some spare parts have gradually approached the advanced foreign products. In some aspects, it is even better than foreign products. In addition to technical advantages, the domestic market still dominates. However, in terms of stability and patience in some precision processing and equipment, foreign advanced products still have absolute advantages.

In the laser cutting machine, its main work is the laser tube, so we need to understand the laser tube.

Clearly understand the importance of laser equipment and laser tube. The following is a common laser tube to judge. CO2 laser tube!

The laser tube is made of hard glass, so it is a fragile and fragile material. To understand the CO2 laser tube, you must first understand the structure of the laser tube. For example, the CO2 laser is a layer of casing structure, most of which is a layer of discharge tube. However, the diameter of the CO2 laser discharge tube is even thicker than the laser tube itself. The thickness of the discharge tube is proportional to the diffraction reaction caused by the size of the spot, and the length of the discharge tube is proportional to the output power of the discharge tube.

During the operation of the laser cutting machine, the laser tube will generate a lot of heat, which will affect the normal operation of the cutting machine. Therefore, a cooler in a special area is needed to cool the laser tube to ensure the normal operation of the laser cutting machine at a constant temperature. Cw-6200 is selected for 200W laser, and the cooling capacity is 5.5kw; 650W laser shall be cw-7800, and the cooling capacity can reach 23KW.

Principle of laser cutting machine - cutting characteristics

Advantages of laser cutting:

Advantage I High efficiency

Due to the transmission characteristics of laser, laser cutting machines are generally equipped with multiple CNC workstations, and the entire cutting process can be fully CNC. During operation, it is only necessary to change the NC program to apply to the cutting of parts with different shapes. It can not only conduct two-dimensional cutting, but also realize three-dimensional cutting.

Advantage II - Fast

Power 1200W laser cutting 2mm thick low-carbon steel plate, cutting speed can reach 600cm/min; The cutting speed of 5mm thick polypropylene resin board can reach 1200cm/min. It is not necessary to clamp and fix materials during laser cutting.

Advantages Ⅲ - Good cutting quality

Answer: The laser cutting incision is narrow, the two sides of the gap are parallel and perpendicular to the surface, and the size accuracy of the cutting part can reach ± 0.05mm.

2： The cutting surface is clean and beautiful, and the surface roughness is only tens of microns. Laser cutting can even be used as the final process. Parts can be directly used without machining.

3： After laser cutting, the width of the heat affected zone is very small, the performance of the material near the cutting seam is almost unaffected, the workpiece deformation is small, the cutting accuracy is high, the geometric shape of the cutting seam is good, and the cross section shape of the seam is regular rectangle. Table 1 shows the comparison of laser cutting, oxyacetylene cutting and plasma cutting methods. The cutting material is low carbon steel plate with a thickness of 6.2mm.

Advantage IV - non-contact cutting

In the process of laser cutting, there is no direct contact between the cutting torch and the workpiece, and there is no tool wear. To process parts with different shapes, it is not necessary to change the "tool", just change the output parameters of the laser. The laser cutting process has low noise, small vibration and little pollution.

Advantage V - cutting materials available

Compared with oxyacetylene cutting and plasma cutting, there are many kinds of laser cutting materials, including metal, non-metal, metal and non-metallic matrix composites, leather, wood and fiber.

Principle of laser cutting machine - cutting mode

I Vaporization cutting

The removal of processing materials is mainly through evaporation of materials.

In the process of vaporization cutting, under the action of the focused laser beam, the temperature of the worktable rapidly rises to the vaporization temperature, the material vaporizes in large quantities, and the high-pressure steam formed is ejected out at supersonic speed. At the same time, a "hole" is formed in the laser action area, and the laser beam is reflected many times in the hole, which makes the absorption of the laser to the material increase rapidly.

In the process of high-speed high-pressure steam injection, the melt in the gap is blown out from the gap at the same time until the workpiece is cut off. The internal vaporization cutting mainly depends on the way to vaporize the material, so the required power density is very high, which should generally reach more than 10 watts per square centimeter.

Laser usually uses vapor cutting to cut materials with low ignition point, such as wood, carbon and some plastics, as well as refractory materials, such as ceramics. When using pulsed laser to cut materials, vaporization cutting method is usually used.

Melt cutting II reaction

In fusion cutting. If the auxiliary air flow not only blows the molten material into the cutting seam, but also changes the thermal reaction with the workpiece, another heat source is added during the cutting process, which is called reactive melt cutting. Usually, the gas reacting with the workpiece is oxygen or a mixture containing oxygen.

When the surface temperature of the workpiece reaches the ignition point temperature, strong combustion exothermic reaction will occur, which can greatly improve the ability of laser cutting. For low carbon and stainless steel, the exothermic combustion reaction provides 60% of the energy. For active metals such as titanium, combustion can provide about 90% of the energy.

Therefore, reactive melt cutting and laser vaporization cutting, general melt cutting, require a lower laser power density, which is only 1/20 of vaporization cutting and 1/2 of melting cutting. However, in reactive melt cutting, the internal combustion reaction will cause some chemical changes on the material surface, thus affecting the performance of the workpiece.

Ⅲ Melt cutting

In the laser cutting process, if the coaxial auxiliary blow molding system with laser beam is added, the removal of melt in the cutting process depends not only on the vaporization of the material itself, but also mainly on the role of high-speed auxiliary devices. Under the action of air flow, the melt is constantly blown away from the cutting joint. This cutting process is called melt cutting.

In the process of melting and cutting, 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 cutting is only 1/10 of that for evaporation cutting.

Ⅳ Laser scribing

The 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 weaken the adhesion of semiconductor materials. The quality of laser slice is measured by the size of surface fragments and heat affected zone.

Ⅴ Cold cutting

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 energy similar to that of many organic materials, and such high-energy photons are used to strike and break the bonds of organic materials. So as to achieve the purpose of cutting. This new technology has broad application prospects, especially in the electronic industry will be very widely used.

Thermal stress VI cutting

Under laser beam heating, the surface of brittle materials is prone to produce large

emphasize. Therefore, they can be ruptured rapidly and orderly by laser heated stress points. This cutting process is called laser thermal stress cutting. The mechanism of thermal stress cutting is as follows: laser beam heats a certain area of brittle materials to produce obvious temperature gradient.

When the surface temperature of the workpiece is high, expansion occurs. When the temperature of the inner layer of the workpiece is low, it can prevent expansion, thus producing tensile stress on the surface of the workpiece. When these two stresses exceed the ultimate breaking strength of the workpiece itself. Cracks can occur in the workpiece. It causes the workpiece to break along the crack. The rate of thermal stress cutting is about m/s. This cutting method is suitable for cutting glass, ceramics and other materials.