Laser cutting is almost the most advanced cutting process in the world. It can cut most metal and non-metallic materials and can be used in many industries. It has the advantages of precision manufacturing, flexible cutting, special-shaped processing, one-time forming, high speed, high efficiency, and can solve many problems that cannot be solved by conventional methods. This article will talk about this machine with you.
Laser cutting is a process in which the laser beam emitted by the laser generator is focused by the lens to form a tiny high-energy spot at the focus, so that the spot can be focused at a suitable position of the material, absorbed by the material, rapidly vaporized, melted, ablated or reached the ignition point, and the molten waste is blown away with high-pressure auxiliary gases (including carbon dioxide, oxygen, nitrogen, etc.). The laser head is driven by a programmable servo motor, and the cutting head moves along a predetermined route with the beam moving on the material, so as to cut work-pieces of various shapes.
Light is red, orange, yellow and green, which can be absorbed or reflected by objects; Laser is also light, which will show different characteristics according to different wavelengths. The gain medium of the laser generator (that is, the medium that can convert electric energy into laser) determines the laser wavelength, output power and application field. The gain medium of laser can be divided into gas, liquid and solid. The representative gas is CO2 gas laser; The representative solids include fiber laser, YAG laser, ruby laser, semiconductor laser, etc; Liquid lasers use some liquids (usually organic solvents, such as dyes) as the working medium to generate lasers, and emit lasers.
Different cutting object materials can absorb different laser wavelengths, so appropriate laser generators need to be adapted. At present, fiber laser generator is the most widely used in automobile industry.
Laser cutting methods mainly include melting cutting, oxidation cutting, vaporization cutting, guided fracture cutting, etc. When selecting cutting methods, their characteristics, plate materials and sometimes cutting shapes should be considered. Laser vaporization cutting requires more heat than melting, and is suitable for cutting extremely thin metal materials and non-metallic materials. Laser oxidation cutting is faster with the help of the reaction heat of oxygen and metal, and the cutting quality is relatively poor, which is suitable for thick plate cutting. Laser melting cutting is widely used in automobile and sheet metal industry due to the use of shielding gas to prevent slag splashing, smooth cutting seam and good cutting quality. In addition, melting cutting and gasification cutting can obtain oxidation free cutting seam, which is of great significance for cutting with special requirements.
The technological process of laser cutting is relatively simple. The laser cutting path and parameter program are set in advance according to different products. Generally, holes are cut first, then edges are cut. The cutting production can be directly carried out after the first piece has passed the commissioning. But it is not easy to cut the best quality products. It is closely related to cutting materials, laser mode, power, cutting speed, auxiliary gas pressure, etc.
The laser generally has three working modes: continuous mode, modulation mode and pulse mode.
In the continuous mode, the output power of the laser is constant, which makes the heat entering the sheet more uniform. It is suitable for fast cutting in general. On the one hand, it can improve the work efficiency, on the other hand, it is also necessary to avoid the malignant change of the heat affected zone caused by heat concentration.
The laser power of the modulation mode is a function of the cutting speed. It can keep the heat entering the sheet metal at a relatively low level by limiting the power at each point, so as to prevent the burn at the edge of the cutting seam. Because of its complex control, it is not very efficient and can only be used in a short period of time.
Although the pulse mode can be subdivided into three cases, it is actually just the difference in strength, and is often selected according to the characteristics of materials and the accuracy of structures.
The laser often operates in the continuous output mode. In order to obtain the best cutting quality, it is necessary to adjust the feed rate for a given material, such as acceleration, deceleration and delay when turning. Therefore, in the continuous output mode, reducing the power is not enough, and the laser power must be adjusted by changing the pulse.
The gas used for laser cutting equipment includes laser working gas, shielding gas and auxiliary gas.
Nitrogen is generally used for cutting stainless steel and some high-strength steel, which is used to prevent oxidation reaction and blow off molten materials. The purity of nitrogen is required to be high. For stainless steel with a diameter of more than 8mm, the purity of 99.999% is generally required. Oxygen is suitable for thick plate cutting, high-speed cutting and extremely thin plate cutting. Air is suitable for cutting aluminum, non-metallic and galvanized steel plates. To a certain extent, it can reduce oxide film and save costs. In terms of cost, the oxygen used for carbon steel cutting is relatively cheap, and the nitrogen used for carbon steel cutting is large. The thicker the stainless steel is, the higher the nitrogen content and purity are, the higher the cost is. At present, the cutting cost of high-purity nitrogen is about 35-40CNY/h, which is higher than that of oxygen, about 10-15CNY/h.
The maximum speed of laser cutting can reach 40m/min, and the actual processing is usually only 1/3 - 1/2 of the maximum speed. Because the higher the speed, the lower the dynamic accuracy of the servo mechanism, which directly affects the cutting quality. When cutting round holes, the higher the cutting speed, the smaller the hole diameter, and the worse the roundness. The maximum cutting speed can only be used to improve efficiency in long straight cutting. In the actual cutting process, it is necessary to adjust the laser power, air pressure and other relevant parameters to achieve the optimal cutting speed suitable for the product according to the material, thickness and relevant technical requirements of the product.
According to different product requirements, it is necessary to continuously adjust the parameters under different working conditions to achieve the best process parameters. The nominal positioning accuracy that can be achieved by laser cutting is 0.08mm, and the repeated positioning accuracy is 0.03mm. In fact, the minimum tolerance that can be achieved is: aperture ± 0.05mm, hole location ± 0.2mm.
Different materials and different thicknesses require different melting energy, and the required laser output power is also different. During production, it is necessary to balance the production speed and quality, select and set appropriate output power and cutting speed, ensure that there is appropriate energy in the cutting area, and materials can be effectively melted and blown away in time.
The efficiency of the laser to convert electrical energy into laser energy is about 30%~35%, the output power is 1500W, and the input power is about 4285W~5000W. The real input power consumption is far greater than the nominal output power. In addition, according to the principle of energy conservation, other energies are converted into heat energy for emission, so the laser needs to be equipped with a chiller to cool down.
Technology and Cost of Laser Cutting Machine
Moderator: baker