There are two technical processes forlaser cutting machine steel: One is that pulsed lasers are suitable for metal materials. The second is that continuous laser is suitable for non-metallic materials, and the latter is an important application field of laser cutting technology.
Several key technologies of laser cutting machine steel are integrated technology of light, machine and electricity. In the laser cutting machine, the parameters of the laser beam, the performance and accuracy of the machine and the CNC system all directly affect the efficiency and quality of the laser cutting. Especially for parts with higher cutting accuracy or larger thickness, the following key technologies must be mastered and solved:
Focus position control technology.
One of the advantages of laser cutting is the high energy density of the beam, generally 10W/cm2. Since the energy density is inversely proportional to the area, the focal spot diameter is as small as possible to produce a narrow slit; at the same time, the focal spot diameter is also proportional to the focal depth of the lens. The smaller the focal depth of the focusing lens, the smaller the focal spot diameter. However, there are spatters in cutting, and the lens is too close to the workpiece to damage the lens. Therefore, the focal length of 5"~7.5" (127~190mm) is widely used in general high-power CO2 laser cutting machine industrial applications. The actual focal spot diameter is 0.1~0.4 mm. For high-quality cutting, the effective focal depth is also related to the lens diameter and the material to be cut. For example, cutting carbon steel with a 5" lens, the focal depth is within +2% of the focal length, that is, about 5mm. So control The position of the focus relative to the surface of the material to be cut is very important. Considering factors such as cutting quality, cutting speed, etc., in principle, 6mm metal materials, the focus is on the surface; 6mm carbon steel, the focus is on the surface; 6mm stainless steel, the focus Below the surface. The specific size is determined by experiment.
There are three easy ways to determine the focal position in industrial production:
(1) Printing method: The cutting head is moved from top to bottom, and laser beam printing is performed on the plastic plate, with the smallest printing diameter as the focus.
(2) Inclined plate method: Use a plastic plate placed obliquely at an angle to the vertical axis to pull it horizontally to find the smallest point of the laser beam as the focus.
(3) Blue spark method: remove the nozzle, blow air, hit the pulse laser on the stainless steel plate, and make the cutting head move from top to bottom until the largest blue spark is the focus.
For the cnc fiber metal laser cutting machine of the flying light path, due to the beam divergence angle, the length of the optical path is different between the near end and the far end, and the beam size before focusing is different. The larger the diameter of the incident beam, the smaller the diameter of the focal spot. In order to reduce the change of the focal spot size caused by the change of the beam size before focusing, the manufacturers of laser cutting systems at home and abroad provide some special devices for users to choose:
(1) Collimator. This is a commonly used method, that is, add a collimator to the output end of the CO2 laser for beam expansion. The beam diameter after beam expansion becomes larger and the divergence angle becomes smaller, so that the proximal and distal ends of the cutting work range The beam size before focusing is nearly the same.
(2) Add an independent lower axis of the moving lens to the cutting head. It and the Z axis that control the distance from the nozzle to the material surface (stand off) are two independent parts. When the machine tool table moves or the optical axis moves, the beam moves from the proximal end to the distal F axis at the same time, so that the beam spot diameter remains the same in the entire processing area after the beam is focused.
(3) Control the water pressure of the focusing lens (usually a metal reflective focusing system). If the beam size before focusing becomes smaller and the focal spot diameter becomes larger, the water pressure is automatically controlled to change the focus curvature to make the focal spot diameter smaller.
(4) Add x and y direction compensation optical path system on the flying optical path mechanical laser cutting machine
. That is, when the optical path at the distal end of the cutting is increased, the compensation optical path is shortened; on the contrary, when the optical path at the proximal end of the cutting is decreased, the compensation optical path is increased to keep the optical path length consistent.
Most organic and inorganic can be cut with laser cutting machine. In the metal processing industry, where industrial manufacturing has a heavy weight, many metal materials, no matter what hardness it has, can be cut without deformation. Common processes for laser cutting machines include vaporization cutting, melting cutting, oxidation melting cutting, and controlled fracture cutting.
1. Vaporized cutting
In the laser gasification cutting process, 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, so part of the material vaporizes into steam and disappears, and part of the material is sprayed from the bottom of the slit by auxiliary gas The flow blows away. In this case, very high laser power is required.
2. Melt cutting
In laser melting and cutting, the workpiece is partially melted and the melted material is ejected by airflow. Because the transfer of the material only occurs in its liquid state, the process is called laser melting and cutting.
3. Oxidation melting cutting (laser flame cutting)
Melting cutting generally uses inert gas. If it is replaced by oxygen or other active gases, the material is ignited under the irradiation of the laser beam, and a fierce chemical reaction occurs with oxygen to generate another heat source to further heat the material, which is called oxidative melting cutting .
4. Control fracture cutting
For brittle materials that are easily damaged by heat, high-speed and controllable cutting is performed by laser beam heating, which is called controlled fracture cutting. The main content of this cutting process is: the laser beam heats a small area of brittle material, causing a large thermal gradient and severe mechanical deformation in this area, causing the material to form cracks. As long as a uniform heating gradient is maintained, the laser beam can guide cracks in any desired direction.
When we use the CNC laser cutting machine, some dust is often generated which affects the eyes. For the sake of safety, we suggest that dust removal equipment must be installed, which is good for people's health and machines. It is recommended that you master the following three points, which can protect your body.
1) The laser is invisible, and the laser beam is invisible to the naked eye. If you open the hood for maintenance, you must pay attention. Don't accidentally touch the light path. It is more dangerous to touch the light path.
2) The harmful elements (znse) in the focusing lens of the laser cutting machine should not be in frequent contact with the lens, and the scrapped lens should be specially disposed of, and not littered.
3) Everyone pays attention to the material when processing, if it is carbon steel or stainless steel, there is no problem. If a large amount of aluminum alloy is processed, the cutting dust will be suspended in the air, which is harmful to the human body after inhalation. Also, when cutting aluminum plates, the light is very reflective, and the cutting head needs a protection device, otherwise it is easy to malfunction.
According to years of laser equipment research and development experience, laser cutting is much more environmentally friendly than plasma cutting and flame cutting. There is a lot of dust, dense smoke and strong light when the plasma cutting machine cuts, which requires a matching dust removal device. The laser cutting machine produces less dust when cutting, the light is not very strong, the noise is also very small, and it is more environmentally friendly.
The reason why the cutting parts of CNC laser cutting machine are deformed
First of all, we need to investigate whether it is caused by the improper dimming of the machine. The second analyzes what raw material is used for cutting. The reflective properties and metal characteristics of the raw materials may affect the cutting effect. If you are cutting thin metal plates, laser cutting is thermal cutting, and thermal cutting will definitely be deformed. Compared with flame cutting machine and plasma cutting machine, the deformation is relatively small. However, there is still deformation. The size of the deformation has a lot to do with the material being cut, the shape of the part, the cutting thickness, and the laser processing technology. The shape of the part largely determines the size of the deformation. For example, if you cut a square, the thermal deformation will not be too large. But if you cut a long and narrow rectangle (10*2000mm), the deformation will definitely be great. The reason for the deformation is due to uneven heating, which causes thermal expansion and contraction to cause the switch to change.
Why does the laser cutting machine cut a circle with corners? How to deal with it?
If the end point and the starting point cannot return to the same position, there may be a problem with the drawing or a problem with the machine structure. The treatment method can start from the following three aspects.
1. Turning acceleration and power should be adjusted well
2. The graphics are guaranteed to be round
3. Check the accuracy of your mechanical structure.
In summary, similar phenomena are also common. If the servo motor is difficult to control, it is recommended to ask a professional laser cutting machine manufacturer for technical guidance.
Maintenance and precautions of laser cutting machine in summer
Due to the rising temperature in summer and high air humidity, the scientific maintenance of the laser cutting machine can prevent many small problems in use, which are summarized as follows:
1. The idea that the temperature of the cooling water should not be too different from the air temperature. The laser and optical lenses of the laser cutting machine use water cooling methods. Because the water in the air will condense into water when it is cold, when the cooling water temperature is lower than room temperature 5 At -7 degrees, there will be condensation on the surface of the laser and the optical lens, which greatly affects the light output efficiency of the laser and the transmission of the optical lens, and greatly affects the laser energy and the service life of the optical accessories. It is recommended that users of Guangda laser cutting machine set the water temperature to 30-32 degrees, and control the temperature difference between the cooling water temperature and the room temperature to be greater than 7 degrees.
2. The temperature rises in summer, and the working pressure of the cooling system of the laser cutting machine increases. It is recommended to check and maintain the internal moderate pressure of the cooler before the high temperature. The pressure of the equipment of different manufacturers is also different. It is recommended to consult the equipment manufacturer before maintenance. parameter.
3. Due to the high temperature in summer, the deterioration rate of the cooling water will also increase. It is recommended that users of laser cutting machines use regular distilled water or pure water and clean up the scale regularly, so as not to cause scale adhesion in the laser and pipes to affect the laser power. Different types of laser cutting machines have different methods for cleaning scale. Please operate under the guidance of the equipment manufacturer.
4. Since the dust of the metal laser cutting machine is mainly metal powder, it is recommended to regularly clean the dust in the electrical cabinet of the laser cutting machine and check the working condition of the cooling fan.
Summary: Scientific and orderly maintenance can effectively avoid some minor problems of the laser cutting machine in use, effectively improve the performance and service life of some accessories, and virtually increase the efficiency of work.
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