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Fiber laser cutting machine has many advantages, such as high cutting precision, narrow slit, smooth cutting surface, and high efficiency. At the same time, the use of fiber laser cutting machines has significant advantages in terms of safety and environmental protection. In the future development trend, fiber laser cutting machines will occupy the status of mainstream equipment.
For the cutting difficulties of laser cutting, we need to pay attention to the following matters.
Fast cutting speed is one of the advantages of laser cutting, but the cutting speed is not as fast as possible. In the case of certain laser power, it is necessary to select an appropriate cutting speed according to the cutting plate, so as to make the cutting surface beautiful and obtain high quality. When cutting the workpiece, you can judge whether the cutting speed is appropriate by the following methods, and then adjust the cutting speed.
Watch The Cutting Sparks
When the cutting speed is appropriate, the cutting sparks are more evenly spread from top to bottom; when the cutting speed is too fast, the cutting sparks will tilt; when the cutting speed is too slow, the cutting sparks gather together, do not spread and are less.
Observe The Cutting Sheet
When the cutting speed is appropriate, the cutting surface presents a relatively smooth line, and no slag is produced in the lower half. When the cutting speed is too fast, it may not be able to be cut through, and the sparks may spray randomly; some areas can be cut through, but some areas cannot be cut through; the cutting section is slanted, and the lower part produces slag. When the cutting speed is too slow, it will cause over-melting, the cutting section will be rough, and the kerf will become wider.
Nozzle And Nozzle Height
The nozzle acts as a beam and auxiliary gas channel. The shape, aperture, and nozzle height of the nozzle will affect the cutting effect.
The nozzle is mainly to control the gas diffusion area and size, so as to control the cutting quality; to prevent debris such as slag from rebounding upward, passing through the nozzle, and contaminating the lens. Generally speaking, when cutting thin plates, the defocus amount is small, and small-diameter nozzles are used; while when cutting thick plates, the required slits and spots are large, and large-diameter nozzles are used.
The nozzle is divided into single-layer and double layers. The single-layer laser nozzle is used for melting and cutting, that is, using nitrogen as auxiliary gas to cut stainless steel and aluminum plates, etc.;
The nozzle height is the distance between the nozzle outlet and the workpiece surface. When cutting, we generally set this height at 0.3mm-0.8mm. If it is too low, the nozzle will easily collide with the surface of the workpiece. If it is too high, the concentration and pressure of the auxiliary gas will be reduced, resulting in a decrease in the cutting quality. When perforating, in order to prevent the generated slag from being reflected on the lens, the height of the nozzle can be appropriately raised.
After checking the actual zero focus of cutting through the previous article, in the actual cutting process, we need to set an appropriate focus position to obtain a cutting workpiece with a better cutting effect.
Zero Focal Length
The focus is on the surface of the workpiece and is suitable for cutting thin sheets. The cut surface near the focal point is usually smooth, and the surface far from the focal point is rough. The invention is mainly applied to continuous laser cutting of thin sheets and pulsed laser cutting of high peak power evaporation mold foil.
The choice of cutting point in a laser cutting machine does not depend on the cutting plate material (stainless steel and carbon steel), but on the cutting method (oxidative cutter and fusion cutter).
Negative Focal Length
The focus is under the surface of the workpiece, generally at 1/2-2/3 of the thickness of the workpiece, so the range of the smooth surface is larger, and the slit will be wider than the zero focal length. Because the focal point is far away from the cutting surface, the cutting width is larger than the cutting width of the workpiece, and the required cutting airflow is large enough and the temperature is high enough.
When cutting stainless steel, the negative focus cutting effect is better, the cutting surface is uniform, and the section is good.
Before cutting, since the perforation has a certain height, the use of negative focusing can minimize the spot size on the hole and maximize the energy density. The greater the depth of the hole, the better the negative focusing effect.
Positive Focal Length
The focus is on the upper surface of the workpiece, which is generally suitable for the cutting of thick carbon steel (thick plates require a larger kerf, and a negative focus will cause the carbon steel to overburn). When oxygen cuts carbon steel, the cutting width of the lower cutting surface is larger than that of the upper cutting surface, which is conducive to slag discharge, and the oxygen reaching the lower cutting surface participates in the full oxidation reaction. Within the focal length range, the larger the positive focus, the larger the spot size on the surface of the plate, the more sufficient the preheating and heat source supplementation, and the smoother the carbon steel cutting surface. Difficulties of laser cutting.
10000W pulse laser cutting stainless steel thick plate, positive focusing, stable cutting, conducive to slag discharge, not easy to generate blue light.
Protective Gas Pressure
The size of the auxiliary gas pressure also affects the cutting effect of the fiber laser cutting machine. Adjusting the air pressure can also improve the cutting effect:
Insufficient Air Pressure
When the gas pressure is insufficient, the slag generated by cutting cannot be removed, and it is not easy to penetrate, resulting in slag on the cutting surface; the cutting speed cannot be increased, which affects the cutting efficiency. In general, when cutting thin plates at high speed, high air pressure is required to prevent slag from attaching to the back of the slit; when the material is thicker or the cutting speed is slow, the air pressure can be appropriately reduced.
Air Pressure Too High
Increasing the gas pressure can improve the cutting speed to a certain extent, but the excessive air pressure will actually reduce the cutting speed. This is because, under high pressure, the excessively fast gas flow will enhance the cooling effect, and even interfere with the focusing of the beam energy, resulting in a decrease in cutting quality and efficiency. At the same time, when the air pressure is too high, the cutting surface will be thicker and the kerf will be wider. Difficulties of laser cutting.
Precautions For Starting The Laser Cutting Machine
Close the discharge valve of the air storage tank, turn on the power of the air compressor, and open the valve of the gas delivery pipeline after the pressure of the compressed air reaches the requirement.
Turn on the pre-mixed gas of the laser and adjust the pressure; if the gas of the non-Panasonic laser is mixed in the machine, please turn on the various gases in the following order: helium → carbon dioxide → nitrogen, and set the pressure of each gas to the specified value.
Turn on auxiliary cutting gases (nitrogen and oxygen). When using bottled gas, first open the valve of each bottle, and finally open the general valve switch; when using liquid gas, after opening the valve, you should also open the booster valve to increase the amount of gasification and ensure the pressure of the cutting auxiliary gas.
Turn on the main power switch and start the regulated power supply, check the output voltage of the regulated power supply.
Turn on the chiller and the dryer.
Turn on the power of the control cabinet of the machine tool, release the emergency stop button and turn on the key switch, and enter the operation interface after the start of the numerical control system. When turning on the power of the machine control cabinet, the laser power can be turned on, and the low voltage and high voltage can be started in sequence. And turn the “mode selection” key switch to the external control mode. Difficulties of laser cutting.
Precautions For Turn Off The Laser Cutting Machine
First, move the cutting head to the highest point, and stop the X and Y axes at the safe position. Swap the bench or stop the bench in a safe location.
Turn off the high voltage of the laser, turn off the low voltage of the laser, wait for about 3 minutes and then turn off the main power of the laser. Turn off all key switches on the laser cabinet and remove them for safekeeping.
Press the emergency stop button on the control panel side of the machine tool, turn off the key switch, and remove the key for storage. Exit the operation page of the CNC system, and then turn off the power of the main control cabinet of the machine tool when the page prompts you to turn off the power.
Turn off the power of the chiller and the dryer.
Turn off the regulated power supply.
Turn off all cutting auxiliary gases and then turn off the laser gas.
Turn off the air compressor power and open the air tank discharge valve.
Excellent cutting equipment is selected and inspected before cutting is done. The process parameters of laser cutting must be adjusted according to the actual situation during cutting. In specific applications, the most suitable cutting parameters should be selected according to the situation. Every time we optimize the cutting process in production is also an important means to maintain long-term stability and leadership. Difficulties of laser cutting.