Analysis and solution of burr problem in laser cutting sheet metal parts

Laser cutting is to focus the laser beam on the surface of the material with a focusing mirror to melt, vaporize and ablate the material. At the same time, compressed gas coaxial with the laser beam is used to blow off the molten material, and the laser beam and the material move relatively along a certain trajectory, thus forming a slit with a certain shape and completing the cutting of the material. Laser cutting has the advantages of high precision, narrow slit, smooth cutting surface, high speed, good processing quality and wide processing materials. At present, laser cutting technology has been widely used in many fields. The complete sets of electrical enclosures are mostly made of sheet metal, and laser cutting has become a common processing method in the sheet metal industry because of its low processing cost, high efficiency and many kinds of processing materials. However, the sweet potato is bitter, and there is nothing in the United States. However, the slag and accompanying burrs attached during its processing have annoyed the field managers.

Causes and influence of burr in laser processing
By understanding the working principle and daily practice of laser cutting, it is concluded that there are six main reasons for burr:

(1) The deviation of the upper and lower positions of the laser beam focus leads to energy concentration, insufficient gasification of the workpiece, and the accumulation of slag is not easy to fall off, which is easy to produce burrs;

(2)The output power of laser is not enough to effectively evaporate metal, resulting in a lot of slag and burr;

(3) The type, purity and blowing pressure of the auxiliary gas of the laser cutting machine can not meet the requirements, causing burrs;

(4) The cutting speed of laser cutting is too slow, which destroys the surface quality of the cutting surface and produces burrs;

(5) the working time of the laser cutting machine is too long, which will cause the unstable working state of the equipment and burr;

(6)The laser cutting equipment has some shortcomings, such as the serrated depth of the serrated tray on the laser base is small and the taper is insufficient, so the contact area with the plate is too large, which causes the laser breakdown to be blocked and the gas circulation to be blocked during processing, and it is easy to produce slag adhesion, slag rebound and burr formation.

Burrs in the corners of the workpiece will seriously affect the subsequent bending, welding and assembly accuracy, and there are also certain safety hazards for operators. If the workpiece with burr is applied to the gas box of the ring network cabinet produced by our company, it will have a great influence on the air tightness; When it is used in electrical system, it will also cause short circuit or damage the magnetic field due to burr shedding, which will affect the normal work of the system or bring other hazards.

Methods of preventing burr in laser processing

Adjust equipment parameters
According to different processing materials, the parameters such as power, air pressure, flow rate, focal length and feed speed are repeatedly adjusted to the best state, and the recorded data are saved for subsequent batch processing. It is impossible to cut exquisite workpieces only by relying on the parameters provided by the machine.

Select auxiliary gas
The application of auxiliary gas will also affect the processing quality, so different auxiliary gases should be selected according to different processing materials. For cutting stainless steel, it is recommended to use nitrogen as an auxiliary gas, which is usually called inert gas. During laser processing, nitrogen not only prevents the explosion of laser cutting, but also makes the heated end face not instantly oxidized, and the cut end face will be smoother and brighter. The purity of gas is also very important, so try to choose high purity gas.

Check equipment accessories
For the equipment that has been used for a long time, the processing quality will be reduced and burrs will be produced because of the aging, pollution and damage of its key accessories. If the lens is polluted by oil stains, there are tiny cracks and the cutting nozzle is damaged, the transmission of laser power will be affected. These can be judged by observing whether the formed light spot is round or not. If the light spot is round, it means that the transverse distribution of laser energy is uniform and the cutting quality is high. You can also ensure the cutting quality by regularly checking key components.

Optimize the equipment structure
In actual production, the equipment structure can be improved according to the different workpieces processed. If the contact area between the serrated tray of the laser base and the plate is too large, it is easy to generate burrs. According to the specific situation, the tooth taper can be reduced and the tooth depth can be increased, as shown in Figure 3, so as to avoid interference caused by the excessive contact area between the base and the plate.

Optimize the corner of workpiece
In actual production, it is also found that the corner transition structure of the workpiece will also affect the machining quality. For example, the right-angle transition is more likely to produce burrs than the fillet and bevel transition. As shown in Figure 5, it is suggested to use fillet and bevel transition as much as possible, which can also reduce the stress concentration in the structure.

Under the great environment of developing market economy in China, enterprises are constantly seeking truth from facts and innovating, but at the same time, we can’t ignore the quality problems of the original products. Only by constantly refining and refining the original products and making innovations can we effectively improve our comprehensive competitiveness. The laser cutting machine itself is a precise machine, and its operation is also a delicate work. Often, a data error will cause its abnormal operation. Therefore, only when the equipment, gas and parameters are debugged to the best, can the cutting be more quality.

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