Analysis and control method of factors affecting laser cutting quality

Compared with traditional cutting methods, laser cutting has the characteristics of fast cutting speed, high cutting precision and good processing flexibility. It is widely used for sheet metal cutting. However, due to the complexity of laser cutting, there are many factors that affect the cutting quality, such as laser power, focusing position, nozzle diameter and height. If it is not properly controlled, it is easy to have obvious quality problems such as burrs, burning, and rough cutting surfaces, which cannot meet the actual processing needs. In order to prevent or reduce the occurrence of laser cutting quality problems: before cutting, set relevant process parameters according to the material and thickness of the board; during cutting, once quality problems occur, analyze and find out the factors that cause quality problems, and adjust the relevant processes. Parameters improve processing quality.

We will briefly discuss the main factors affecting the cutting quality and how to properly control the cutting quality.

  1. Laser power

The laser power during cutting mainly depends on the nature of the material being cut and the type of cutting required. However, it can generally be concluded that the greater the power, the greater the thickness of the material that can be cut, and the cutting speed and the width of the slit also increase. The laser power required for different cutting types is gasification cutting>melt cutting>oxygen cutting. Different cutting materials will correspond to the optimal laser power, and the determination of the optimal power needs to be judged by actual cutting and observation. Generally, if the actual power is greater than the optimal power, the heat-affected zone around the incision will expand, and the sharp corners may even partially melt, making it look like a circle, thereby affecting the cutting effect. . When the actual power is less than the optimal power, the roughness of the lower part of the cutting surface becomes worse, and the slag is difficult to remove.

Since the sputtering state of the spark during the cutting process is directly affected by the flow of molten metal in the slit, the determination of the optimal laser power can be judged by the spark state of the sputtering during the cutting process. If the power is properly selected, the state of the spark should be straight and concentrated, slightly lagging, but elongated in the same direction as the cutting direction.

  1. Type of auxiliary gas and its pressure
Gas pressure of fiber laser cutting

The auxiliary gas is usually oxygen, nitrogen, inert gas or compressed air, and the processing quality and processing capacity are affected by the type of gas. When using oxygen as an auxiliary gas, the flammability of oxygen increases the cutting speed and improves the cutting ability, but at the same time, due to the chemical reaction, an oxide film is formed on the surface of the cutting material, which becomes a limitation. Use oxygen. When nitrogen or air is used as an auxiliary gas, the formation of slag can be effectively prevented. In summary, different gas types have different cutting effects and speeds. Oxygen cutting speed is the fastest, nitrogen cutting effect is the best, and air cutting cost is the lowest.

  1. Focus position

The focus position will affect the width of the gap, the slope, the roughness of the cutting surface, the adhesion state of the slag and the cutting speed. Only when the laser obtains the maximum energy density on the surface of the processed material will the melting range be narrowed and high-precision processing can be performed. Regardless of whether the focus moves up or down, the upper gap of the processed material will become wider. The smaller the beam diameter at the focus position, the smaller the depth of focus of the short focal length lens, and the range of the upper cutout changes with the focus position.

  1. Relevant elements of processed materials

When using a laser cutting machine to process materials, on the one hand, the surface condition of the material will affect the absorption stability of the laser beam, on the other hand, the shape of the process will also affect the diffusion of heat.

Material: Different materials have different laser absorption rates, so different materials have different cutting suitability. It should be noted that high reflectivity materials such as copper and aluminum are not conducive to the formation of spots, so the requirements on the cutting machine are higher.

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