Laser processing technology is a complex advanced manufacturing technology which integrates optics, mechanics, electricity, material processing and testing. The high-efficiency automatic processing equipment combined with modern numerical control technology can break through many technical bottlenecks that cannot be realized by traditional manufacturing methods. It plays an irreplaceable role in the pillar industries of national economy, such as energy, transportation, iron and steel metallurgy, shipbuilding and automobile manufacturing, electronic and electrical industry, aerospace and other pillar industries.
Automobile, ship, aviation, aerospace, steel, energy and other Chinese industries are in urgent need of laser cutting equipment, especially high-end equipment, so it is very important to improve the manufacturing level of laser cutting equipment in China. It can not only meet the domestic market demand, break the foreign technology monopoly in this field, but also promote the progress of laser cutting technology in China. To achieve higher speed, high precision and intelligent laser cutting will be the goal of CNC machine tool cutting machine technology development.
The use of laser cutting machine has entered thousands of households, but its quality sometimes also varies, so how to distinguish its quality?
The quality of laser cutting machine is affected by various factors. In order to obtain the ideal cutting quality, each cutting parameter is limited in a narrow range. It is necessary to explore the reasonable cutting parameters under different conditions by repeated experiments. It is not only time-consuming and laborious, but also unable to respond to the disturbance factors in the cutting process. How to quickly find the optimal cutting parameters under different cutting conditions and keep them stable in the cutting process is particularly important. Therefore, it is necessary to study the method of on-line monitoring and real-time control of laser cutting quality.
The main index of high-quality laser cutting is no cutting defects, the cutting surface roughness value is small, so the real-time monitoring target should be able to identify cutting defects and monitor the information reflecting the cutting surface roughness, among which the most important and the most difficult is to obtain the roughness information.
In the aspect of cutting surface roughness monitoring, an important research achievement is to find that the main frequency of the fluctuation spectrum of the light radiation signal at the cutting edge is equal to the frequency of the cutting stripe on the cutting surface, and the frequency of the cutting stripe is related to the roughness of the cutting surface. The characteristics of this method are that the monitoring equipment and signal processing system are simple and the monitoring and processing speed is fast
Further research shows that the consistency between the main frequency of the cutting front light radiation signal and the upper fringe frequency of the cutting surface is limited to the range of the lower cutting speed. When the cutting speed is greater than a certain value, the main frequency of the signal disappears, and no information related to the cutting fringe can be found.
Therefore, it is difficult to obtain valuable roughness information of cutting surface, especially near the lower edge, under the normal cutting speed. The more comprehensive and abundant information about the cutting defects and the roughness of the cutting surface can be obtained by using the vision sensor to monitor the images of both the surface and the spark cluster. In particular, the spark shower from the lower end of the cutting seam is closely related to the quality of the lower edge of the cutting surface, which is an important information source for obtaining the roughness of the lower edge of the cutting surface.
The frequency spectrum and main frequency of the laser cutting machine front edge radiation signal are only related to the cutting stripe on the upper part of the cutting surface, and do not reflect the situation of the lower cutting stripe, so the obtained information is not the most valuable information. Because the general cutting surface (except for the cutting of very thin plate) is divided into upper and lower parts, the upper cutting stripe is neat, tie MI, and the roughness is small; the lower the cutting stripe is disordered, the roughness is large, and the lower it is, the rougher it is, and reaches the maximum roughness value near the lower edge. It is unreasonable and unreliable to use the detection signal as the basis of cutting quality evaluation and control.
The data are for reference only