Now let’s talk about focus control before talking about auto focus. Users who are familiar with high-speed laser cutting machine tools know that when high-speed laser cutting is used to cut sheets of different material thicknesses, the focus of the laser beam will be set to show a good cutting effect. In different places, it is called what we call focusing.
Everyone does not know that in the application of laser cutting, focusing depends on manual operation. With the development of laser technology, manual focusing will eventually be eliminated. Instead, automatic focusing will be explored. For example, high-performance high-speed laser cutting machine tools have high-efficiency and comprehensive Auto focus function. So, some people will say that the optical path is integrated in the cutting head, can’t simply change the laser height? When the cutting head is raised, the focal position is higher, and when the cutting head is lowered, the focal position is lower. However, it turns out that it is not as simple as everyone thought.
The bottom of the cutting head is a nozzle. During the cutting process, the distance between the nozzle and the workpiece (nozzle height) is about 0.5~1.5mm. It may be regarded as a fixed value, that is, the nozzle height is unchanged, so it cannot be adjusted by lifting the laser head. Coke.
Then the focal length of the focusing lens cannot be changed, so it is not practical to adjust the focus by changing the focal length. If you change the position of the focus lens, the corresponding is to change the focus position: the focus lens goes down, the focus goes down, and the focus lens goes up, the focus goes up. This is indeed a way of focusing. A motor is used to drive the focusing lens to move up and down to achieve automatic focusing.
Another automatic focusing method is: before the beam enters the focusing mirror, set a variable curvature mirror (or adjustable mirror), by changing the curvature of the mirror, changing the divergence angle of the reflected beam, and changing the focus position. With the automatic focusing function, when processing workpieces of different materials and thicknesses, the machine can automatically adjust the focus to a suitable position automatically by means of numerical control. This can significantly improve the processing efficiency of high-speed laser cutting machine tools, and the thick plate perforation time will also be greatly reduced.
For high-quality, high-precision cutting, the effective focal depth is also related to the lens diameter and the material to be cut, so it is very important to control the focus and the position of the material surface. Therefore, for high-speed laser cutting machine tools, the automatic focusing function is an important and indispensable function.