Why does the sheet metal fiber laser cutter need automatic focusing?
All we all know, one of the advantages of sheet metal fiber laser cutter is the high energy density of the beam. The focal spot diameter can be as small as possible to produce extremely tiny slits.
In the previous metal cutting applications, the focus of the laser head mainly relied on manual. However, with the continuous development of laser technology, manual focusing was eventually eliminated and replaced by the automatic focusing function. For example, a high-power laser cutting machine has an efficient automatic focusing function.
Some people think that the optical path of the sheet metal laser cutting machine is integrated in the laser head. Can't we simply change the height of the cutting head? For example, when the laser head rises, the focus position is high, and when going down, the focus position is low. However, it turns out that this is not as simple as people think.
First, there is a nozzle at the bottom of the laser head. During the cutting process, the distance between the nozzle and the workpiece (nozzle height) is about 0.5 ~ 1.5 mm, which can be regarded as a fixed value. Thus the nozzle height does not change. So it is impossible to adjust the focus by lifting the laser head.
Secondly, the focal length of the focus lens is constant. So it is unrealistic to adjust the focus by changing the focal length. If you change the position of the focus lens, you must change the focus position accordingly: if the focus lens goes down, the focus point will go down; if the focus lens goes up, the focus point will go up. This is a way of focusing: using a motor to drive the focusing lens to achieve automatic focusing.
Another method is to place a variable curvature mirror (or tunable mirror) before the beam enters the focusing lens, changing the curvature of the mirror to change the divergence angle and focus position of the reflected beam. With the automatic focusing function, when processing workpieces of different materials and different thicknesses, the machine can automatically adjust the focus to a suitable position automatically. This can significantly improve the processing efficiency, and the perforation time of thick plates will also be greatly reduced. Therefore, for high-speed sheet metal laser cutting machine, the automatic focusing function is an important and indispensable function.
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