Auto-focus function of cutter for metal cutting – Damon

Auto-focus function of cutter. One of the advantages of laser cutting is that the energy density of the beam is high. So the diameter of the focal spot will as small as possible to produce a tiny slit. Because the smaller the focal depth of the focusing lens, the smaller the diameter of the focal spot. For high-quality, high-precision cutting, the effective focal depth is also relatetive to the lens diameter and the material being cut. So it is very important to control the focus and the position of the surface of the cut material.

So what is focus control? When cutting different thickness plates, to show the perfect cutting effect, the focus of the laser beam will set in different places. We call it focusing.

In the early days of laser cutting applications, manual focusing was reliable. However, with the development of laser technology, manual focusing will eventually eliminate. And automatic focusing functions will be popular. For example, high-performance high-speed laser cutting machines have automatic focusing functions. Thus some people will say that the light path integrate into the cutting head. Is it not easy to change the laser height? When the cutting head raise, the focus position is high. And when the cutting head lower down, the focus position is low. However, it turns out that it is not as simple as everyone thinks.

Auto-focus function of cutter

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 to 1.5 mm.  The nozzle height unchange. Therefore, lifting the laser head wouldn’t adjust the focus.

The focal length of the focusing lens is unchangeable. So it is not realistic to adjust the focus by changing the focal length. If the position of the focusing lens change, the focus position also change accordingly. The focus lens goes down, the focus goes down. And the focus lens goes up, the focus goes up. This is really a way to focus. A motor is used to drive the focusing lens for up and down movements to achieve automatic focusing.

Another method of automatic focusing is: Before the light beam enters the focusing mirror, a variable curvature mirror (or tunable mirror) is set. By changing the curvature of the mirror, the divergence angle of the reflected beam is changed, and the focus position is changed.


With automatic focus function, the machine tool can automatically adjust the focus to the appropriate position through CNC when processing workpieces of different materials and thicknesses. This can significantly improve the processing efficiency of the laser cutting machine, and the punching time of thick plates will be greatly reduced. Therefore, for high-speed laser cutter tools, the automatic focusing function is important and indispensable.

All XT laser cutting machines have automatic focusing laser heads. The same laser head can quickly change focusing lenses with different focal lengths, adapt to various power processing, and meet the cutting of different thickness plates. By using the auto-focus function, users can finish cutting or engraving quickly and accurately, which makes the cutting or engraving work more time-saving and improves the user’s work efficiency.