Factors affecting the cutting quality of fiber laser cutting machine focus position adjustment, because the laser power density has a great impact on the cutting speed, the choice of lens focal length is also a relatively important issue. The spot size after the laser beam is focused is proportional to the focal length of the lens. After the beam is focused by the short focal length lens, the spot size is small and the power density at the focus is high, which is beneficial to the cutting of materials.

Since a telephoto lens has a wider depth of focus, it is suitable for cutting thick workpieces as long as it has a density of sufficient power. The relative position of the focal point and the workpiece surface after determining which focal length lens to use is particularly important to ensure the cutting quality. Because of the high power density at the focus, in most cases the focus is just on or slightly below the surface of the workpiece when cutting. Therefore, it is an important condition to keep the relative position of the focus and the workpiece constant in the whole cutting process.

Sometimes the lens is heated due to poor cooling, which may cause the change of focal length. When the focus is at a better position, the slit is small and the efficiency is high. In most applications, the beam focus should be adjusted to just under the nozzle, the fiber laser cutting machine nozzle and the workpiece surface spacing is generally about 1.5mm.