After determining which focal length lens to use, the relative position of the focus and the workpiece surface is particularly important to ensure the cutting quality. Because the power density at the focus is the highest, in most cases, When cutting, the focus position is just on the surface of the workpiece or slightly below the surface. Therefore, ensuring that the relative position of the focus and the workpiece is constant throughout the cutting process is an important condition for obtaining stable cutting quality. Sometimes the lens is heated due to poor cooling during operation, resulting in changes in the focal length, which requires us to adjust the focus position in a timely manner

When the focus is at the best position, the slit is the smallest and the efficiency is the highest. The best cutting speed of the optical fiber laser cutter can obtain the best cutting result. In most applications, the beam focus should be adjusted to just under the nozzle. The distance between the optical fiber laser cutter nozzle and the workpiece surface is generally about 1.5mm

The focus position adjustment, which affects the cutting quality of the optical fiber laser cutting machine, is also an important issue because the laser power density has a great impact on the cutting speed. The focal length of the lens is also an important issue. The size of the focused spot of the laser beam is proportional to the focal length of the lens. After the beam is focused by the short focal length lens, the spot size is very small, and the power density at the focal point is very high, which is very beneficial to the cutting of materials; However, its disadvantage is that the focal depth is very short and the adjustment margin is small, which is generally suitable for high-speed cutting of thin materials. Because the long focal length lens has such a wide focal depth, it can be suitable for cutting thick workpieces as long as it has enough power density