The focus position adjustment is an important factor affecting the cutting quality of the fiber laser cutting machine. Since the laser power density has a great impact on the cutting speed, the selection of lens focal length is also an important issue. The size of the spot after the laser beam is focused is proportional to the focal length of the lens. After the laser beam is focused by a short focal length lens, the size of the spot is very small, and the power density at the focal point is very high, which is very beneficial to the material cutting; However, its disadvantage is that the focal depth is very short and the adjustment allowance is small, which is generally applicable to high-speed cutting of thin materials. Because the long focal length lens has this relatively wide focal depth, as long as it has enough power density, it is suitable for cutting thick workpiece.
The relative position of the focus and the workpiece surface is particularly important to ensure the cutting quality after determining the lens of which focal length to use. Due to the high power density at the focus, in most cases, the focus position is just on the surface of the workpiece or slightly below the surface when cutting. Therefore, it is an important condition to obtain stable cutting quality to ensure that the relative position of the focus and the workpiece is constant during the whole cutting process. Sometimes the lens is heated due to poor cooling during operation, resulting in changes in focal length, which requires us to adjust the focus position in time.
When the focus is in the right position, the cutting seam is small and the efficiency is high. The cutting speed of the fiber laser cutting machine can obtain good cutting results.
In most applications, the beam focus should be adjusted to just below the nozzle, and the distance between the nozzle of the fiber laser cutting machine and the workpiece surface is generally 1. About 5mm.