After determining which focal length lens to use, the relative position between the focus and the workpiece surface is particularly important to ensure the cutting quality Due to the highest power density at the focus, in most cases, the focus position is just on the workpiece surface or slightly below the surface when cutting Therefore, in the whole cutting process, ensuring the constant relative position between the focus and the workpiece is an important condition to obtain stable cutting quality Sometimes the lens is heated due to poor cooling during operation, resulting in the change of focal length, which requires us to adjust the focus position in time
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 fiber laser cutting machine can obtain the best cutting result In most applications, the beam focus should be adjusted to just under the nozzle. The distance between the nozzle of the fiber laser cutting machine and the workpiece surface is generally about 1.5mm
The influence factor of cutting quality of fiber laser cutting machine is the focus position adjustment. Because the density of laser power has a great influence on the cutting speed, the selection of lens focal length is also a more important problem After the laser beam is focused, the spot size 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 focus 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 allowance is small. It is generally suitable for high-speed cutting of thin materials Because the long focal length lens has this wide focal depth, as long as it has enough power density, it is suitable for cutting thick workpieces