Laser cutting machines must master and solve several key technologies for cutting parts with high precision or large thickness. The focus position control technology is one of them. One of the advantages of laser cutting is the high energy density of the beam, so the diameter of the focal spot should be as small as possible to produce a narrow slit. Because the smaller the focal depth of the focusing lens, the smaller the diameter of the focal spot. For high-quality cutting, the effective focal depth is also related to the lens diameter and the material being cut. Therefore, controlling the position of the focus relative to the surface of the material being cut is very important. How to use a laser cutting machine to cut high-quality products?
Due to the significant impact of laser power density on cutting speed in vibration knife cutting machines, the selection of lens focal length is an important issue. After focusing the laser beam, the size of the spot is proportional to the focal length of the lens. After focusing the beam through a short focal length lens, the size of the spot is very small, and the power density at the focal point is high, which is beneficial for material cutting; But its disadvantage is that the depth of focus is very short and the adjustment margin is small, which is generally suitable for high-speed cutting of thin materials. Due to the wide focal depth of long focal lenses, as long as they have sufficient power density, they are more suitable for cutting thick workpieces.
After determining which focal length lens to use, the relative position between the focal point and the workpiece surface is particularly important for ensuring cutting quality. Due to the highest power density at the focal point, in most cases, the focal point is just on the surface of the workpiece or slightly below the surface during cutting. Ensuring a constant relative position between the focus and the workpiece is an important condition for achieving stable cutting quality throughout the entire cutting process. Sometimes, due to poor cooling during lens operation, heating can cause changes in focal length, which requires timely adjustment of the focal position.
When the focus is in the optimal position, the cutting seam is the smallest and the efficiency is the highest, and the optimal cutting speed can obtain the best cutting result. In most applications, laser cutting machines adjust the beam focus to just below the nozzle. The distance between the nozzle and the surface of the workpiece is generally about 1.5mm.