High power laser cutting technology is a composite advanced manufacturing technology integrating laser optics, electronics, machinery, technology and materials. The laser cutting process is complex and affected by many factors, including laser output power, cutting speed, defocusing amount and cutting material properties. If the process parameters are selected improperly, the cutting quality will be greatly affected, such as rough cutting surface, notch in the section or slag adhesion on the back, etc. 1. Cutting speed Generally, the cutting speed is to select a lower value within the upper and lower limits of the speed. Too high or too low speed will affect the cutting quality, resulting in slag hanging or even impervious cutting. When the cutting speed is too low, the laser energy density is too large, and the heat affected zone becomes larger, which will lead to more slag hanging, wide and rough cutting seams. When the cutting speed is too high, the laser energy density is small, which may not cut through. The notch perpendicularity and slag hanging height are the most sensitive to the speed parameters, followed by the notch width and surface roughness. Operations that can increase the cutting speed include: ● increase power ● change beam mode ● reduce the size of the focus spot (such as using a short focal length lens) 2. Focus position After the laser beam is focused, the spot size is proportional to the length of the lens. After the beam is focused by a 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 material cutting; But its disadvantage is that the focal depth is very short and the adjustment allowance is very small. It is generally suitable for high-speed cutting of thin materials. For thick workpiece, because the long focal length lens has a wide focal depth, as long as it has sufficient power density, it is more suitable to cut it. Because the power density at the focus is the highest, in most cases, when cutting, the focus position is just on the workpiece surface, or slightly below the workpiece surface. Ensuring that the relative position between the focus and the workpiece is constant is an important condition for obtaining stable cutting quality. Sometimes the lens is heated due to poor cooling during operation, resulting in changes in focal length, which requires timely adjustment of the focus position. 3. Auxiliary gas Laser cutting will produce a lot of heat, so high heat together, will make the cutting material burning, oxidation reaction, and easy to deform the workpiece. Therefore, it is necessary to add some auxiliary gases, generally including oxygen, air and nitrogen. The auxiliary gas is sprayed coaxially with the laser beam to protect the lens from pollution and blow away the molten slag at the bottom of the cutting area. For non-metallic and some metallic materials, compressed air or inert gas is used to remove the melted and evaporated materials, while restraining the excessive combustion in the cutting area. 4. Auxiliary gas pressure During laser cutting, the gas and the focused laser beam are shot to the cut material through the nozzle. Thus, an air flow beam is formed. The basic requirement for air flow is that the air flow into the incision should be large and the speed should be high, so that enough oxidation can make the incision material fully conduct exothermic reaction, and at the same time, there is enough momentum to spray and blow out the molten material. Most metal laser cutting uses active gas (oxygen) to form an oxidative exothermic reaction with the hot metal. This additional heat can increase the cutting speed by 1/3 to 1/2. 5. Laser output power The size of the laser power has a considerable impact on the cutting speed, slit width, cutting thickness and cutting quality. The power required by the laser cutting machine is based on the characteristics of the material and the cutting mechanism. The ideal cutting speed will make the cutting surface show relatively stable lines, and the lower part of the material will not show slag. In practice, the maximum power is often set to obtain high cutting speed or to cut thick materials.