The laser cutting machine focuses the laser light emitted from the laser device into a high power density laser beam through the optical path system. The laser beam irradiates the surface of the workpiece to make the workpiece reach the melting point or boiling point, and at the same time, the high-pressure gas coaxial with the beam blows away the molten or vaporized metal.

With the movement of the relative position of the beam and the workpiece, the material will eventually form a slit, so as to achieve the purpose of cutting.

Laser cutting process replaces the traditional mechanical knife with an invisible beam. It has the characteristics of high precision, fast cutting, not limited to cutting patterns, automatic typesetting saves materials, smooth incision, and low processing cost. It will gradually improve or replace it. Traditional metal cutting process equipment. The mechanical part of the laser cutter head has no contact with the workpiece, and will not scratch the surface of the workpiece during work; the laser cutting speed is fast, the incision is smooth and flat, and generally no subsequent processing is required; the cutting heat-affected zone is small, the deformation of the plate is small, and the kerf is narrow ( 0.1mm~0.3mm); the incision has no mechanical stress, no shearing burrs; high processing precision, good repeatability, no damage to the material surface; CNC programming, can process any plan, and can cut the whole board with a large format without Opening molds is economical and time-saving.

Compared with traditional oxyacetylene, plasma and other cutting processes, laser cutting speed is fast, the slit is narrow, the heat-affected zone is small, the slit edge is vertical, and the cutting edge is smooth. At the same time, there are many kinds of materials that can be cut by laser, including carbon steel , stainless steel, alloy steel, wood, plastic, rubber, cloth, quartz, ceramics, glass, composite materials, etc. With the rapid development of the market economy and the rapid development of science and technology, laser cutting technology has been widely used in the fields of automobiles, machinery, electricity, hardware and electrical appliances. In recent years, laser cutting technology is developing at an unprecedented speed, with an annual growth rate of 15% to 20%. Since 1985, my country has grown at an annual rate of nearly 25%. At present, there is still a big gap between the overall level of my country's laser cutting technology and advanced countries. Therefore, laser cutting technology has broad development prospects and huge application space in the domestic market [1] .

During the cutting process of the laser cutting machine, the beam is focused into a small focal point by the lens of the cutting head, so that the high power density can be achieved at the focal point, and the cutting head is fixed on the z-axis. At this time, the heat input by the beam far exceeds the part of the heat reflected, conducted or diffused by the material, and the material is quickly heated to the melting and vaporization temperature. At the same time, a high-speed airflow will melt from the coaxial or non-coaxial side And the vaporized material is blown out to form holes for material cutting. With the relative movement of the focal point and the material, the hole forms a continuous narrow slit to complete the cutting of the material [1].

At present, the outer optical path part of the laser cutting machine mainly adopts the flying optical path system. The beam emitted from the laser generator passes through the mirrors 1, 2, and 3 to the focusing lens on the cutting head, and after being focused, it forms a spot on the surface of the material to be processed. The reflector 1 is fixed on the fuselage; the reflector 2 on the beam moves in the x direction with the movement of the beam; the reflector 3 on the z axis moves in the y direction with the movement of the z axis. It is not difficult to see from the figure that during the cutting process, as the beam moves in the x direction and the z-axis part moves in the y direction, the length of the optical path changes all the time [1] .

At present, due to reasons such as manufacturing costs, the laser beams emitted by civil laser generators all have a certain divergence angle and are "cone-shaped". When the height of the "taper" changes (equivalent to the change of the optical path length of the laser cutting machine), the cross-sectional area of the beam on the surface of the focusing lens also changes. In addition, light also has the nature of waves, so it is inevitable that there will be diffraction phenomenon, which will cause the beam to expand laterally during propagation. This phenomenon exists in all optical systems and can determine the theory of these systems in terms of performance. limit value. Due to the "cone shape" of the Gaussian beam and the diffraction of light waves, when the length of the optical path changes, the diameter of the beam acting on the lens surface changes moment by moment, which will cause changes in the focal point size and focal depth, but the impact on the focal point position very small. If the focus size and focus depth change during continuous processing, it will inevitably have a great impact on the processing, for example, it will cause inconsistent width of the cutting seam, impenetrable cutting or ablation of the plate under the same cutting power [1] .