Compared with traditional acetylene, plasma and other cutting processes, the laser cutting speed is fast, the slit is narrow, the heat affected zone is small, the edge of the slit is good, the trimming is smooth, and there are many kinds of materials that can be laser cut, 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, electric power, hardware and electrical appliances. In recent years, laser cutting technology is growing at an unprecedented rate, growing at a rate of 15% to 20% per year. Since 1985, China has grown at a rate of nearly 25% per year. At present, the overall level of laser cutting technology in China still has a big gap compared with advanced countries. Therefore, laser cutting technology in the domestic market has broad development prospects and huge application space.
During the cutting process of the laser cutting machine, the beam is focused by the lens of the cutting head into a small focus, which achieves a high power density at the focus, wherein the cutting head is fixed on the z-axis. At this point, the heat input by the beam far exceeds the amount of heat that is reflected, conducted, or diffused by the material, and the material is quickly heated to the melting and vaporization temperatures, while a high velocity gas stream is melted from the coaxial or non-coaxial side. The vaporized material is blown out to form a hole in which the material is cut. With the relative movement of the focus and the material, the holes are formed into a continuous slit having a narrow width to complete the cutting of the material.
At present, the outer optical path portion of the laser cutting machine mainly uses a flying optical path system. The beam emitted from the laser generator passes through the mirrors 1, 2, 3 to the focusing lens on the cutting head, and after focusing, a spot is formed on the surface of the material to be processed. The reflective lens 1 is fixed on the fuselage; the mirror 2 on the beam moves in the x direction along with the movement of the beam; and the mirror 3 on the z axis moves in the y direction along 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, the z-axis portion moves in the y direction, and the length of the optical path changes at all times.
At present, due to the manufacturing cost and the like, the laser beam emitted by the civilian laser generator has a certain divergence angle and is "conical". When the height of the "taper" changes (equivalent to the change in the optical path length of the laser cutter), the beam cross-sectional area of the focus lens surface also changes. In addition, light also has the properties of waves. Therefore, diffraction phenomenon will inevitably occur. Diffraction will cause the beam to spread laterally during propagation. This phenomenon exists in all optical systems and can determine the theory of performance of these systems. Limit value. Since the Gaussian beam is "conical" and the diffraction of the light wave, when the length of the optical path changes, the diameter of the beam acting on the surface of the lens changes at a moment, which causes a change in the focus size and depth of focus, but the influence on the focus position. Very small. If the focus size and depth of focus change during continuous processing, it will inevitably have a great impact on the processing, for example, it will result in inconsistent slit width, can not cut through the same cutting power or ablate the sheet, etc.