Compared with traditional oxyacetylene and plasma cutting technologies, laser cutting speed is fast, the slits are narrow, the heat affected zone is small, the verticality of the slit edges is good, and the trimming edge is smooth. At the same time, there are many types 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 advancement of science and technology, laser cutting technology has been widely used in automobiles, machinery, power, hardware and electrical appliances. In recent years, laser cutting technology has been developing at an unprecedented rate, with an annual growth of 15% to 20%. Since 1985, our country has grown at a rate of nearly 25% per year. At present, the overall level of laser cutting technology in China is still quite different from that of advanced countries. Therefore, laser cutting technology in the domestic market has broad prospects for development and a huge application space.
During the cutting process of the laser cutting machine, the light beam is focused by the lens of the cutting head into a very small focal point, so that the power density reaches a high power density, wherein the cutting head is fixed on the z-axis. At this time, the input heat of the beam far exceeds part of the heat reflected, conducted or diffused by the material. The material is quickly heated to the melting and vaporization temperature. At the same time, a high-speed air stream will melt 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 focal point and the material, the hole is formed into a continuous narrow slit and the material is cut.
For the cutting machine of the flying light path, due to the divergence angle of the light beam, the length of the light path is different when cutting the near end and the far end, and the beam size before the focusing has a certain difference. The larger the diameter of the incident beam, the smaller the diameter of the focal spot. In order to reduce the change of focal spot size brought about by the change of the beam size before focusing, manufacturers of laser cutting systems at home and abroad provide some special devices for users to choose:
(1) Parallel light pipe. This is a common method, which is to add a collimator at the output end of the CO2 laser to expand the beam. The diameter of the expanded beam becomes larger and the divergence angle becomes smaller, so that the proximal and distal ends of the cutting range can be achieved. The beam size is nearly uniform before focusing.
(2) Add a separate lower axis of the moving lens to the cutting head, which is a separate part from the Z axis that controls the stand off of the nozzle to the material surface. When the machine table moves or the optical axis moves, the beam also moves from the near end to the far end F axis, so that the spot diameter remains the same throughout the entire processing area after the beam is focused. As shown in Figure 2.
(3) Control the water pressure of the focusing mirror (usually a metal reflective focusing system). If the size of the focal spot diameter becomes large as the size of the beam before focusing becomes smaller, the water pressure is automatically controlled to change the focal curvature so that the focal spot diameter becomes smaller.
(4) Increase the x and y direction compensation light path system on the flight light path cutting machine. That is, when the cutting of the distal optical path increases, the compensating optical path is shortened; on the other hand, when the cutting of the proximal optical path decreases, the compensating optical path is increased to keep the optical path length uniform.