Five-axis machining means that there are at least five coordinate axes (three linear coordinates and two rotating coordinates) on a machine tool, and it can coordinate motion simultaneously under the control of computer numerical control (CNC) system. Compared with general three-axis NC machining, such five-axis NC machining has the following advantages: First, it can process continuous and smooth free-form surface that general three-axis NC machining can not process or is difficult to complete processing in one clamp. For example, blades of aero-engines and steam turbines, helical thrusters for warships, and many shells and dies with special surfaces and complex cavities, holes, etc., such as ordinary three-axis NC, because the position and attitude angle of the cutter relative to the workpiece can not be changed in the process of machining, interference or undermachining may occur when machining some complex free-form surfaces. 。 When machining with a five-axis machine tool, because the position and pose angle of the tool/workpiece can be adjusted at any time during the processing, the interference of the tool/workpiece can be avoided and the whole processing can be completed at one time. Secondly, the machining accuracy, quality and efficiency of the space free-form surface can be improved. For example, when machining complex curved surface with three-axis machine tools, ball-end milling cutter is mostly used. The ball-end milling cutter is formed by point contact, the cutting efficiency is low, and the position and orientation angle of the cutter/workpiece can not be adjusted in the process of machining. It is generally difficult to ensure that good cutting points on the ball-end milling cutter (i.e. higher linear speed points on the ball-end) are used for cutting, and it is possible that cutting points fall on the linear speed of the ball-end cutter, etc. The situation on the center line of rotation at zero. Five-axis machine tool can not only avoid this situation, but also make full use of the excellent cutting points of the tool, or replace the ball-end milling cutter formed by point contact with spiral end milling cutter formed by line contact, or even optimize the position and orientation angle of the cutter/workpiece by further optimizing the position and orientation angle of the cutter/workpiece. Cutting, so as to obtain higher cutting speed, cutting line width, that is, to obtain higher cutting efficiency and better surface quality. Third, the advantages of die processing. In the traditional die processing, the vertical machining center is usually used to finish the milling of the workpiece. With the continuous development of die manufacturing technology, some weaknesses of vertical machining center itself are becoming more and more obvious. Ball-end milling cutter is widely used in modern die processing. It brings obvious benefits in die processing. But if vertical machining center is used, the linear velocity of the bottom is zero, so the finish of the bottom is very poor. If the four-axis and five-axis linkage machine technology is used to process the die, the above shortcomings can be overcome. Using five-axis linkage machine tool to process the die can quickly complete the die processing, fast delivery, better guarantee the quality of the die processing, make the die processing easier, and make the die modification easier. To strengthen the importance of five-axis linkage technology in die and mould industry, China should catch up with or surpass developed countries in manufacturing industry. On the basis of vigorously developing its own CNC and die industry, China should actively promote the application of high-grade CNC equipment, including appropriate imports of advanced CNC machining centers from abroad. Because the high-grade CNC machine tools and moulds are at the front of the manufacturing industry chain. The quality of die and mould products, to a large extent, is also subject to numerical control processing equipment. Five-axis linkage is the representative of high-end numerical control. For a long time, the developed western industrial countries, led by the United States, have taken the five-axis CNC machine tool system as an important strategic material and implemented the export licensing system. Developing countries not only have difficulties in production and research, but also have great resistance in importing five-axis CNC machine tools. The reason is that it can process mechanical parts with complex curved surfaces, especially in solving impellers, blades, marine propellers, crankshafts of large diesel engines and other aspects with unique advantages. Therefore, high-precision CNC machine tools have a decisive influence on the military, aerospace, precision medical equipment, scientific research, precision instruments and other industries of a country, which can be called "the soul of manufacturing industry". Modern CNC machine tools are developed by developed countries such as the United States, Japan, Germany and so on. Therefore, from the current situation, the imported technology content is relatively better than domestic, but the quality of products developed by some domestic enterprises is also catching up. On the basis of introducing foreign advanced technology and equipment appropriately, we should pay attention to digestion and absorption and steadily develop our own high-end CNC industry. To rely on imports blindly will surely make China's manufacturing industry be subjected to the whole national economy. But any kind of scientific and technological progress in human history is developed on the shoulders of giants. To abandon the existing science and technology in other countries is undoubtedly a kind of conceited idea of making cars behind closed doors and being arrogant at night.