Abstract: This paper introduces the latest developments in ultra-high-speed machining tools and cutting tools. Several key technologies of ultra-high-speed machine tools are discussed, including high-speed spindle units, high-speed spindle bearings, linear motor feed drive systems, high-speed machine tool control systems, and high-speed machining tools. The development of ultra-high-speed machine tool and cutting tool technology in China is also discussed. Keywords: High-speed machine tool, high-speed spindle, linear motor, high-speed cutting tool. Ultra-high-speed machining refers to cutting operations performed at speeds five to ten times higher than conventional cutting speeds. For example, in the laboratory, aluminum alloy machining has reached 6000 m/s; while in actual production, it has reached 1500–5500 m/s. In the laboratory, the grinding speed of a single-layer coated wheel reaches 300 m/s, and grinding speeds of 500 m/s are currently being explored; while in actual production, it has reached 250 m/s. Ultra-high-speed machining can not only significantly improve the machining efficiency of parts, shorten machining time, and reduce machining costs; but also enable parts to achieve higher levels of surface finish and machining accuracy. I. Spindle Machining Unit of High-Speed ​​Machine Tools The high-speed spindle unit is the most critical component of high-speed and ultra-high-speed machine tools. Its main type is the electric spindle. Abroad, electric spindles equipped with various advanced electrical drive and control technologies have achieved specialized production and commercial supply, such as the electric spindles produced by Fisher in Switzerland. These technologies include variable displacement drives that enable near-stop operation, optimized vector control with speed change accuracy within 0.5%, and vector control with C-axis functionality. These spindle units offer more than ten specifications of spindle sleeve outer diameters ranging from 33-250 mm. The maximum speed reaches 18,000 m/min, and the maximum power can reach 70 kW. At EN097, electric spindles were the most popular functional component in machine tool manufacturing technology, with 76 exhibitors. Furthermore, Step-Tec, a member of the renowned Swiss machine tool manufacturer Micron, specializes in the production of electric spindle components. Various ultra-high-speed bearings have been successfully used in high-speed spindle systems. These bearings require high rigidity and load-bearing capacity during spindle rotation, as well as a long service life. This type of bearing is a high-precision ceramic ball angular contact bearing, magnetic bearing, and hydrostatic/hydrodynamic bearing. To reduce centrifugal force during high-speed rotation, the rolling elements in this high-precision ceramic ball angular contact bearing are made of hot-pressed silicon nitride (SiN4) ceramic material, while the inner and outer rings remain bearing steel. This bearing has a dense ball structure with a contact angle of 15°, and it is a retainer with an outer diameter centering mechanism. Two ceramic bearings are mounted back-to-back at the front and rear supports. The n value of this bearing exceeds 2 x 10⁶ mm·r/rain. The ceramic balls have low density and low centrifugal force; high stiffness; low heat generation; good thermal stability; and long service life. To increase the wear resistance of the bearing raceway, a coating or other surface treatment can be applied. This bearing can increase the rotational speed by more than 50% compared to similarly sized bearings, reduce temperature rise by 35%-60%, and has an elastic modulus 1.5 times that of bearing steel. The limiting speed of this bearing is closely related to its lubrication method, generally employing oil-air lubrication or oil spray lubrication. Oil-air lubrication is a mixture of air and other substances. Compressed air (from the factory air source, filtered through a fine filter) is supplied continuously, while oil (with some additives added by a few manufacturers) is supplied in a timed, minimum-quantity supply. The limiting speed of oil-air lubricated bearings can reach (1.8～2.1)×10⁶/min. The limiting speed of oil-spray lubricated bearings can reach (2.3-2.5)×10⁶/min, but this lubrication method pollutes the environment. Both of these lubrication methods require specialized lubrication devices. Generally, labyrinth lubrication and compressed air external blowing are used. Fluid hydrostatic bearings are also widely used in high-speed spindle systems. The American company K-Mou uses fluid hydrostatic bearings in its HvM8∞ high-speed machining center, where the spindle speed can exceed 20,000 r/min, and the journal surface circumferential speed reaches 50 m/s. The bearings are characterized by high pressure, large clearance, and small-hole throttling. Since the 1990s, foreign countries have invested heavily in developing high-speed hydrostatic bearings, conducting extensive research on their stiffness, load-bearing capacity, temperature rise, and stability. Currently, the United States has launched high-speed liquid hydrostatic bearings with spindle speeds exceeding 40,000 r/min, using water as lubricant. The design and manufacturing technology of high-speed liquid hydrostatic bearings is mature abroad. Simultaneously, the integration technology of high-speed hydrostatic bearings with spindle systems is also under development. Magnetic levitation bearings are favored due to their unparalleled advantages. Magnetic levitation bearings can achieve a Dmn value of 4 × 10⁶ mm/min, a load-bearing capacity of 300 kN, an axial static stiffness of 2000 N/µm, a dynamic stiffness of 100 N/µm, and a reliability exceeding 4000 h. The spindle unit manufactured by the Swiss company Ibag, using magnetic levitation bearings, can achieve spindle speeds of 201,300–40,000 r/min, with a maximum of 200,000 r/min. The German company KAPP uses magnetic levitation bearing grinding wheel spindles with speeds up to 60,000 r/min. Currently, three companies—Ibag, GNN, and Seiko-Seiki of Japan—supply electric spindles with magnetic levitation bearings. In summary, currently, high-speed, high-power spindle units use ceramic hybrid ball bearings or liquid hydrostatic bearings based on functional and economic requirements. However, with the development of even higher spindle speeds, magnetic levitation bearings are a research and application area that research institutions and manufacturers are increasingly focusing on. II. Feed Drive System of High-Speed ​​Machine Tools Ultra-high-speed machine tools require feed systems with high-speed feed motion corresponding to the high spindle speed (even higher traverse speed during idle stroke). Linear motor drives achieve contactless direct drive, avoiding the shortcomings of ball screw (gear, rack) transmissions such as backlash, inertia, friction, and insufficient rigidity, achieving high-precision high-speed movement with excellent stability. Ingersoll, an American company that pioneered the use of linear feed motors, employed permanent magnet linear motors on the x, y, and z axes of its I-WN8 machining center, achieving a maximum feed speed of 76.2 m/min. Vigolzone, an Italian company, produced a high-speed horizontal machining center with linear motors on all three axes, achieving feed speeds of 70 m/min and accelerations up to 1gc. Extcell-0, a German company, produced the XHC24 horizontal machining center, using linear drive motors from I, achieving a maximum feed speed of 60 m/min and an acceleration of 1gc. At CIMT97, Siemens, a German company, demonstrated a high-speed feed of 120 m/min using linear motors. Siemens' linear motors achieved a maximum feed speed of 2000 m/min, a maximum thrust of 6600 N, and a maximum displacement of 504 mm. Currently, linear motors can achieve accelerations exceeding 2g. Additionally, Mazak, a Japanese company, also holds a significant market share in linear motors. III. Control Systems of High-Speed ​​Machine Tools Currently, spindle motor design is still based on existing vector-controlled variable frequency speed-regulating AC motors, optimizing existing technologies, utilizing more complex and higher-performance semiconductor devices and faster processors, and further optimizing vector control technology. In high-speed machine tools, digital spindle control systems and digital servo axis drive systems should have ultra-high-speed response characteristics. The spindle unit control system, in addition to requiring high-speed response characteristics when controlling the spindle motor, should also have good dynamic response characteristics for the spindle support system. When using hydraulic or magnetic levitation bearings, it should be able to automatically adjust relevant parameters according to different machining materials, different tool materials, and dynamic changes in the machining process. The workpiece machining monitoring device should use monitoring elements with high tracking characteristics and resolution, such as dual-frequency laser interferometers. The feed linear motor control system utilizes existing variable frequency speed regulation and vector control technologies and is continuously improving. In high-speed machining, the input control program is still the standard ISONC code. However, traditional NC programs have many problems under high-speed conditions, such as the need for special programming methods to make cutting data suitable for the power characteristic curve of high-speed spindles; and how to solve the reliability problem of high-speed communication between CAD and CAM during high-speed machining. These issues require further research and solutions. IV. High-Performance Tool System Technology For rotary tools (including grinding wheels) mounted on ultra-high-speed spindles, the structural safety and high-precision dynamic balance of the tool are crucial. When the spindle speed exceeds 10,000 r/min, on the one hand, the centrifugal force causes the traditional 7:24 taper port of the spindle to expand, reducing the tool's positioning accuracy and connection rigidity, increasing vibration, and even causing seizing at the connection. On the other hand, the reliability of commonly used insert clamping mechanisms decreases, and the impact of the overall tool imbalance is amplified (proportional to the square of the speed). To address this, Germany developed the HSK (short taper hollow shank) connection method and a system technology for graded tool balancing and automatic spindle balancing. The HSK connection has high contact stiffness, reliable clamping, and high repeatability, making it suitable for ultra-high-speed spindles of 20,000–46,000 r/min. The automatic spindle balancing system can reduce vibration caused by residual tool imbalance and fit errors by more than 90%. In recent years, many tools suitable for ultra-high-speed cutting have been developed, employing high-strength tool body materials and simple, safe tool body structures with fewer parts, while also possessing shorter cutting edges, larger tool tip angles, stronger chip-breaking capabilities, and optimized cutting geometry. Currently, some tooling companies can provide ultra-high-speed tools with HSK interfaces and different balancing accuracies, such as KOMET and SAD-VIC, which are already used in high-speed machining of aircraft and automobiles. [b]V. Machine Tool Support Technology and Auxiliary Unit Technology[/b] Machine tool support technology mainly refers to the design and manufacturing technology of machine tool support components. Auxiliary unit technology includes rapid workpiece clamping technology, machine tool safety devices, high-efficiency coolant and lubricant filtration systems, cutting processing, and workpiece cleaning technology. The machine tool's bed, column, and base, and other supporting foundation components, require good static stiffness, dynamic stiffness, and thermal stiffness. For precision high-speed machine tools, both domestic and international manufacturers use polymer concrete (artificial granite) to manufacture the bed and column. Some use cast iron for the column and base, while others use welded steel plates, filling the internal cavity with damping material to improve vibration resistance. The results are very good. VI. Development of High-Speed ​​Machine Tool Technology in China Chinese institutions have also made significant progress in the research and development of ultra-high-speed machine tool processing technology. Shenyang Institute of Technology has achieved phased results in the development of ultra-high-speed milling and turning machines. Beijing Machine Tool Research Institute has produced a vertical machining center with a spindle speed of 8000 r/min and a power of 7 kW. Tongji University and Guangdong University of Technology have conducted systematic research on the dynamic characteristics of spindle units and the application technology of linear motors, respectively. Northeastern University has studied hot-pressed silicon nitride ceramic ball bearings and established an ultra-high-speed grinding experimental platform capable of conducting grinding tests at 200 m/s. VII. Development Trends of Ultra-High-Speed ​​Machine Tools With the updating of manufacturing concepts and the comprehensive progress of manufacturing technology, ultra-high-speed cutting and ultra-high-speed machine tools will achieve new developments in the following aspects: (1) Achieving green ultra-high-speed cutting in dry or semi-dry cutting conditions. Using semi-dry cutting methods with minimal atomized lubrication or minimal cutting will fundamentally improve the cutting environment and meet the relevant environmental protection standards (Lu014000 series) for industrial production. At the same time, it will save direct investment in cutting and waste liquid treatment and environmental protection costs. Tool technology is the key to achieving this goal. (2) Performing ultra-high-speed cutting in heavy cutting processes. This plays a very important role in improving the production efficiency of large and medium-sized equipment manufacturing in China. For example, a lathe of Nippon Koki 5NK can perform ultra-high-speed machining of large rolls, which is 5 times more efficient than ordinary machining. (3) Developing and improving various ultra-high-speed cutting processes, such as ultra-high-speed L-machining. Ultra-high-speed lathes have higher and more reliable dynamic characteristics and automatic balancing capabilities. (4) The machining status monitoring system based on new detection technologies increases the stability and safety of the machining process, placing higher demands on the sensitivity, instantaneous response, and reliability of the monitoring system. This necessitates the adoption of new detection methods, such as lightweight, small-sized, and highly sensitive new sensors (e.g., Z-elements) and the development of ultra-high-speed cutting monitoring systems with multiple detection functions. VIII. Development of Ultra-High-Speed ​​Machine Tool Technology in China China has conducted some research in the field of ultra-high-speed machine tool technology, but compared with advanced foreign technologies, there is still a significant gap that urgently needs development. Clearly, cutting tools, CNC machine tools, and machining centers are all key components of ultra-high-speed machining. The key research and development should focus on the following: (1) Research on high-power and ultra-high-speed spindle unit technology, including the built-in high-speed and high-power spindle motor and its vector control speed regulation and monitoring system, spindle material and structure (with HSK63 tapered hole), high-speed precision ceramic rolling bearing, and liquid hydrostatic hybrid bearing design and development; research on the dynamic and thermal characteristics of the spindle system, research on the elastic support technology of flexible spindle and its bearings; automatic balancing device of spindle unit; research on lubrication and cooling technology of spindle system; research on multi-objective optimization and virtual design technology of spindle; research on spindle tool changing technology to enable the spindle to reach a maximum speed of 10000 r/min to 30000 r/min. (2) Ultra-high-speed feed unit technology, including research on high-speed linear feed motor; development of high-speed position chip ring, research on high acceleration and deceleration control technology, high-speed precision AC servo system and motor; research on the matching relationship between system inertia and servo motor parameters; development of precision ball screw pair and large lead screw pair, etc. The rapid traverse speed of the high-speed feed system reaches 40 m/min to 80 m/min. n. Cutting feed speed reaches 94~60m/min, and acceleration and deceleration are greater than 1g. (3) Development of ultra-high speed machining testing technology for monitoring the functional components and drive control systems of ultra-high speed machining spindle unit, feed unit system and machine tool support and auxiliary unit system. Ultra-high speed feed unit technology. Ultra-high speed cutting tool grinding, breakage, grinding tool dressing and other status monitoring system and tool management system software to ensure rapid response replacement, intelligent tool wear and breakage monitoring system. Online monitoring technology for workpiece machining accuracy, machining surface quality and safety status in ultra-high speed cutting process. (4) HSK tool taper and tool system for high-speed and high-precision end face positioning of ultra-high speed tools, including high-speed ATC automatic tool changer, robot tool changer, and tool one-cut up to 15s. Ultra-high speed cutting tool geometric parameters and structural design, including the optimized selection of tool geometric angles, tool body safety structure, insert clamping structure, dynamic balance of rotary tools and its safety technology (rotary inserts should not break at twice the maximum speed). Develop new cutting tools and grinding materials for ultra-high-speed machining, so that the cutting speed of the tools can reach the level of developed countries in the late 1990s, and the grinding speed of the grinding wheel can reach 100m/s to 150m/s. (5) High-speed CNC system technology includes intelligent control of smooth addition and subtraction characteristics, error compensation, and feedforward control. In short, how to focus on the above-mentioned areas, concentrate limited funds, and work together to overcome difficulties and avoid low-level duplication of projects is of great significance to the revitalization and long-term development of my country's machine tool industry. [b][align=center]For details, please click: New Developments in Ultra-High-Speed ​​Machining Machine Tools and Cutting Tool Technology[/align][/b]