Ultra-high-speed grinding is an important part of advanced manufacturing methods, and is the main processing method for various processed materials to obtain precise dimensions and surface integrity. Discussed the related technology of ultra-high-speed grinding, analyzed the domestic and foreign current situation, latest developments and specific applications of ultra-high-speed cylindrical grinding, fast-point grinding and high-efficiency deep-cutting grinding. The importance of the development of ultra-high-speed grinding processing.

The applications of ultra-high-speed grinding include high-efficiency deep-cut grinding (HighEf-ficiencyDeepGrinding, HEDG), ultra-high-speed cylindrical grinding, ultra-high-speed precision grinding, quick-point grinding (Quick-point Grinding), hard and brittle materials and difficult-to-process Material ultra-high speed grinding, etc.

1.1 Efficient deep-cut grinding

High-efficiency deep grinding technology is developed in recent years, which integrates high speed (100 ~ 250 m/s), high feed speed (0.5 ~ 10 m/min) and large cutting depth (0.1 ~ 30 mm) of the grinding wheel. Efficient grinding technology. The concept of efficient deep grinding was founded in 1980 by Professor Werner of Bremen University in Germany. At present, European companies occupy a leading position in the application of high-efficiency deep grinding technology. Efficient deep grinding can be viewed intuitively as a combination of slow-feed grinding and ultra-high-speed grinding. Different from ordinary grinding, high-efficiency deep grinding can complete the rough and fine machining process consisting of multiple processes such as turning, milling, and grinding through a grinding stroke, and obtain a metal removal rate much higher than that of ordinary grinding (metal The removal rate is 100 to 1,000 times higher than that of ordinary grinding), and the surface quality can also reach the level of ordinary grinding. The high-efficiency deep-cutting grinding process begins with the use of a resin-bonded alumina grinding wheel at a speed of 80-100 m/s to deep-grind the drill bit’s spiral groove. Because it uses a much faster feed rate than the slow feed grinding, the production efficiency is greatly improved. Later, on the basis of CBN grinding wheel, the ultra-high-speed deep grinding machine with 200 ~ 300 m/s was further developed. The FD613 ultra-high-speed surface grinder from GuhringAutomation, Germany, uses a CBN grinding wheel to grind rotor slots with a width of 1-10 mm and a depth of 30 mm at 150 m/s. The table feed speed reaches 3,000 mm/min. On a 125 m/s groove grinder, the 20 mm deep drill groove can be ground in one go, and the metal removal rate reaches 500 mm3/(mm·s). High-efficiency form grinding is also widely used as a kind of high-efficiency deep grinding, and can be used to complete the processing of more complex and heterogeneous surfaces with the help of a CNC system. This technology has been successfully applied to lead screws, screws, gears, rotor grooves, tool grooves, etc. to replace milling. The comparison of the process parameters of ordinary grinding, slow feed grinding, and high-efficiency deep-cutting grinding methods is shown in Table 1. Japan’s Toyota Koki, Mitsubishi Heavy Industries and other companies are able to produce CBN ultra-high-speed grinders, and Mitsubishi Heavy Industries’ CA32-U50ACNC ultra-high-speed grinders with ceramic bond grinding wheel speeds can reach 200 m/s. The GP-33 ultra-high-speed grinder adopts CBN grinding wheel to realize automatic grinding of different parts of the workpiece at a grinding speed of 120 m/s. EdgetrkMachine in the United States also produces high-efficiency deep-grinding machine tools. The company mainly develops small 3-axis, 4-axis and 5-axis CNC high-efficiency deep-grinding machine tools. It uses CBN shaped grinding wheels to achieve efficient deep-grinding of hardened steel, and the surface quality is comparable to ordinary Grinding is comparable. Efficient deep-cutting grinding has the characteristics of short processing time (usually 0.1 to 10 s), high grinding force, and high grinding speed. In addition to the technical requirements for ultra-high-speed grinding, it also requires the machine tool to have high rigidity. Generally, HEDG requires that the driving power of the machine tool spindle is 3 to 6 times larger than that of creep feed grinding. For example, a 400 mm grinding wheel requires at least 50kW of power.

1.2 Ultra-high-speed cylindrical grinding

Increasing the speed of the grinding wheel can help reduce the surface roughness of the grinding, and can achieve high-efficiency ultra-high-speed precision grinding. Ultra-high-speed cylindrical grinding uses a grinding wheel peripheral speed of 150 m/s or more and a CBN grinding wheel, equipped with a high-performance CNC system and a high-precision micro-feed mechanism, to perform ultra-high-speed precision grinding of the outer rotary surface of the spindle, crankshaft, etc. The method of cutting. It can not only ensure high processing accuracy, but also obtain high processing efficiency. This technology has been successfully applied to the automotive industry in Japan. For example, using the GCH63B CNC ultra-high-speed cylindrical grinder of Toyota Machinery Co., Ltd. to grind ductile iron camshafts with a machining allowance of 5 mm, the metal removal rate can reach 174 mm3 / (mm s), and the grinding wheel grinding ratio Up to 33 500. With the surface roughness Ra = 3 μm as the upper limit, the grinding wheel can continuously grind 60 workpieces after one dressing, and the surface after grinding shows residual compressive stress, and it can be directly ground from the blank to the finished product, eliminating the need for turning processes and turnover between processes . Toyota Koki’s GZ0 CNC ultra-high-speed cylindrical grinder is equipped with ToyodaState Bearings. It uses a 200 m/s thin CBN grinding wheel to perform longitudinal trajectory grinding of the rotating parts at one time to complete the flexible processing of the entire workpiece. These are of great significance to production management and cost reduction. On the RB625 ultra-high-speed cylindrical grinder of Guhring Automation in Germany, the CBN grinding wheel can also be used to grind the blank into a spindle at one time, which can remove 2 kg of metal per minute. Ultra-high-speed precision grinding uses ultra-high-speed precision grinders, and through precision trimming of micro-abrasives, the sub-micron depth of cut is used to obtain sub-micron-level precision in a clean processing environment.

1.3 Quick point grinding

Quick-point Grinding (Quick-point Grinding) is an advanced ultra-high-speed grinding technology developed and patented by Mr. Erwin Junker, Junker, Germany in 1994. It integrates the three advanced technologies of ultra-high-speed grinding, CBN super-hard abrasive and CNC flexible processing, and has excellent processing performance. It is another high-speed grinding technology in terms of high efficiency, high flexibility, and high-quality stability in mass production. A new development. This process is mainly used for the processing of shaft and disc parts. The axis of the CBN or synthetic diamond superabrasive grinding wheel forms a certain inclination angle with the axis of the workpiece in the horizontal and vertical directions, and the thin grinding wheel is used to form a small area point contact with the workpiece, and the continuous trajectory numerical control technology is comprehensively used to grind at an ultra-high speed. Grinding process. It not only has the versatility and high flexibility of CNC turning, but also has higher efficiency and precision, long life of the grinding wheel, and very stable quality. It is an excellent combination of a new generation of CNC turning and ultra-high-speed grinding, and it has become a super-high-speed grinding. One of the main technical forms. Germany is currently in a leading position in the research and development of this new technology. At present, it has been applied in the foreign automobile industry and tool manufacturing industry, especially in the field of automobile parts processing, namely gear shafts or camshafts. Most of these parts include cutting, journals, shoulders, eccentricity and thread grinding processes. The application of this process can achieve all machining through one clamping, which greatly improves the machining accuracy and productivity of the parts. The grinding process of rapid point grinding is different from ultra-high-speed grinding in the general sense. Its technical characteristics are as follows: (1) Rapid point grinding is controlled by the numerical control system to control the axis of the grinding wheel in the vertical direction and the axis of the workpiece at an angle of ±0.5° (Picture 1), in the horizontal direction according to the characteristics of the workpiece line, it can vary from 0 to 30° to minimize the contact area of ​​the grinding wheel/workpiece and avoid interference between the end face of the grinding wheel and the shoulder of the workpiece. The dynamic balance of the grinding wheel can be automatically completed on the machine, and the radial runout accuracy is within 0.002 mm. (2) Fast point grinding adopts ultra-hard abrasive thin grinding wheels with a thickness of 4 to 6 mm, and adopts a three-point positioning installation system for quick installation, high repeat positioning accuracy, and can solve the problem of hole expansion caused by centrifugal force. (3) In order to obtain a high metal removal rate and prevent the grinding wheel from generating excessive centrifugal force, the workpiece is also rotated at a high speed (up to 12 000 r/min). The actual grinding speed is the superposition of the speed of the grinding wheel and the workpiece. 200 ~ 250 m/s. (4) When grinding the outer circle, the material removal is mainly completed by the side of the grinding wheel, and the periphery only plays the role of smooth grinding. Therefore, the circumferential wear of the grinding wheel is extremely slow, the service life is long (up to 1 year), the grinding ratio can reach 16 000 ~ 60 000, a “quick point grinding” grinding wheel can grind several tons of steel, and the grinding wheel dressing rate is low ( Each trimming can process 2×104 parts), and the production efficiency is 6 times higher than that of ordinary grinding. (5) Equipped with a two-axis numerical control diamond roller dresser, when the width of the grinding wheel wears more than 10%, it can automatically and accurately dress to avoid premature dressing to control costs. (6) The contact area between the grinding wheel and the workpiece is small, the grinding force is greatly reduced, and the grinding heat is less. At the same time, the grinding wheel is thin and the cooling effect is good, so the grinding temperature is greatly reduced, and even “cold state” processing can be realized, which improves the processing accuracy And surface quality. (7) Since the grinding force is extremely small, the workpiece can be easily clamped by the friction of the center, which is called “top grinding” and “skin grinding”. (8) Due to the use of CNC to achieve complex surface grinding, all contours such as outer circle, tapered surface, curved surface, thread, shoulder and groove can be completed after one installation. It can also combine the turning and grinding processes to further improve processing efficiency. (9) Use high-speed grinding oil injection for cooling. Because the high-speed rotating grinding wheel throws the grinding oil into oil mist, the processing must be carried out automatically in a closed environment, and it must be equipped with a suction and exhaust system and a high-efficiency wear debris separation and oil-gas separation unit. Grind the main shaft with the fast point grinding method, and complete the grinding of the outer circle, the shoulder, the groove and the fastening thread in one clamping; the camshaft can be ground, and the journal and thrust shoulder can be completed in one clamping All three parts of the outer diameter of the end and the end are ground, and the dimensional accuracy reaches IT6, Ra≤0.8 μm. Compared with the traditional process, the cost is greatly saved.

1.4 Ultra-high speed grinding of hard and brittle materials and hard machining materials

With the development of modern high science and technology and industrialization, hard and brittle materials such as engineering ceramics, functional ceramics, monocrystalline silicon, red sapphire and optical glass have been widely used. Grinding hard and brittle materials with super hard abrasive at high speed or super high speed has become almost the only machining method. Under normal grinding conditions, the grinding particles are immersed deeply into the workpiece, and the grinding chips are mainly in the form of brittle fracture. However, the number of grinding particles per unit time in ultra-high speed grinding increases greatly. The cutting thickness of a single grinding particle is extremely thin, making it easy for hard and brittle materials such as ceramics and glass to produce grinding chips in the form of plastic deformation, which greatly improves the surface quality and efficiency of grinding. So ultra-high speed grinding can realize ductile grinding of hard and brittle materials. For example, when using diamond grinding wheel to grind silicon nitride ceramics at the grinding speed of 160 m/s, the grinding efficiency is doubled compared with 80 m/s, and the grinding life of the wheel is 1.56 times and 7 times that of 80 m/s and 30 m/s, and good surface quality can be obtained. Nickel-based heat resistant alloy, titanium alloy, high temperature alloy, high strength alloy steel and other refractory materials have extremely poor grinding performance under ordinary grinding conditions. Grinding wheel passivates quickly, grinding temperature is high, surface quality is poor. Under ultra-high speed grinding condition, the chip deformation velocity is close to the static plastic deformation stress wave propagation velocity, the material deformation strain rate is very high, the plastic deformation hysteresis, which is equivalent to the plastic reduction of the material, reducing the processing hardening tendency, surface roughness and residual stress, so as to realize the “brittleness” processing of ductile materials. For example, when grinding pure aluminum with 200 m/s, the surface hardness of the workpiece is 50 HV, and the surface roughness Ra is 2.2 m. When the grinding speed is 280 m/s, the surface hardness of the workpiece is 45 HV and Ra is 1.8 m. It can be seen that when the grinding speed is greater than 200 m/s(the static stress wave propagation velocity of pure aluminum is about 200 m/s), the value of work hardening and surface roughness decreases and the surface quality improves. Therefore, in the ultra-high speed grinding condition, hard, brittle, high toughness, high plastic materials can also obtain good grinding performance. In the theme report of grinding committee of the 42nd annual meeting of the International Society for Production Engineering Research, it was clearly pointed out that the high performance machining of heat-resistant alloy and aluminum alloy refractory materials should be an important application field of ultra-high speed grinding technology.

High speed and ultra-high speed grinding is an important part of advanced manufacturing method, which can greatly improve production efficiency and machining quality and reduce cost. The high speed grinding technology is paid more attention to by the industrial developed countries in the world and has begun to enter the practical stage. There is a big gap between China and foreign countries in the research and utilization of ultra-high speed grinding technology. It is of great significance to strengthen the research, popularization and application of ultra-high speed grinding technology to improve the processing level of China’s machinery manufacturing industry and accelerate the development of new products. With the further maturity of the basic theory of ultra-high speed grinding and the technology of key components, ultra-high speed grinding will play a more and more important role in industrial production and has a good development potential.