What is grinding efficiency?

With the emergence of technological innovation and high-tech products, the processing precision and surface integrity requirements of parts are getting higher and higher. For example, the precision of the valve core and the valve sleeve, which are widely used in the precision of the hydraulic follower system, is often required to reach μM level. The precision of precision parts such as video heads and DVD players has been improved to 0.1 μM, and the laser gyro plane mirror The flatness error is required to be less than 0.05 μMRA "0.001 μM. Grinding as a conventional precision machining method is currently progressing in the direction of ultra-precision grinding, ultra-precision grinding and polishing. The hub of precision and ultra-precision grinding is the last step in which a layer of surface that is less than or is the final level of precision of the workpiece is removed from the surface of the workpiece. Therefore, in order to achieve precision or ultra-precision grinding, it is first necessary to reduce the amount of single-edge removal of abrasive particles, and the use of fine or ultra-fine particles of abrasive particles is the most effective way to reduce the amount of single-edge removal. The grinding tool used in Japanese mirror grinding has a particle size of 4000 to 8000#, and the uniform size of the fine powder is 1.5 μM to 4 μM. The surface roughness of the workpiece after processing can reach RA 0.003 μM to 0.005 μM. The surface of RA "1NM" can be obtained by polishing the sapphire single crystal by non-destructive ultra-precision grinding using SIO2 ultrafine powder with a particle size of 20NM and a tin polishing disc. At present, precision parts such as precision gauge blocks, optical flat crystals, and integrated circuit silicon substrates are all obtained by the above methods to obtain a high quality surface. In order to make the grinding pressure controllable on average, new technologies such as magnetic grinding, magnetic fluid super-fine grinding and elastic emission processing (EEM) have been developed in recent years.

Ultra-precision grinding is a systematic project, including the development of high-speed and high-precision grinding machine spindles, guide rails and micro-feed mechanisms, precision grinding tools and their balancing and finishing techniques, as well as purification and cooling methods for grinding environments. The precision grinding process of sprayed ceramics developed by Zhengzhou Grinding Abrasives Grinding Research Institute of China is commensurate with the foreign level and the grinding efficiency is higher than that of foreign countries. The process has achieved significant economic benefits after being used in Zhangjiakou Petroleum Machinery Plant and Wuhan Qingshan Thermal Power Plant.

Second, the development of new varieties of abrasives such as SG and ABN800

SG Abrasives was first introduced by NORTON in the United States. It is a new ceramic corundum abrasive made from submicron AL2O3 crystals synthesized by sol-gel process and sintered. Compared with ordinary fused corundum abrasive, not only the hardness is high, but also because the abrasive grain is a microcrystalline structure, it has a lot of crystallizing surface, and only the crystallites fall off under the action of external force or in the sharpening and trimming, and the sharp cutting is continuously generated. The blade has good self-sharpness and less peeling. The abrasive tool made by the blade has good wear resistance, less grinding heat, long service life and large grinding ratio (ratio of the volume of the grinding material to the volume consumed by the grinding tool). The high cutting rate and good grinding quality have been widely used in the fields of aerospace, automotive, bearings, tooling, instrumentation and other fields in the fields of fine grinding and forming grinding. At present, SG and WA (white corundum) or A (brown corundum) mixed abrasives are commonly used, of which SG accounts for 100%, 50%, 30%, 20%, 10%, etc., respectively, using SG, SG5 , SG3, SG2, SG1 are indicated. Some foreign excellent abrasive products, such as CB sapphire blue grinding wheel of Germany HERMES Abrasive Company, CSS grinding wheel developed by Austria TYROLIT Company, MSB grinding wheel produced by American CINCINNATIMILACRON Company, and new CX ceramic grinding wheel introduced by Japan NORITAKE Co., Ltd. are similar. SG abrasive microcrystalline sintered corundum products.

In the fierce market competition, in recent years, the United States NORTON company has introduced the second generation of SG abrasives - TG (TARGA) abrasive. It retains the strengths of the SG and makes a new breakthrough in the shape of the abrasive. It has a fine rod-like crystalline structure and is used for slow-feeding grinding and processing of difficult-to-machine materials such as inconel and superalloy. It is said that the material removal rate of TG abrasive is twice that of corundum and the life span is 7 times that of corundum.

The grinding machine of SG abrasive can be between corundum and CBN (cubic boron nitride) at an affordable price. It is a new abrasive product with a long-term application prospect. The new SG abrasive has also been successfully developed in China, and the seventh grinding wheel group company is already carrying out the industrial application of the abrasive.

ABN800 and ABN600 are new CBN abrasives developed by DEBEERS. The abrasive grains are all microcrystalline, and have high compressive strength and heat non-interference. Among them, ABN800 has more unique crystal characteristics. Abrasives have sharp angles regardless of size when crushed by force, so that they can always maintain sharp grinding function during use, so the grinding force generated during grinding is small, power consumption Less, good processing quality and long service life. In recent years, at the international exposition, some CBN abrasives exhibited abroad are mostly microcrystalline CBN abrasive products of ABN800 and ABN600.

Third, high efficiency grinding

High compiling and high precision are the two goals pursued by modern manufacturing technology. As we all know, grinding has an unparalleled advantage in terms of machining accuracy and surface roughness, but the material removal rate Q (the volume of the material in the production unit, MM3/S) is difficult to be compared with other cutting. contend. This is because Q is the product of the uniform area of ​​the wear debris, the uniform length of the wear debris, and the number of abrasive grains per unit time (the number of wear debris). Therefore, in order to improve the grinding efficiency, it is necessary to increase the number of abrasive grains per unit time (such as high-speed grinding, ultra-high-speed grinding, abrasive belt grinding, etc.), and increase the uniform area of ​​the wear debris (such as various weights). Grinding) and increasing the uniform length of grinding debris (such as slow-feeding deep grinding, vertical shaft flat grinding) and many other high-efficiency grinding techniques. The development of heavy-duty roughing, ultra-high-speed grinding, abrasive belt grinding and high-efficiency deep grinding technology is particularly striking.

The development of heavy grinding makes grinding not only suitable for precision machining and ultra-precision machining, but also for roughing and rough processing.

High-speed grinding refers to grinding with a grinding speed VC of 50M/S to 150M/S, while grinding with VC” 150M/S is called ultra-high speed grinding. In recent years, research shows that ultra-high-speed grinding not only can greatly improve the work efficiency, extend the life of the abrasive tool to reduce the surface roughness, but also can achieve ductile grinding of hard and brittle materials, and also good grinding of high plastic materials and hard-to-grind materials. Cutting effect. In the past, due to the limitation of the rotational rupture speed of the grinding tool, as well as the high grinding temperature and the surface burn of the workpiece, the grinding speed has been stagnant at around 80 M/S for a long time. Following the in-depth study of the use of CBN abrasives and the mechanism of high-speed grinding, the practical grinding speed in the industry has reached 150M/S to 250M/S, and 500M/S in the laboratory. Ultra-high-speed grinding requires ultra-high-speed grinding tools, ultra-high-speed grinding machines, grinding fluids and their liquid supply filtration systems, as well as support for grinding process monitoring and other related technologies. The high-speed grinding machine exhibited at IMTS98, TOYOTAMACHINERYUSA, grinding the drive shaft of 50HRC hardened steel, the linear speed of the grinding wheel is 120M/S; the cam grinding machine exhibited, the linear speed of the grinding wheel is 200M/S. Under the auspices of the National Natural Science Foundation of China, China has built a 200M/S ultra-high-speed grinding test rig and conducted a systematic study on the mechanism of ultra-high-speed grinding.

The processing efficiency of abrasive belt grinding is 5 to 10 times higher than that of ordinary grinding. Because it belongs to elastic grinding, it is helpful to solve problems such as grinding burns and work deformation. Therefore, abrasive belt grinding in industrialized countries has accounted for about half of the total grinding. In recent years, foreign belts have replaced ordinary corundum abrasives with CUBITRON (American 3M) ​​and SG abrasives, and the belt life has been extended due to the use of new substrates and new binders.

Slow-feeding Deep-grinding is a high-efficiency grinding technology with large depth of cut and slow-feeding. It is not only highly efficient, but also has high grinding precision and good surface quality. In particular, in recent years, a high-efficiency deep set of ultra-high speed (150M/S ~ 250M / S), large depth of cut (0.1MM ~ 30MM), fast feed (0.5M / MIN ~ 10M / MIN) HEDG (HIGHEFFICIENCYDEEPGRINDING) new technology, combined with CBN grinding wheel and CNC technology, can make the material removal rate on the unit width grinding wheel up to 2000MM3/MM·S～3000MM3/MM·S. When the forming surface and the grooved parts (such as the rotor groove and the spiral groove on the drill bit) are ground by this method, the material removal rate much higher than the cutting process can be obtained. Northeastern University of China has produced a high-power ultra-efficient deep-grinding grinding machine with a grinding machine with a power of 55 kW and a grinding speed of 250 M/S.

Fourth, the new development of superhard abrasive grinding technology

Abrasives made of diamond or CBN abrasives are called superabrasives. Because of its excellent grinding function, it has been widely used in all aspects of grinding technology, and has become ultra-precision grinding, high-efficiency grinding, difficult-to-machine material grinding, high-precision forming grinding, grinding automation and unmanned The basis for technical improvements.

Due to their complementarity in the processing materials, diamonds and CBN abrasives greatly expand the range of abrasives that can be formed by them, covering almost all of the materials including high hardness, high brittleness and high toughness. material.

Diamond grinding tools are the best abrasive tools for grinding hard and brittle materials such as cemented carbide, optical glass, ceramics and adjective stone, but they are not suitable for grinding steel materials and super because they are easily carbonized at 700 °C ~ 800 °C. High speed grinding. The rise of CBN abrasives has revolutionized the grinding technology. It can withstand the high temperature of 1300 ° C ~ 1400 ° C, chemical inertness to iron elements, good thermal conductivity, high resection rate when grinding steel, grinding ratio, grinding With long life, it is the best abrasive for grinding high hardness and toughness metals such as hardened steel, high speed steel, high strength steel, stainless steel and heat resistant alloy. In addition, CBN grinding tools are also used for ultra-high speed grinding, and the metal matrix CBN abrasives will not break when the line speed exceeds 250M/S.

The extensive use of CBN grinding tools is mainly due to the advent of various high-efficiency and high-performance CNC grinding machines in recent years, as well as the improvement of abrasive manufacturing technology. New abrasive tools such as single-layer plating and high-temperature brazing, which have excellent functions, have been developed, which have promoted grinding. The development of technology, especially the efficient grinding of new processes is more popular.

QUICKPOINTGRINDING was first introduced by the German company JUNKER. It is realized by brazed CBN thin grinding wheel (width only a few MM) and ultra high grinding wheel linear speed (120M/S ~ 180M / S, high up to 200M / S ~ 250M / S). During machining, the axis of the grinding wheel and the axis of the workpiece form a certain inclination angle in the horizontal direction, so that the theoretical line contact between the grinding wheel and the workpiece becomes point contact. This can greatly reduce the area of ​​the grinding contact area, and the extremely high grinding speed can make the grinding chips thinner, the abrasive load is reduced, and the heat can not be transmitted to the workpiece and the grinding wheel, which is almost taken away by the grinding debris. Improve workpiece machining accuracy and surface quality. The use shows that the grinding rate of point grinding is large, the grinding wheel has a long service life, the dressing frequency is low, the material removal rate is high, and because it uses the same two-coordinate linkage with the NC lathe to achieve surface grinding of complex rotary parts, one installation It can process all shapes such as outer circle, cone surface, curved surface, thread, shoulder and groove. It has more flexibility than cutting and grinding, and the cooling effect is excellent. The grinding temperature is low, and even dry grinding can be realized. The process has been used in the production line of the Santana car of Shanghai Volkswagen Automotive Co., Ltd. in China, and has achieved obvious economic benefits.

Fifth, the development direction of grinding technology

Grinding In addition to the development of ultra-precision, high-efficiency and super-hard abrasives, automation is also one of the important directions in the development of grinding technology. At present, based on the maturity and popularity of CNC technology, grinding automation is further developing towards numerical control and intelligence. Many special grinding NC software and systems have been commercialized. Grinding is a complex multivariate impact process. The intelligent processing and resolution planning of its information is an important basis for flexible automation and optimization. At present, the main applications of artificial intelligence in grinding include grinding process modeling, rough selection of grinding tools and grinding parameters, monitoring and monitoring of grinding process monitoring, adaptive control optimization, intelligent process design and intelligent process library. In recent years, the grinding process modeling, simulation and simulation techniques have been greatly developed and have reached a practical level.

In China, there are many achievements in the modeling and simulation of grinding process, monitoring and identification of acoustic emission process, surface burn and residual stress prediction, on-line detection, evaluation and compensation of grinding machining error, and a new type of parallel grinding has been developed. Cut the robot.

Although the production of artificial abrasives in China started late, it has developed rapidly and has a commensurate share in the world.

It must be pointed out that in recent years, foreign grinding technology has developed rapidly, such as the research on the grinding mechanism and process of hard and brittle materials, the use of dry grinding heat to heat the workpiece at the same time, and the non-polluting grinding without grinding fluid. All of us have.

Concerned about surprises

Label: Grinding efficiency

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