1, choose the appropriate wheel

Different workpiece materials, different processing requirements, should use a different wheel. Even if the same kind of grinding the workpiece material, different brands of wheel grinding ratio can vary from 2 to 5 times, so you want to choose the right wheel.

Diamond Wheel is the best abrasive grinding carbide, optical glass, ceramics, gem stone high hardness and brittleness of non-metallic materials. But the diamond at 700 ℃ ~ 800 ℃ when easy carbonation, so it is not suitable for grinding steel material. CBN is slightly inferior to the hardness of diamond, but it is a good thermal stability (capability 1300 ℃ ~ 1400 ℃ high temperature), it does not like the diamond that will break down at high temperatures, namely oxidation and graphitization, and iron group elements chemically inert big, high thermal conductivity (corundum 46 times), with a long (up to corundum grinding wheel several times to hundreds of times over) wheel life of its production, is an alternative to alumina grinding of hardened steel, high speed tool steel, bearing steel best abrasive stainless steel, heat-resistant steel and titanium alloys, high hardness and toughness large metal materials.

Grinding wheel binder resin, metal, ceramic, plating and brazing. Resin bonded grinding wheel is mainly used for measuring blade sharpening, grinding bore, cylindrical grinding and surface grinding; metal bonded grinding wheel for cutting, grinding optical curve grinder shaped, single-point tool sharpening, grinding small drill spiral groove, also applies to the electrolytic grinding; grinding efficiency vitrified grinding wheels, good shape retention, high durability, easy dressing, long wheel life, and because of vitrified itself has good chemical stability, heat, oil, acid erosion, can be adapted to a variety of grinding fluids, grinding low-cost, efficient and thus has become the preferred abrasive precision grinding; plating and grinding wheel suitable for high speed forming mill, also suitable hole efficient grinding (wet milling) and used on jig grinders; brazed grinding wheel suitable for ultra-high speed.

It must be noted, different grades of abrasive, because the manufacturing process is different, the crystal morphology, particle shape are different, have different strength, thermal stability and broken characteristics, should be based on the type of binding agent, grinding and grinding the workpiece material way, select a different abrasives. Such as for efficient, high-precision grinding vitrified grindstone, the choice of high strength and sharp abrasive particle shape, such as DeBeers company's PDA type (synthetic diamond varieties) and ABN800 type (CBN varieties) or other similar properties grades.

Superhard grinding capacity but also metallised surface coating (metal coating can play a toughening reinforcement, thermal shock and slow down play the role of bridge between the combination of grains and binder, can increase the grinding wheel performance) and two non-metallized coating species should be selected depending on the conditions binding agent type, workpiece material, dry and wet and so on. Dry grinding is generally used copper clothing, such as RVD-Cu, CBN-Cu; wet grinding of nickel selection of clothing, such as RVD-Ni, CBN-Ni current, metal plating by nickel, copper development to titanium, tungsten alloys, non-metallic. ceramics, etc., by the development of a single coating composite coating, and has been developed to a fine powder abrasive plated plated.

From the concentration of hard abrasive wheel can not be selected too low, high concentrations can bring a high grinding ratio, 200% concentration of superabrasive grinding wheel is actually a kind of super abrasive ordinary wheel as accessories, is generally not recommended naming use. Currently, high-speed and efficient grinding higher concentrations are used, vitrified CBN grinding wheel are made of high density and efficient concentration, the concentration of CBN grinding wheel generally choose more than 125%, such as supporting the import of ceramic CBN grinding wheel, its concentrations generally are 175% to 200%.

Wheel hardness level indicates a binding agent for the abrasive gripping force size. Wheel hardness uniformity and stability and hardness level of rational choice, is an important prerequisite to ensure the quality of the grinding. Foreign grinding wheel generally have three to seven hardness levels to choose from, but China's production of super-hard grinding wheel is not standard hardness grade, GB6409 also does not provide for appropriate standards, it is difficult to guarantee quality, inconvenience to the user, urgently supplement and perfect.

2. Select the appropriate amount of grinding

Super abrasive grinding wheel speed should be selected according to the specific conditions of the type of grinding wheel, grinding mode and cooling. Improve the speed of the grinding wheel, can significantly improve the efficiency of grinding and grinding ratio (grinding wheel speed such as 40%, grinding ratio can be doubled), lower grinding costs. Diamond Wheel of metal and resin binder, grinding speed is usually 15 ~ 35m / s, vitrified CBN grinding wheel speed can be increased to 45 ~ 160m / s, single-CBN grinding wheel speed can choose 125 ~ 250m / s.80 ~ 125m / s line speed CBN grinding wheel has become the mainstream of current. Grinding depth is generally 0.002 ~ 0.010mm, workpiece speed is usually 10 ~ 30m / min, feed rate longitudinal desirable 0.3 ~ 1.5m / min., Whichever is greater value kibble, take a small value when grinding.

3, super-hard grinding wheel for grinding machine requirements

Superhard grinding wheel, especially high-speed grinding, processing requirements and good stability, vibration, high-speed line. For example, on CIMT2001 display PLANOMAT series flat and shaped grinding wheel working speed of 170m / s Therefore, there is a grinder requirements: (1) wheel spindle rotation accuracy is higher. (2) grinding machine rigidity is better, generally require more than 50% of normal grinding machine tall, usually not less than 100N / μm magnitude. Grinding wheel master micro letter: 2105551090 (3) grinding machines, feed accuracy of the system is higher, the feed rate should be uniform and accurate, longitudinal feed should reach a minimum speed 0.3m / min, cross feed (depth of cut) should reach 0.001 to 0.002 mm / single pass, in order to ensure dimensional precision grinding, precision geometry and surface roughness. (4) grinding machines, various moving parts, such as the headstock spindle and bearing part, the feed should be a reliable seal and other sports track sections, to prevent the super abrasive enter accelerated mechanical wear and tear. (5) have a fairly complete grinding fluid supply and filtration system, filtering accuracy should be less than 0.5μm. Each section (6) grinder should be the appropriate anti-vibration and vibration isolation measures should be fine grinding wheel balancing.

4, grinding wheel dressing

Grinding wheel dressing, shaping and sharpening usually divided into two processes. Shaping the grinding wheel cutting trace to reach the geometry and the required precision, and fine crushing abrasive tip, forming a micro blade; dressing is to remove the binding agent between the grains, so that between the abrasive particles have a chip space , binding agent and abrasive grains projecting outside, forming the cutting blades.

For multi-pore vitrified grinding wheel (including diamond and CBN grinding wheel), due to the binding agent is loose type, generally shaping and sharpening can be completed; and the binding agent is a dense wheel (such as resin, metal binding agent) , the shaping and sharpening shall be carried out separately.

Grinding wheel the most effective tool for shaping the most important diamond dressing tools. With a single grain diamond dressing, since the dressing tool wear, and often affects the profile accuracy. Such as with a diamond wheel dresser, dresser avoid excessive wear and tear, and to get a better wheel topography. Trimming device feed higher precision, each feed should be controlled in the micron level. Excess trimming affects both grinding quality, will greatly reduce wheel life.

Sharpening many ways, generally using mechanical methods (such as corundum block cut dressing, dressing hydraulic injection method) or EDM method. The latter are used for grinding wheel metal binding agent, the grinding wheel as an anode by electrolysis will spark or metal bond erosion; if adding graphite powder in a binder, and this method is also suitable for resin, vitrified grindstone.

In recent years, the University of Tokyo developed a rotary cup-shaped diamond wheel dressing tools. The mechanism is the use of falling down from the cup-shaped wheel between superhard abrasive (diamond or CBN) grains and binding bridges impact between the binding agent, and falling down with the superhard abrasive abrasive grinding wheels have squeezed to achieve the purpose of dressing. With this method, both the multi-pore ceramic bonded superhard grinding wheel, or dense wheel, shaping and sharpening can be completed, but due to the cup-shaped grinding wheel from rotating, so the wear is very small, almost finishing the process of shaping forces can remain change, and the value is much less than when using a single dresser dressing diamond particles.

5, the proper use of grinding fluid

When the super abrasive grinding wheel, use a dry or wet milling. But the use of wet milling, can extend wheel life, but will also prevent the workpiece grinding burn. Different grinding fluid, will make a difference than the grinding wheel several times, even 10 times. Wheel mechanical abrasion, chemical attack and thermal injury during the grinding process is closely related to the cooling effect. But with the CBN grinding wheel wet grinding it should be noted that, due to CBN at high temperatures, together with water vapor and oxygen in the air from the reaction of ammonia and boric acid (BN + 3H2O → H3BO3 + NH3), this reaction is called hydrolysis, will accelerate wheel wear. So commonly used water-soluble oil or aqueous solutions with extreme pressure additives to weaken hydrolysis in use. Different grinding fluid wet milling, the relative life of CBN grinding wheels are different, pure oil cooled longest wheel life, water-soluble oil-cooled wheel life, followed by cooling water additives plus rust wheel life minimum.

6, grinding wheel unconventional use

Usually people think that, because diamond and iron group elements chemically inert and large, it is not suitable for grinding diamond wheel a gray cast iron workpieces. However, this situation occurs only when the high temperature. For example, when a diamond grinding wheel, when the temperature reaches 650 ℃, the diamond will be oxidized in the air, and reaches 700 ℃ ~ 800 ℃ it will graphitized. At low temperatures, the material does not occur between these reactions. So, as long as the appropriate choice of the use of wet milling and grinding speed mode, while supplying sufficient grinding liquid, diamond grinding wheel is perfectly cast, and this has been proven in production practice. When using wet grinding, diamond grinding wheel grinding than gray cast iron (9600) than gray cast iron with CBN grinding wheel grinding ratio (2700) is much higher.

It is also generally believed, CBN grinding wheel is not suitable for low-carbon steel for a class of soft material, because the wear debris generated at this time of easy to make the wheel jam. But the study suggests that, vitrified CBN grinding wheel can be taken to increase the wheel speed to form fine debris, then by high pressure liquid jet grinding remove debris, as well as an adequate supply of grinding fluid and other measures to prevent wheel loading. Thus, CBN grinding wheel is low-carbon steel (hardness greater than 30HRC) a class of soft material. However, CBN grinding wheel is not valid any material. Usually it is not suitable for grinding carbide and carbide and steel assembly, this time with a diamond grinding wheel has a better effect.

7 Conclusion

Our artificial super abrasive production, though started late, but developed rapidly in China in 1997, synthetic diamond production has reached about 500 million karats, CBN annual output of 8 million karats. Diamond Wheel Masters micro letter: 2105551090 has initially formed a super-hard abrasives, grinding fluid dedicated, specialized finishing techniques and a complete system of specialized equipment and grinders. At present, China is capable of producing RVD, CBN and metallized coating high-grade abrasive articles, such as "metal matrix ceramic CBN grinding wheel", "65m / s vitrified CBN grinding wheel" and other super abrasive grinding wheels of different specifications has formed a series, ultra hard abrasive wheel diameters up to φ750mm (under trial φ1100mm wheel), the maximum line speed of up to 80m / s, and in the development of 125m / s high-speed wheel, to promote the use of superhard abrasive grinding wheel to create the conditions. Can be expected, with the widespread use of the grinding wheel, it will promote the transformation and development of grinding machine manufacturing, and the development of efficient high-performance grinding machine, in turn further promote the use of grinding wheel.