Grinding ratio

Equivalent to the grinding ratio G, the dressing ratio Gd is the ratio between dressed grinding wheel volume Vsd and dresser wear volume Vd, which is used to characterize the efficiency of the dressing process ... 

Cubic boron nitride (CBN) has superior thermochemical stability compared to diamond. Ultrafine-crystalline CBN (CBN-U) is a special type of CBN, which has a grinding ratio that is eight times higher, and a higher wear resistance than conventional CBN (Chen et al. 2002). For grinding of ferrous components and other materials that react with diamond, cubic boron nitride is the best choice. 

Comparison of grinding ratio between cast iron-bonded diamond (CIB-D) wheel and resinoid wheel. 

The next series of experiments were performed using diamond grinding wheels with a range of abrasive friability. Diamond grinding wheels with MBG 660, RVG, and MBG 600 diamonds were employed. RVG diamond is the most friable and MBG 660 the least friable. The bond material for all the wheels was steel. The grinding ratio for all these wheels and the cast iron powder-bonded wheels was determined for ELID grinding and for conventional grinding. The results are presented in Table 5.1. 

It can be seen that the wear rate of the grinding wheel covered with oxide film is very large, about 10 mm /mm. However, the grinding ratio value for the wheel with oxide film is larger than that of the wheel without oxide film. It can be concluded that ELID-grinding is an efficient technique whenever high productivity is required. 

The highest G-ratios are obtained when grinding with straight oil coolants. Such oils reduce power, increase maximum depth of cut, and produce smoother finishes. Disadvantages include inabiUty to remove heat from the work, oil mist in the work area, fire hazard, and tendency to hold grinding swarf (fine metal chips and abrasive particles produced in the grinding process) in suspension. Reference 51 is an excellent survey article for grinding fluids. 

Sodium sihcate (41°Bh, 1 3.22 ratio Na20 Si02) is added in the milling operation to disperse the slime, mosdy kaolin. Dispersion also aids the grinding process. The rod mill serves to grind the ore to 0.833 mm (—20 mesh) or to the point where mica, quart2, feldspar, and iron minerals are Hberated. Cyclones, or rake, hydrauhc, or other types of classifiers, are used after grinding to produce coarse and fine mica fractions that are treated separately. 

Excess NaOH is used to start the reaction and not over 35% of the chromium is added as dichromate. At the end of the reaction, the thiosulfate is removed by filtration and recovered. The hydrous oxide slurry is then acidified to pH 3—4 and washed free of sodium salts. On calcination at 1200—1300°C, a fluffy pigment oxide is obtained, which may be densifted and strengthened by grinding. The shade can be varied by changes in the chromate dichromate ratio, and by additives. 

The amount of material in a mill can be expressed conveniently as the ratio of its volume to that of the voids in the ball load. This is known as the material-to-void ratio. If the solid material and its suspending medium (water, air, etc.) just fill the ball voids, the ratio is 1, for example. Grinding-media loads vary from 20 to 50 percent in practice, and ratios are usually near 1. 

Performance The grinding-media diameter should preferably be 10 times that of the feed and should not exceed 100 times the feed diameter. To obtain improved efficiency when reducing size by several orders of magnitude, several stages should be used with different media diameters. As fine grinding proceeds, rheological factors alter the charge ratio, and power requirements may increase. 

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