Vitrified bond bonded wheel

Factorial experiments of DSG of alumina ceramics with diamond were carried out in the experimental conditions listed in Table 12.1. Before each experiment, the wheels were dressed to a completely restored cutting ability according to the bond type the vitrified bond wheel was dressed mechanically with silicon carbide superfine dressing sticks, whereas the metal bond wheel was predressed using an electrolytic in-process dressing (ELID) technique. 

Wheel Grinding. Selection of wheel, wheel speed, and fluid is important. For hard wheel grinding, vitrified bonded wheels are the most effective. Aluminum oxide (AI2O3) wheels give good results when limited to grinding speeds of 10 m/s (2000 sfin) or less. Silicon carbide (SiC) wheels can be used at 20 to 30 m/s (4000 to... 

Dressing of diamond wheels with diamond dressing tools is stiU limited. A more common method is the use of vitrified bonded silicon carbide rollers either on brake-controlled truing devices or on driven truing spindles (Wegener et al. 2011). During this dressing procedure,... 

ELID grinding is more stable than conventional grinding from the removal rate value viewpoint. Material removal rates of 250 mm /min up to 8000 mm /min were reported. The chip thickness is of an order of 1-10 nm. Stock removal rate increases with the increase in the number of passes, stiffness of machine tool, and larger grit sizes of the wheels. Cast-iron-bonded wheels have a larger stock removal rate yet a lower grinding force as compared to a vitrified bonded grinding wheel. 

Resin bonded wheels are capable of higher speeds (Fup to about 16,000 fpm) than vitrified wheels (F up to about 85,000 fpm). This is because even though a resin bonding material has lower strength, it has greater ductility and an ability to relieve points of local stress concentration by plastic flow. 

Modem civilization would not be possible without bonded abrasive products. By the year 1825 sand, emeiy, and even diamond were being bonded together with shellac for use in abrasive sticks and wheels. Rubber bonded wheels were introduced in 1857, the sodium silicate and the vitrified bond just after the Civil War, and the phenolic resin bond in 1923. The metal bond was introduced for diamond wheels in 1940. 

Vitrified bonds are very widely used in the metalworking industry, especially for machinery manufacture. The basis for this glass type bond is a fusible clay, feldspar. Refractory materials and fluxing agents are added to produce the desired composition. The dried clay and other bond ingredients are pulverized, screened, and blended to form the dry bond. This is added to the water wetted abrasive in a mixer to coat each abrasive particle with the bonding medium. The resulting mix is pressed cold in compression molds to form the basic wheel shape. 

Figure 4.13 Vitrified bonded abrasive wheels. (Copyright Saint Gobain.)...

C. Finish required influences selection of bond waA grain size. Generally speaking a resin-bonded or rubber-bonded wheel gives a better surface finish but not as good dimensional accuracy as a vitrified wheel. 

There are two main types of bonding agent inorganic and organic. Inorganic bonds are mainly vitrified, i.e. the wheel is generally fired in a furnace. Organic bonds are not fired, but are cirred at a low temperature, commonly resinoid and rubber. 

This type of bond is designated by the letter V. Vitrified wheels are porous, strong, and unaffected by water, oils and ordinary temperature conditions. In general, surface speeds do not exceed 1950 m/min. 

Vitrified Wheel. An abrasive wheel made from a batch consisting of abrasive grains and a ceramic bond formed by kiln firing at 1200-1300°C. Over half the abrasive wheels currently produced are of this type. 

Extensive ranging of abrasive wheel geometries, abrasive materials (aluminum oxide, emery, corundum, diamond. Cubic Boron Nitride (CBN)), grain size, hardness grading and bond types (resin, vitrified glass, rubber, metal) are available. 

Lower initial cost, compared to vitrified and metal bonded superabrasive wheels. 

D. Wheel speed affects the choice of bond. Vitrified wheels are not to be run in excess of 6500 siuface feet per minute except in very special cases. High speeds require resin or rubber bonds. 

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