1.TYPE OF DIAMOND ABRASIVE
The diamonds used for grinding ceramics are mainly synthetic diamonds. The synthesis process permits control of diamond characteristics generating either blocky grit shapes with high
impact strength, or friable grits with low-impact strength. Diamonds are classified by grit size and grit size distribution. The grit system can be used for getting desired working result within
a wide range.
2. BONDS OF DIAMOND WHEEL
Grinding wheel have three components: abrasive, bond, and core. In general application, diamond wheels can be resin, metal, or vitrified bond wheels classified by the bond material.
Resin bonds have been widely used for diamond wheels and offer the particular feature of structural flexibility. Phenolic resins and their derivatives are still the most commonly used bond types. Resin-bonded wheels are easy to use in a wide range of applications.
When machining ceramic materials, it is important to minimize external vibration sources because of the brittle nature. The grinding wheel must be prepared and conditioned to reduce run-out error, clamping error, and grinding wheel unbalance. Keeping the weight of the grinding wheel low helps to minimize vibrations.
3. WHEEL TRUING AND DRESSING
Dressing is the process of conditioning of the wheel surface so as to achieve a certain grinding behavior.
Generally dressing is the process of conditioning worn grains on the surface of a grinding wheel in order to produce sharp new grains and truing out-of-round wheels. Dressing is necessary when excessive attritious wear dulls the wheel or when the wheel becomes loaded. Dulling of the wheel is known as glazing because of the shiny appearance of the wheel surface. Loading occurs when the pores on the surface of the wheel become filled or clogged with chips. Pre-grinding preparation of superabrasive wheels usually involves two distinct processes: truing and dressing. One popular truing method for diamond wheels utilizes a vitrified green (friable) silicon carbide grinding wheel mounted on a brake-controlled truing device. The truing wheel is operated as if it cylindrically traverse grinds the grinding wheel. The axes of the dressing wheel and grinding wheel are parallel to each other.
After truing, dressing of superabrasive wheels is usually accomplished by in-feeding a fine grained vitrified abrasive stick into the wheel surface.
4.PHYSICS OF GRINDING CERAMICS
The material-removal rates vary depending on the application.
With recent advances toward understanding of the mechanics, it is possible to achieve more material-removal rates comparable to that in metal grinding.
Ceramic materials are more brittle than metallic materials and show very little plastic deformation under load up to the point of fracture. Then it might be expected that the mechanism of abrasive machining of ceramic materials would mainly involve brittle fracture.