Heartless grinding wheel: Application of grinding wheel methods in stone grinding processing

       （ 1 ）Because the abrasive grains of the grinding wheel have high hardness and heat resistance, it can process materials with high hardness, such as quenched steel and cemented carbide.

       （ 2 ）The characteristics of the grinding wheel and grinding machine determine whether the grinding processing system can perform uniform micro-cutting, generally p = 0.001 〜 0.005mm ； The grinding speed is very high, generally up to v = 30 〜 50m / s ； The grinding machine has good rigidity; hydraulic transmission, so high processing accuracy (can be obtained economically IT6 〜 IT5 ）and smaller surface roughness（ Ra = 0.8 〜 0.2 μ m ）。Grinding is one of the main methods for precision machining of parts.

       （ 3 ）Due to intense friction, the temperature in the grinding area is very high. This will lead to stress and deformation of the workpiece, and even burn the surface of the workpiece. Therefore, a large amount of coolant must be injected during grinding to reduce the grinding temperature. The coolant can also play a role in chip removal and lubrication.

       （ 4 ）The radial force during grinding is very large. This will cause the machine tool grinding wheel - Workpiece system elastic recoil, so that the actual cutting depth is less than the nominal cutting depth. Therefore, when the grinding is about to be completed, smooth grinding should not be used to eliminate errors.

       （ 5 ）After the abrasive grains become blunt, the grinding force will increase, causing the abrasive grains to break or fall off, and sharp edges will be exposed again. This characteristic is called "self-sharpening". Self-sharpening can allow grinding to proceed normally for a certain period of time, but after a certain working time, manual dressing should be performed to prevent vibration, noise and damage to the surface quality of the workpiece due to the increased grinding force.

       The grinding wheel is a cutting tool used for grinding. It is a porous object made of many small hard abrasive particles and a binder. Abrasive particles are directly responsible for cutting work, and must be sharp and have high hardness, heat resistance and certain toughness. Common abrasives are aluminum oxide and silicon carbide. Aluminum oxide-based abrasives have high hardness and good toughness, suitable for grinding steel. Silicon carbide abrasives have higher hardness, sharper, better thermal conductivity, but more brittle, suitable for grinding cast iron and cemented carbide.

       Grinding wheels with the same abrasive have different surface roughness and processing efficiency after processing due to their different thicknesses. Coarse abrasives are used for coarse grinding, while fine abrasives are suitable for fine grinding. The coarser the abrasive, the smaller the particle size.

       The binder is used to bond the abrasive. Commonly used are ceramic bonds, followed by resin bonds. Different binder materials will affect the corrosion resistance, strength, heat resistance and toughness of the grinding wheel.

       The stronger the adhesion of the abrasive grains, the less likely they are to fall off the grinding wheel. The hardness of the grinding wheel is called the hardness of the grinding wheel, which refers to the difficulty of the abrasive on the surface of the grinding wheel falling off under external force. Easy to fall off is called soft, and vice versa is called hard. The hardness of the grinding wheel and the hardness of the abrasive are two different concepts. The surface of the workpiece to be ground is soft, and the cutting edge (edge) of the abrasive grain is not easy to wear, so it can be used for a long time. That is, a more solid bonded grinding wheel (higher hardness grinding wheel) can be selected. Conversely, low-hardness grinding wheels are suitable for grinding high-hardness workpieces.

       The grinding wheel works under high-speed conditions. To ensure safety, it should be inspected before installation, and there should be no defects such as cracks. In order to make the grinding wheel work smoothly, a dynamic balance test should be carried out before use.

       After the grinding wheel has been working for a period of time, the gaps on the surface will be blocked by grinding debris, the sharp corners of the abrasive will become blunt, and the original geometric shape will deform. Therefore, it must be dressed to restore cutting ability and correct geometric shape. The grinding wheel needs to be dressed with a diamond pen.