As we all know, grinding wheel is the most important type of abrasive tool in grinding process. The grinding wheel is a porous body made by adding a binder to the abrasive, compacting, drying and firing. Due to different abrasives, bonding agents and manufacturing processes, the characteristics of grinding wheels vary greatly, which has an important impact on the processing quality, productivity and economy of grinding. The characteristics of the grinding wheel are mainly determined by factors such as abrasive, strength, bond, hardness, structure, shape and size.
According to the abrasives used, it can be divided into ordinary abrasives (corundum and silicon carbide, etc.) grinding wheels and natural abrasive superabrasives and (diamond and cubic boron nitride, etc.) grinding wheels;
According to the shape, it can be divided into flat grinding wheel, bevel grinding wheel, cylindrical grinding wheel, cup grinding wheel, dish grinding wheel and other toolroom grinding wheels; according to the bond, it can be divided into ceramic grinding wheel, resin grinding wheel, rubber grinding wheel, metal grinding wheel, etc. The characteristic parameters of the grinding wheel mainly include abrasive, viscosity, hardness, bond, shape, size, etc.
Since the grinding wheel usually works at high speed, a rotation test (to ensure that the grinding wheel will not break at the highest operating speed) and a static balance test (to prevent vibration of the machine tool during work) should be carried out before use. After the grinding wheel has been in operation for a period of time, it should be dressed to restore the grinding performance and correct geometry.
The characteristics of the grinding wheel used on the grinding machine are:
Due to the intense friction, the temperature in the grinding zone is very high. This can cause 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 also acts as chip removal and lubrication.
The radial force during grinding is very large. This will cause the elastic retreat of the machine tool-grinding wheel-workpiece system, making the actual depth of cut less than the nominal depth of cut. Therefore, when the grinding is about to be completed, smooth grinding should be carried out without entering the knife to eliminate errors. After the abrasive grains are blunted, the grinding force also increases, causing the abrasive grains to break or fall off, re-exposing the sharp edge. This feature is called self-sharpening. Self-sharpening enables normal grinding within a certain period of time. However, after a certain working time, it should be manually trimmed to avoid vibration, noise and damage to the surface quality of the workpiece caused by the increased grinding force.
Due to the high hardness and heat resistance of the grinding wheel abrasive itself, grinding can process materials with high hardness, such as hardened steel and cemented carbide. The characteristics of the grinding wheel and the grinding machine determine that the grinding process system can perform uniform micro-cutting, generally ap=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 is adopted, Therefore, grinding can economically obtain high machining accuracy (IT6~IT5) and small surface roughness (Ra=0.8~0.2m). Grinding is one of the main methods of component finishing.
