The abrasive flap disc is a grinding cutting tool and is a porous object made up of many small and hard abrasive grains and bonding agents. The abrasive particles are directly responsible for the cutting work and must be sharp and have high hardness, heat resistance and certain toughness. Commonly used abrasive flap discs are alumina flap disc(also known as corundum) and silicon carbide flap disc. Alumina abrasives have high hardness and good toughness and are suitable for grinding steel. Silicon carbide abrasives are harder, sharper, and have better thermal conductivity, but are brittle and suitable for grinding cast iron and hard alloys.
Due to the different thickness of the grinding wheel, the surface roughness and processing efficiency of the workpiece after processing are different. The coarse abrasive grains are used for rough grinding, the fine abrasive grains are suitable for fine grinding, the coarser the abrasive is, the smaller the grain size is.
The binder acts to bond the abrasive. Ceramic binders are commonly used, followed by resin binders. Different binder materials affect the corrosion resistance, strength, heat resistance and toughness of the grinding wheel.
The harder the abrasive grain bond is, the less likely it is to fall off the grinding wheel. The hardness of the grinding wheel, that is, the hardness of the grinding wheel, refers to the difficulty of the abrasive grains on the surface of the grinding wheel falling off under the action of external force. Easy to fall off is called soft, otherwise it 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 edge (edge) of the abrasive grain is not easy to wear, so that the abrasive grain can be used for a longer period of time, that is, the grinding wheel (harder wheel with higher hardness) can be firmly bonded. Conversely, a grinding wheel with a low hardness is suitable for grinding workpieces with high hardness.
The grinding wheel works under high speed conditions. In order 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, the dynamic balance test should be carried out before use.
After the grinding wheel has been working for a certain period of time, the surface gap will be blocked by the grinding debris, the sharp angle of the abrasive will be blunt, and the original geometry will be distorted. It must therefore be trimmed to restore cutting power and the correct geometry. The grinding wheel needs to be trimmed with a diamond pen.
Grinding is a method of cutting a workpiece with a grinding wheel as a cutting tool on a grinding machine. The characteristics of this method are:
(1) Since the grinding wheel itself has high hardness and heat resistance, the grinding can process materials with high hardness, such as hardened steel and hard alloy.
(2) The characteristics of the grinding wheel and the grinding machine determine that the grinding process system can make 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 drive, so grinding can economically achieve high machining accuracy (IT6~IT5) and small surface roughness (Ra=0.8~0.2μm). Grinding is one of the main methods of finishing parts.
(3) The temperature in the grinding zone is high due to severe friction. 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 can also act as chipping and lubrication.
(4) The radial force during grinding is large. This causes the machine-grinding-workpiece system to retreat so that the actual depth of cut is less than the nominal depth of cut. Therefore, when the grinding is about to be completed, the knife should not be used for light grinding to eliminate the error.
(5) After the abrasive grain is blunt, the grinding force also increases, causing the abrasive grain to break or fall off, and the sharp edge is re-exposed. This characteristic is called "self-sharpness". Self-sharpening makes grinding at a certain time. The internal energy can be carried out normally, but after a certain working time, manual trimming should be carried out to avoid the vibration, noise and damage to the surface quality of the workpiece caused by the increase of the grinding force.
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