Application method of grinding wheel for stone in stone grinding process

The grinding wheel for stone is a cutting tool for grinding. It is a porous object made of many small and hard abrasive grains and bonding agents. Abrasive particles are directly responsible for cutting work and must be sharp and have high hardness, heat resistance and certain toughness. Commonly used abrasives are alumina (also known as corundum) and silicon carbide. Alumina-based abrasives have high hardness and good toughness, and are suitable for grinding steel materials. Silicon carbide abrasives have higher hardness, sharper, better thermal conductivity, but are more brittle, suitable for grinding cast iron and cemented carbide.

The grinding wheel for stone of the same abrasive, due to its different thickness, the surface roughness and processing efficiency of the workpiece after processing are different. The coarse abrasive is used for rough grinding, and the finer abrasive is suitable for fine grinding. The coarser the abrasive, the smaller the particle size. The bonding agent acts as a bonding abrasive. Commonly used is ceramic bond, followed by resin bond. Different binder materials affect the corrosion resistance, strength, heat resistance and toughness of the grinding wheel.

The stronger the adhesion of abrasive grains, the less likely it is to fall off the grinding wheel. The hardness of the grinding wheel is called the hardness of the grinding wheel, which refers to the degree of difficulty for the abrasive particles on the surface of the grinding wheel to fall off under the action of 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 edges (edges) of the abrasive grains are not easy to wear, so that the abrasive grains can be used for a longer time, which means that a firmer bonded grinding wheel (a grinding wheel with higher hardness) can be selected. Conversely, a low-hardness grinding wheel is suitable for grinding high-hardness workpieces.

The grinding wheel for stone works under high-speed conditions. In order to ensure safety, it should be checked 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 certain period of time, the surface voids will be blocked by grinding debris, the sharp angle of the abrasive will be blunt, and the original geometric shape will be distorted. Therefore, it must be trimmed to restore cutting ability and correct geometry. The grinding wheel needs to be trimmed with a diamond pen.

　Grinding is a method of cutting a workpiece on a grinding machine with a grinding wheel as a cutting tool. The characteristics of this method are:

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

(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 rigidity of the grinding machine is good; Hydraulic transmission, so grinding can economically obtain 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) Due to severe friction, the temperature in the grinding zone is very high. This will cause stress and deformation of the workpiece, and even burn the workpiece surface. Therefore, a large amount of coolant must be injected during grinding to reduce the grinding temperature. Coolant can also play a role in chip removal and lubrication.

(4) 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 not be carried out to eliminate the error.

(5) After the abrasive grains are blunt, the grinding force will increase, causing the abrasive grains to break or fall off, revealing the sharp edge again. This characteristic is called "self-sharpening". Self-sharpening makes the grinding work in a certain period of time. The internal can work normally, but after a certain working time, manual trimming should be carried out to avoid vibration, noise and damage to the surface quality of the workpiece caused by the increase of the grinding force.

The structure and grinding movement of surface grinder

There are many types of grinders, mainly including surface grinders, cylindrical grinders, internal grinders, universal cylindrical grinders (also for grinding inner holes), gear grinders, thread grinders, guideway grinders, centerless grinders (for external grinding) and tool grinders ( Sharpening tools) and so on. Here we introduce the surface grinder and its movement.

1. The structure of the surface grinder (take M7120A as an example, among which: M--grinding machine type; 71--horizontal axis table surface grinder; 20--table width of 200mm; A--first major improvement.)

(1) Grinding wheel frame-install the grinding wheel and drive the grinding wheel to rotate at a high speed. The grinding wheel frame can move manually or hydraulically along the dovetail guide rail of the sliding seat.

(2) Sliding base---install the wheel stand and drive the wheel stand to move up and down along the column guide rail.

(3) Column-supporting sliding seat and grinding wheel stand.

(4) Workbench---install the workpiece and drive it for reciprocating linear motion by hydraulic system.

(5) Bed-support the worktable and install other parts.

(6) Coolant system-provide coolant (saponified oil) to the grinding area

(7) Hydraulic transmission system-its composition includes:

a. Power element-oil pump, which supplies pressure oil for hydraulic transmission system;

b. Actuating element-is a cylinder, which drives the movement of parts such as the workbench;

c. Control components-various valves, controlling pressure, speed, direction, etc.;

d. Auxiliary components-such as fuel tank, pressure gauge, etc.

Compared with mechanical transmission, hydraulic transmission has the advantages of smooth transmission, overload protection, and stepless speed regulation in a larger range.

2. Surface grinding movement

(1) The main movement-the high-speed rotating movement of the grinding wheel.

(2) Feed movement

a. Longitudinal feed-the worktable drives the reciprocating linear movement of the workpiece;

b. Vertical feed-the movement of the grinding wheel to the depth of the workpiece;

c. Lateral feed-the grinding wheel for stone moves along the gap of its axis.