Surface finishing of mechanical parts, talk about the scope and characteristics of grinding

Grinding is a kind of cutting process in which the high-speed rotation of the grinding wheel is used as the main motion, and the low-speed rotation and linear movement of the workpiece (or the movement of the grinding head) is used as the feed motion to cut off the excess metal layer on the workpiece. Grinding is one of the most common processing methods in machine building.

Grinding has a wide range of applications, including inner and outer cylindrical surfaces, inner and outer conical surfaces, flat surfaces, forming surfaces and combined surfaces. Grinding can process highly hard, superhard materials that are difficult to machine with other cutting methods, such as hardened steel, high strength alloys, carbides and ceramics. Grinding can also be used for rough processing (grinding billets, cutting risers, etc.), roughing, finishing and superfinishing.
The grinding wheel used for grinding is a special tool. Each abrasive grain is equivalent to one tooth. The whole grinding wheel is equivalent to a large knife with a large number of teeth.

When grinding, the abrasive grains with sharp edges and corners cut fine chips from the surface of the workpiece; abrasive particles that are blunt or less convex can only draw fine grooves on the surface of the workpiece; The abrasive particles produce sliding friction with the surface of the workpiece, and the latter two abrasive grains generate fine dust during grinding. Therefore, the grinding process differs from the general cutting process in that it has scribing and polishing action in addition to the cutting action.

 

(1) The cutting edge of the grinding wheel is irregular. The shape, size, and distribution of the cutting edges are in an irregular random state, usually with a large negative rake angle and a small relief angle.

(2) The grinding allowance is small and the machining accuracy is high. In addition to the high-speed, powerful grinding that can be used to machine blanks, roughing and semi-finishing must be performed before grinding the workpiece. Grinding and finishing IT7IT5, the surface roughness can reach Ra0.80.2μm. With the high-precision grinding method, the surface roughness can reach Ra0.10.006μm.

 

(3) High grinding speed and high temperature. The general grinding speed is about 35m/s, and it can reach 60m/s during high-speed grinding. At present, the grinding speed has been developed to 120m/S. However, during the grinding process, the grinding wheel has a strong pressing and friction effect on the workpiece, and a large amount of cutting heat is generated, and the instantaneous temperature in the grinding region can reach about 1000 °C. In the production practice, in order to reduce the cutting temperature during grinding, it is necessary to add a large amount of cutting fluid, reduce the amount of backing knife, appropriately reduce the grinding wheel speed and increase the workpiece rotation speed.

 

(4) Strong adaptability. As far as the workpiece material is concerned, both soft and hard materials can be ground; in terms of the surface of the workpiece, many surface quality requirements can be processed; in addition, various complicated tools can be sharpened.

(5) The grinding wheel is self-sharp. During the grinding process, the abrasive grains of the grinding wheel gradually become dull, and the cutting resistance acting on the abrasive grains will increase, causing the blunt abrasive grains to break and fall off, exposing the sharp cutting edge to continue cutting, which is the sharpening of the grinding wheel. Sex. It enables the grinding wheel to maintain good cutting performance.