Grinders can process materials with high hardness, such as hardened steel and cemented carbide. It can also process brittle materials, such as glass and granite. The grinder can have high grinding accuracy, small surface roughness and high grinding efficiency, such as strong grinding. Grinding belongs to finish machining in machining (machining is divided into rough machining, finish machining, heat treatment and other machining methods), with less machining volume and high precision. It is widely used in machinery manufacturing. When grinding carbon tool steel and carburized and hardened steel parts, a large number of regularly arranged cracks-grinding cracks often appear on the surface basically perpendicular to the grinding direction, which not only affects the appearance of parts, but also directly affects the quality of parts.
Grinding refers to the processing method of removing excess materials from the workpiece with abrasives and abrasives. According to different technological purposes and requirements, there are many grinding methods. In order to meet the needs of development, grinding technology is developing towards precision, low roughness, high efficiency, high speed and automatic grinding. Compared with other cutting methods such as turning, milling and planing, grinding has the following characteristics:
(1) The grinding speed is very high, reaching 30m ~ 50m per second, and the grinding temperature is high, reaching1000℃ ~1500℃; The duration of the grinding process is very short, only about one tenth of a second.
(2) The grinding accuracy is high and the surface roughness is small.
(3) Grinding can not only process soft materials, such as unhardened steel and cast iron, but also process hardened steel and hard materials that other tools cannot process, such as ceramics and cemented carbide.
(4) When grinding, the cutting depth is very small, and the metal layer that can be removed in one stroke is very thin.
(5) During grinding, a large number of tiny abrasive chips fly out from the grinding wheel, while a large number of metal chips splash out from the workpiece. Abrasive chips and metal chips will harm the operator's eyes, and not inhaling the dust in the lungs will also be harmful to the body.
(6) The grinding wheel may break during grinding due to poor quality, improper storage, improper selection of specifications and models, eccentric installation or excessive feed speed, which may cause serious injuries to workers.
(7) When manual operations are carried out near the rotating grinding wheel, such as grinding tools, cleaning workpieces or incorrect grinding wheel calibration methods, workers' hands may come into contact with the grinding wheel or other moving parts of the grinding machine and be injured.
(8) The noise generated during grinding can reach above 1 10dB, which will affect health if noise reduction measures are not taken.
Grinding is used to process internal and external cylindrical surfaces, conical surfaces and planes of various workpieces, as well as special and complicated molding surfaces such as threads, gears and splines. Because of the high hardness of abrasive particles and the self-sharpening of abrasive tools, grinding can be used to process various materials, including hardened steel, high-strength alloy steel, cemented carbide, glass, ceramics and marble and other high-hardness metal and non-metal materials. Grinding speed refers to the linear speed of grinding wheel, which is generally 30 ~ 35 m/s, and when it exceeds 45 m/s, it is called high-speed grinding.
Grinding is usually used for semi-finishing and finishing, and the accuracy can reach IT8 ~ 5 or even higher. General surface roughness is Ra 1.25 ~ 0. 16 micron, precision grinding is Ra 0. 16 ~ 0.04 micron, ultra-precision grinding is Ra0.04~0.0 1+0 micron, and mirror grinding can reach Ra 0. The specific power of grinding (or specific energy consumption, that is, the energy consumed by removing materials per unit volume of workpiece) is greater than that of general cutting, and the metal removal rate is less than that of general cutting. Therefore, before grinding, most of the machining allowance is usually removed by other cutting methods, leaving only the grinding allowance below 0.1~1mm. With the development of high-efficiency grinding technology such as slow feed grinding and high-speed grinding, parts can be directly ground from blanks. Grinding is also used for rough machining, such as grinding off the riser of castings, flash of forgings, ingot skins, etc.
With the increase of the number of high-precision and high-hardness mechanical parts and the development of precision casting and precision forging technology, the performance, variety and output of grinding machines are constantly improving and increasing.
(1) cylindrical grinder: it is a common basic series, mainly used for grinding the outer surfaces of cylinders and cones.
(2) Internal grinder: it is a common basic series, mainly used for grinding the internal surfaces of cylinders and cones. In addition, there are grinders for grinding internal and external circles.
(3) Coordinate grinder: internal grinder with precise coordinate positioning device.
(4) Centerless grinder: the workpiece is kept centerless and generally supported between the guide wheel and the bracket. The guide wheel drives the workpiece to rotate, which is mainly used for grinding cylindrical surfaces. Such as bearing shaft support.
(5) Surface grinder: a grinder mainly used for grinding the workpiece plane. Manual grinding machine is suitable for machining workpieces with small size and high precision, and can process all kinds of irregular workpieces, including cambered surfaces, planes and grooves. B, large water mill is suitable for processing larger workpieces, and the processing accuracy is not high, which is different from hand grinding.
(6) Abrasive belt grinder: a grinder that grinds with a rapidly moving abrasive belt.
(7) Honing machine: it is mainly used to process various cylindrical holes (including smooth holes, axial or radial discontinuous faces, through holes, blind holes and multi-step holes), and can also process conical holes, elliptical holes and trochoid holes.
(8) Grinder: a grinder used to grind the planar or cylindrical inner and outer surfaces of workpieces.
(9) Guide grinder: a grinder mainly used for grinding the guide surface of machine tools.
(10) Tool grinder: a grinder for grinding tools.
(1 1) Multi-purpose grinder: It is used to grind the inner and outer surfaces or planes of cylinders and cones, and can cooperate with servo devices and accessories to grind various workpieces.
(12) special grinder: a special machine tool for grinding some parts. According to its processing objects, it can be divided into spline shaft grinder, crankshaft grinder, cam grinder, gear grinder, thread grinder, curve grinder and so on.
(13) end grinder: a grinder used for grinding the end face of gears.
The main types of CNC grinding machine grinding:
1, cylindrical grinding
It is mainly used for grinding the excircle, outer conical surface and shoulder end face of shaft workpieces on the excircle grinder. When grinding, the workpiece rotates at a low speed. If the workpiece reciprocates longitudinally at the same time, after each single stroke or double stroke of longitudinal movement, the grinding wheel is fed transversely relative to the workpiece, which is called longitudinal grinding method. If the width of the grinding wheel is greater than the length of the grinding surface, the workpiece will not move longitudinally during grinding, but the grinding wheel will continuously feed transversely relative to the workpiece. This method is called plunge grinding. Generally speaking, the efficiency of plunge grinding method is higher than that of longitudinal grinding method. If the grinding wheel is trimmed into a molding surface, it can be cut into an outer surface that can be molded by grinding.
2. Internal grinding
Mainly used for grinding cylindrical holes, conical holes and hole end faces of workpieces on internal grinder, universal external grinder and coordinate grinder. Generally, the longitudinal grinding method is adopted. When grinding the inner surface, the cut-in grinding method can be used. When grinding the inner hole on the coordinate grinder, the workpiece is fixed on the workbench, and the grinding wheel not only rotates at high speed, but also makes planetary motion around the center line of the ground hole. When grinding the inner circle, the grinding speed is often lower than 30m/s due to the small diameter of the grinding wheel.
3. Surface grinding
Mainly used for grinding planes, grooves, etc. On the surface grinder. There are two kinds of surface grinding: cylindrical grinding is used to grind the cylindrical surface of grinding wheel, and generally a horizontal axis surface grinder, such as forming grinding wheel, can also process various forming surfaces; End grinding with grinding wheel is called end grinding, and vertical axis surface grinder is generally used.
4. Centerless grinding
Usually, the excircle of the workpiece is ground on a centerless grinder. When grinding, the workpiece is not centered and supported by the center, but placed between the grinding wheel and the guide wheel, supported by the lower support plate and driven by the guide wheel to rotate. When the axis of the guide wheel and the axis of the grinding wheel are adjusted at an oblique angle of1~ 6, the workpiece can automatically move longitudinally along the axis while rotating, which is called through grinding. Through grinding can only be used to grind the outer cylindrical surface. When cutting-in centerless grinding is adopted, the axis of the guide wheel and the axis of the grinding wheel must be adjusted to be parallel to each other, so that the workpiece is supported on the support plate and does not move axially, and the grinding wheel continuously feeds transversely relative to the guide wheel. Cutting into centerless grinding can process the forming surface. Centerless grinding can also be used to grind the inner circle. During machining, the excircle of the workpiece is supported on the roller or supporting block for centering, the eccentric electromagnetic suction ring is used to drive the workpiece to rotate, and the grinding wheel extends into the hole for grinding. At this time, the outer circle is used as the positioning benchmark to ensure that the inner circle and the outer circle are concentric. Centerless internal grinding is often used to grind the inner channel of bearing ring on a special grinding machine for bearing ring.