Grinding 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. The principle is to use high-speed rotating grinding wheel and other abrasives to process the surface of the workpiece. 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.

Grinding 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. Cylindrical surface grinding

Grinders are mainly carried out on cylindrical grinders, which are used to grind the excircle, outer conical surface and end face of shaft workpieces. When grinding, the workpiece rotates at a low speed. If the workpiece moves longitudinally back and forth at the same time, and each grinding wheel moves transversely relative to the workpiece after single stroke or double stroke, it is called longitudinal grinding method (Figure 1). 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.

Internal grinding

Mainly used for grinding cylindrical holes (Figure 2), 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.

plane grinding

Mainly used for grinding planes, grooves, etc. On the surface grinder. There are two kinds of surface grinding: cylindrical grinding (Figure 3) is used to grind the cylindrical surface of grinding wheel, generally using horizontal axis surface grinding machine, such as forming grinding wheel, and can also process various forming surfaces; End grinding with grinding wheel is called end grinding, and vertical axis surface grinder is generally used.

centerless grinding

Grinding and grinding tools are generally carried out on a centerless grinder to grind the excircle of the workpiece. 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 (Figure 4). 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. Compared with other cutting methods such as turning, milling and planing, the grinding features are as follows: (1) the grinding speed is very high, reaching 30m ~ 50m per second and the grinding temperature is high, reaching1000 "c ~1500oc; 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, cast iron and nonferrous metals, 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. Wear debris and metal debris will harm the operator's eyes, and not inhaling dust from 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. Processing technology grinding refers to the processing method of removing excess materials from the workpiece with abrasives and abrasives. According to different technological purposes and requirements, grinding technology has many forms. In order to meet the needs of development, grinding technology is developing towards precision, low roughness, high efficiency, high speed and automatic grinding. There are many kinds of grinding methods, mainly grinding with grinding wheel in production. In order to facilitate the use and management, grinding methods are usually divided into four ways according to the grinding form and processing object of grinder products: 1. According to the grinding accuracy, it can be divided into rough grinding, semi-fine grinding, fine grinding, mirror grinding and ultra-precision machining. 2. According to the feed form, it is divided into cutting grinding, longitudinal grinding, slow feed grinding and no feed grinding. Quantitative grinding. 3. Belt grinding, centerless grinding, end grinding, peripheral grinding, wide grinding wheel grinding, form grinding, profiling grinding, oscillating grinding, high-speed grinding, strong grinding, constant pressure grinding, manual grinding, dry grinding, wet grinding, grinding, honing, etc. 4. Cylindrical grinding, internal grinding, plane grinding and edge grinding (depending on the machined surface). For example, according to the types of grinding tools used, it can be divided into: fixed abrasive grinding methods and free abrasive particle grinding methods. The grinding methods of fixed abrasive tools mainly include grinding wheel grinding, honing, belt grinding, electrolytic grinding and so on. The processing methods of free abrasive grinding mainly include grinding, polishing, jet machining, abrasive flow machining, vibration machining and so on. According to the linear speed vs of grinding wheel, it can be divided into: ordinary grinding vs.

Internal grinder In 1930s, in order to adapt to the hardening of watches, bicycles, sewing machines and firearms, Britain, Germany and the United States developed grinders using natural grinding wheels respectively. These grinders were modified by adding grinding heads to existing machine tools such as lathes and planers at that time. They are simple in structure, low in rigidity, easy to generate vibration when grinding, and require operators to have high technology to grind precision workpieces. 1876 The universal cylindrical grinder manufactured by Brown-Sharp Company of the United States exhibited in Paris Expo is the first machine with the basic characteristics of modern grinder. The headstock and tailstock of the workpiece are installed on the reciprocating worktable, and the box-shaped lathe bed improves the rigidity of the machine tool and has internal grinding accessories. 1883 this company made a surface grinder, with the grinding head mounted on the column and the workbench moving back and forth. 1900 or so, the development of artificial abrasives and the application of hydraulic transmission have greatly promoted the development of grinding machines. With the development of modern industry, especially automobile industry, various types of grinding machines have come out one after another. For example, at the beginning of the 20th century, planetary internal grinder, crankshaft grinder, camshaft grinder and electromagnetic sucker piston ring grinder were developed successively. The automatic measuring device is applied to 1908 grinder. Around 1920, centerless grinders, double-head grinders, roller grinders, guideway grinders, honing machines and superfinishing machine tools were successively manufactured and used. In 1950s, a high-precision cylindrical grinder for mirror grinding appeared. At the end of 1960s, high-speed grinders and surface grinders with large cutting depth and slow feed grinding appeared. In 1970s, digital control and microprocessor adaptive control technology were widely used in grinding machines. Classification of grinding machines 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.

Surface grinder (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. 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. (5) Surface grinder: a grinder mainly used for grinding the workpiece plane. (6) Abrasive belt grinder: a grinder that grinds with a rapidly moving abrasive belt. (7) Honing machine: a grinder used for honing various surfaces of workpieces.

Coordinate grinder (8) grinder: a grinder used to grind the plane 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.

Cylindrical grinder (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. Safety protection grinding is widely used and is one of the main methods for precision machining of mechanical parts. However, due to the high speed of the grinding wheel of the grinder, the grinding wheel is hard and brittle, which can not withstand the heavy impact. Improper accidental operation will cause very serious consequences. Therefore, the safety technical work of grinding is particularly important, and reliable safety protection devices must be adopted to concentrate on the operation to ensure foolproof. In addition, fine sand and metal chips splashed on the grinding wheel workpiece will hurt workers' eyes. If workers inhale a lot of this dust, it will be harmful to their health, and appropriate protective measures should be taken. Some safety technical problems that should be paid attention to in grinding. Safety in use: 1. Before starting, the machine tool should be carefully and comprehensively inspected, including the inspection of the control mechanism, electrical equipment, magnetic chuck and other fixtures. After inspection, lubrication should be carried out. After lubrication, it should be tested and confirmed to be in good condition before use. 2. Pay attention to correct clamping when loading the workpiece. In the grinding process, the loosening of the workpiece will cause the workpiece to fly out and hurt people or the grinding wheel to break. At the beginning of work, manual adjustment should be used to make the grinding wheel slowly approach the workpiece, and the initial feed should be small to avoid the grinding wheel colliding with it. When it is necessary to control the reciprocating motion of the workbench with a stop iron, it should be accurately adjusted according to the grinding length of the workpiece, and the stop iron should be tightened. 3. When replacing the grinding wheel, visual inspection must be carried out first. If there is trauma, knock it with a wooden hammer or stick. The sound is required to be clear and not cracked. When installing grinding wheels, they must be assembled according to the specified methods and requirements. After static balance debugging, you can install the test. You can't use it until everything is normal. 4. Workers should wear protective glasses at work, balance dressing grinding wheel to prevent collision. Measuring the workpiece, adjusting or wiping the machine tool should be carried out after stopping the machine. When using the magnetic sucker, clean the disk surface and the workpiece, tighten it and suck it firmly, and if necessary, add an iron stopper to prevent the workpiece from shifting or flying out. Pay attention to the installation of grinding wheel protective cover or machine tool baffle, and stand in front of high-speed rotating grinding wheel. The grinder shall be maintained and used by special personnel, and shall be overhauled regularly to ensure that the machine tool is in good condition. After 1. operation, all parts of machine parts, especially sliding parts, should be cleaned and oiled. 2. Remove the debris from all parts of Jiande grinder. 3, the necessary parts, rust. Maintenance precautions of the above grinder 1. Please correct the grinding wheel balance before grinding. 2. The grinding wheel must be carefully selected according to the material and hardness of the workpiece. 3. The spindle end and grinding wheel flange should be coated with thin oil film to prevent rust. 4. Please pay attention to the direction of spindle rotation. 5. It is forbidden to use air guns to clean crops and machines. 6, please pay attention to whether the cable is loose, really adjust. 7. Please pay attention to whether the oil channel of the oil window is clear. 8. Please use Mobil # 1405 to replace the fuel tank every 3-6 months. (It is advisable to change the oil once every 1-2 months at the beginning) 9. Adjust the oil adjusting screw to an appropriate level, whether it is reduced or increased. 10, dust box, filter steel, please clean it once a week. 1 1, when the suction is weak, please check whether the suction pipe is blocked. 12, the vacuum pipe must be kept clean, otherwise it will cause combustion. The grinding wheel is a circular consolidated grinding tool with a through hole in the center, which is made of abrasive and adhesive resin. Grinding wheel is one of the most widely used grinding tools. When in use, it rotates at a high speed, and can perform rough grinding, semi-fine grinding, fine grinding, grooving and cutting on the outer circle, inner circle, plane and various contours of metal or nonmetal workpieces. Classification of grinding wheels The grinding wheel is the one with the largest consumption and the widest application. When in use, it rotates at high speed, and can perform rough grinding, semi-fine grinding, grooving and cutting on various surfaces of metal or nonmetal workpieces. There are many kinds of grinding wheels. 1. According to the abrasives used, it can be divided into ordinary abrasives (corundum, silicon carbide, etc. ) grinding wheel, natural abrasive and superhard abrasive (diamond, cubic boron nitride, etc. ) grinding wheel; 2. According to the shape, it can be divided into plane grinding wheel, inclined grinding wheel, cylindrical grinding wheel, cup grinding wheel and dish grinding wheel. 3. According to the binder, it can be divided into ceramic grinding wheel, resin grinding wheel, rubber grinding wheel and metal grinding wheel. The characteristic parameters of grinding wheel mainly include abrasive, viscosity, hardness, binder, shape and size. Because the grinding wheel usually works at high speed, it is necessary to carry out a rotation test (to ensure that the grinding wheel will not break at the highest working speed) and a static balance test (to prevent the vibration of the machine tool when working) before use. After working for a period of time, the grinding wheel should be dressed to restore grinding performance and correct geometry. Matters needing attention in the safe installation of grinding wheel

When installing, first check the safety and quality of the grinding wheel. Method: Tap the side of the grinding wheel with a nylon hammer (or pen), and the sound will be clear. (1) The positioning of the installation position of the grinder is our first consideration in the installation process. Only when a reasonable and suitable post is selected can other work be carried out. It is forbidden to install the grinder in a place facing nearby equipment and operators or where people often pass by. Generally, a special grinding wheel room should be set up in a larger workshop. If it is really impossible to set up a special grinding wheel room due to the terrain limitation of the workshop, a protective baffle with a height not less than 1.8m should be installed on the front of the grinder, and the baffle should be firm and effective. (2) Balance problem The imbalance of the grinding wheel is mainly due to the inaccurate manufacture and installation of the grinding wheel, which makes the center of gravity of the grinding wheel not coincide with the rotating shaft. The harm caused by imbalance is mainly manifested in two aspects. On the one hand, when the grinding wheel rotates at high speed, it causes vibration, which is easy to cause polygonal vibration marks on the surface of the workpiece; On the other hand, unbalance accelerates the vibration of the spindle and the wear of the bearing, which will cause the grinding wheel to break and even cause an accident. Therefore, it is required that the sand office building with a height greater than or equal to 200mm should be statically balanced after the chuck is installed, and the grinding wheel should be repeatedly statically balanced after dressing or finding imbalance during work. (3) Matching problem Matching problem mainly refers to the installation and matching of chuck and grinding wheel. According to the standard requirements, the diameter of the grinding wheel chuck shall not be less than 1/3 of the diameter of the office building with installed sand, and it is stipulated that when the diameter of the grinding wheel is larger than the diameter of the chuck 10mm, a new grinding wheel shall be replaced. In this way, there is a matching problem between chuck and grinding wheel, otherwise such a situation will occur, and "big horse-drawn cart" will cause waste of equipment and materials; The "small horse-drawn cart" does not meet the safety requirements and is easy to cause personal accidents. Therefore, the reasonable matching of chuck and grinding wheel can save equipment and cut materials on the one hand; On the other hand, it meets the requirements of safe operation. In addition, a buffer pad with a diameter 2mm larger than that of the chuck and a thickness of 1mm~2mm should be installed between the grinding wheel and the chuck. 4) Protection: The protective cover is the most important protective device of the grinder. Its function is to effectively cover the grinding wheel fragments when the grinding wheel is damaged for some reason during work, and ensure the safety of personnel. The grinding wheel guard plate has two shapes: round and square, and the maximum opening angle is not allowed to exceed 90; The protective cover is made of steel with tensile strength not less than 4 15N/mm2. When replacing a new grinding wheel, the protective cover shall be installed firmly and reliably, and shall not be disassembled or discarded at will. The baffle is one of the main protective accessories of the grinder. When the opening of the protective cover is greater than or equal to 30 (higher than the horizontal plane of the spindle), this device must be set. Its main function is to shield the flying noise during grinding, so as not to hurt the operator. Installed at the positive end of the protective cover opening, its width should be greater than the width of the grinding wheel protective cover, and firmly fixed on the protective cover. In addition, the clearance between the circumferential surface of the grinding wheel and the baffle is required to be less than 6mm. (5) Support problem Support is one of the commonly used accessories for grinding machines. According to the regulations, grinding machines with grinding wheel diameter above 150mm must be equipped with adjustable supports. The distance between the grinding wheel and the bracket should be less than 1/2 of the minimum size of the workpiece to be ground, but the maximum distance should not exceed 3mm(6) Grounding problem The grinder uses the power cord, so the equipment shell must have a good grounding protection device. This is also one of the important factors that are easy to cause accidents.