Introduction Grinding processing is widely used in the mechanical manufacturing industry. Heat treated and quenched carbon tool steels and carburized and hardened steel parts often have a large number of regularly arranged cracks on the surface perpendicular to the grinding direction during grinding. - Grinding cracks, which not only affect the appearance of the part, but more importantly, directly affect the quality of the part.
The principle uses a high-speed rotating grinding wheel or the like to machine the machining of the workpiece surface. Grinding is used to machine the inner and outer cylindrical faces, conical faces and planes of various workpieces, as well as special and complex forming surfaces such as threads, gears and splines.
Grinding Due to the high hardness of the abrasive particles, the grinding tools are self-sharpening. Grinding can be used to process a variety of materials, including hardened steel, high-strength alloy steel, hard alloys, glass, ceramics and marble. And non-metallic materials. The grinding speed refers to the linear speed of the grinding wheel, which is generally 30 to 35 m/s. When it exceeds 45 m/s, it is called high speed grinding. Grinding is usually used for semi-finishing and finishing. The precision is up to IT8~5 or even higher. The surface roughness is generally ground to Ra1.25~0.16μm. The precision grinding is Ra0.16～0.04μm. Ultra-precision grinding The cutting is Ra 0.04 to 0.01 μm, and the mirror grinding can reach Ra 0.01 μm or less. The specific power of grinding (or specific energy consumption, that is, the energy consumed to cut off a unit of workpiece material) is larger than that of general cutting, and the metal removal rate is smaller than that of general cutting. Therefore, the workpiece is usually removed by other cutting methods before grinding. For most machining allowances, only a grinding allowance of 0.1 to 1 mm or less is left. With the development of high-efficiency grinding such as slow-feed grinding and high-speed grinding, parts can be directly ground from the blank. Grinding is also used as a waste processing, such as grinding the riser of the casting, the flash of the forging, and the outer skin of the steel ingot.
Type external grinding
Mainly on the cylindrical grinding machine to grind the outer cylinder, outer cone and shoulder end face of the shaft workpiece. During grinding, the workpiece rotates at a low speed. If the workpiece is reciprocated longitudinally and the grinding wheel is fed laterally relative to the workpiece after each single stroke or double stroke in the longitudinal direction, it is called longitudinal grinding (Fig. 1). If the width of the grinding wheel is larger than the length of the surface to be ground, the workpiece does not move longitudinally during the grinding process, but the grinding wheel continuously feeds the workpiece continuously, which is called the plunge grinding method. Generally, the efficiency of the cutting method is higher than that of the longitudinal grinding method. If the grinding wheel is trimmed into a forming surface, the incision grinding method can process the formed outer surface.
Internal grinding
It is mainly used for grinding cylindrical holes (Fig. 2), tapered holes and hole end faces of internal grinding machines, universal cylindrical grinding machines and coordinate grinding machines. Longitudinal grinding is generally used. When grinding the inner surface, a plunge grinding method can be used. When grinding the inner hole on the coordinate grinding machine, the workpiece is fixed on the workbench. In addition to the high-speed rotation, the grinding wheel also performs planetary motion around the center line of the grinding hole. In the case of internal grinding, the grinding speed is often less than 30 m/s due to the small diameter of the grinding wheel.
Surface grinding
Mainly used to grind planes, grooves, etc. on a surface grinder. There are two types of surface grinding: grinding with the outer surface of the grinding wheel is called peripheral grinding (Fig. 3). Generally, a horizontal surface grinder is used. For example, various forming surfaces can be processed by using a grinding wheel; grinding with a grinding wheel end face It is called end face grinding and generally uses a vertical axis surface grinder.
Centerless grinding
It is usually carried out on a centerless grinding machine to grind the outer circumference of the workpiece. When grinding, the workpiece is not centered and supported, but placed between the grinding wheel and the guide wheel, supported by the lower plate and driven by the guide wheel. When the axis of the guide wheel and the axis of the grinding wheel are adjusted to be obliquely 1° to 6°, the workpiece can automatically perform longitudinal longitudinal movement along the axial direction while rotating, which is called through-grinding (Fig. 4). Through-grinding can only be used to grind the outer cylindrical surface. When the plunging centerless grinding is used, 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 pallet without axial movement, and the grinding wheel is continuously fed transversely with respect to the guide wheel. Plunge centerless grinding can machine the forming surface. Centerless grinding can also be used for internal grinding. When machining, the outer circumference of the workpiece is supported on the roller or the support block, and the workpiece is rotated by the eccentric electromagnetic suction ring. The grinding wheel is inserted into the hole for grinding. At this time, the outer circle is used for positioning. The benchmark ensures that the inner circle is concentric with the outer circle. Centerless internal grinding is often used to grind the inner ring of a bearing ring on a special grinding machine for bearing rings. Grinding characteristics Compared with other cutting methods, such as turning, milling, planing, etc., it has the following characteristics:
(1) The grinding speed is very high, up to 30m~50m per second; the grinding temperature is high, up to 1000â€C～1500oC; the grinding process lasts for a short time, only about one tenth of a second.
(2) Grinding processing can achieve high machining accuracy and small surface roughness values.
(3) Grinding can not only process soft materials, such as untempered steel, cast iron and non-ferrous metals, but also hard materials such as porcelain and hard alloys that cannot be processed by hardened steel and other tools.
(4) The depth of cut during grinding is small, and the metal layer that can be removed in one stroke is thin.
(5) When grinding, a large amount of fine grinding debris is scattered from the grinding wheel, and a large amount of metal chips are splashed from the workpiece. Wear debris and metal shavings can cause damage to the operator's eyes, and dust that is not inhaled into the lungs can be harmful to the body.
(6) Due to poor quality of the grinding wheel, poor storage, improper selection of specifications and models, eccentricity of installation, or excessive feed rate, the grinding wheel may be broken during grinding, which may cause serious injury to workers.
(7) When manual operation is performed near a rotating grinding wheel, such as grinding tool, cleaning workpiece or grinding wheel correction method, the worker's hand may be injured by the grinding wheel or other moving parts of the grinding machine.
(8) The noise generated during grinding can be up to 110dB or more. If no noise reduction measures are taken, it will also affect health.
Grinding process refers to the processing method of using abrasives and abrasive tools to remove excess materials on the workpiece. According to the purpose and requirements of the process, the grinding process has various forms. In order to meet the development needs, the grinding technology is towards precision and low. Roughness, high efficiency, high speed and automatic grinding direction. There are many forms of grinding processing methods. In production, grinding is mainly carried out by grinding wheels. For the convenience of use and management, the grinding processing method is generally divided into four modes according to the grinding processing form of the grinding machine product and its processing object:
1. According to the grinding precision, coarse grinding, semi-finishing, fine grinding, mirror grinding, super finishing.
2. According to the feed form, the cutting is divided into grinding, longitudinal grinding, slow-feed grinding, no feed grinding, constant pressure grinding, and quantitative grinding.
3. Grinding belt grinding according to grinding form, centerless grinding, end grinding, peripheral grinding, wide grinding wheel grinding, profile grinding, profile grinding, oscillating grinding, high speed grinding, strong grinding, Constant pressure grinding, manual grinding, dry grinding, wet grinding, grinding, honing, etc.
4. According to the machining surface, external grinding, internal grinding, surface grinding and sharpening (gear grinding and thread grinding) In addition, there are many different methods, such as those used in grinding. The types of grinding tools are divided into: grinding method for solidified abrasive grinders and grinding method for free abrasive grinders. Grinding methods for solidified abrasive grinders mainly include grinding of grinding wheels, honing, and abrasive belts. Grinding, electrolytic grinding, etc.; processing methods for free abrasive grinding mainly include grinding, polishing, jet processing, abrasive flow processing, vibration processing, etc. According to the height of the grinding wheel line speed Vs: ordinary grinding Vs=150m/ s. According to the new technology used: magnetic grinding, electrochemical polishing, etc.
A grinding machine is a machine tool that grinds the surface of a workpiece with a grinding tool.
Most grinders are ground using high-speed rotating grinding wheels. A few are processed with other abrasives such as oilstone, abrasive belts and free abrasives, such as honing machines, superfinishing machines, belt grinders, grinders and polishing. Machine and so on.
Grinding machines can process harder materials such as hardened steel and hard alloys; they can also process brittle materials such as glass and granite. The grinding machine can perform grinding with high precision and surface roughness, as well as high-efficiency grinding, such as strong grinding.
In the 1830s, in order to adapt to the hardening of parts such as watches, bicycles, sewing machines and firearms, the grinding machines using natural abrasive grinding wheels were developed in the UK, Germany and the United States. These grinders were modified from the existing machine tools such as lathes and planers. They are simple in structure, low in rigidity, and easy to generate vibration during grinding. The artifacts.
The universal cylindrical grinding machine manufactured by Brown-Sharp Company of the United States exhibited at the Paris Exposition in 1876 was the first machine to have the basic characteristics of a modern grinding machine. Its workpiece headstock and tailstock are mounted on a reciprocating workbench that increases machine rigidity and has an internal grinding attachment. In 1883, the company made a surface grinder with a grinding head mounted on a column and a reciprocating table.
Around 1900, the development of artificial abrasives and the application of hydraulic transmissions have greatly promoted the development of grinding machines. With the development of modern industry, especially the automobile industry, various types of grinding machines have been introduced. For example, at the beginning of the 20th century, planetary inner grinding machines, crankshaft grinding machines, camshaft grinding machines and piston ring grinding machines with electromagnetic chucks were developed.
The automatic measuring device was applied to the grinding machine in 1908. Before and after 1920, centerless grinders, double-face grinders, roll grinders, guide grinders, honing machines and superfinishing machines were used one after another; in the 1950s, high-precision cylindrical grinders for mirror grinding were introduced; At the end of the year, there were high-speed grinders with a line speed of 60-80 m/s and large depth-cutting and slow-feed grinding surface grinders. In the 1970s, digital control and adaptive control technologies using microprocessors were widely used on grinding machines. Applications.
Grinding Machine Classification With the increase in the number of high-precision, high-hardness mechanical parts and the development of precision casting and precision forging processes, the performance, variety and output of grinding machines are constantly increasing and increasing.
Surface Grinder
(1) Cylindrical grinding machine: It is a common type of basic type, mainly used for grinding grinding machines with cylindrical and conical outer surfaces.
(2) Internal grinding machine: It is a common type of basic type, mainly used for grinding grinding machines with cylindrical and conical inner surfaces.
(3) Coordinate grinding machine: an internal grinding machine with a precision coordinate positioning device.
(4) Centerless grinding machine: the workpiece is uncentered, generally supported between the guide wheel and the bracket, and the workpiece is rotated by the guide wheel, which is mainly used for grinding the cylindrical surface.
(5) Surface Grinding Machine: A grinding machine mainly used for grinding the plane of a workpiece.
(6) Belt Grinding Machine: A grinding machine that grinds with a fast moving belt.
(7) Honing machine: A grinding machine for honing various surfaces of workpieces. Coordinate grinding machine
(8) Grinder: A grinding machine for grinding the inner or outer surface of a workpiece.
(9) Guide grinding machine: It is mainly used to grind the grinding machine surface of the machine tool.
(10) Tool Grinding Machine: Grinding machine for grinding tools.
(11) Multi-purpose grinding machine: a grinding machine for grinding cylindrical, conical inner and outer surfaces or planes, and capable of grinding a variety of workpieces with followers and accessories.
Cylindrical grinding machine
(12) Special grinding machine: special machine tool for grinding certain parts. According to its processing objects, it can be divided into: spline shaft grinding machine, crankshaft grinding machine, cam grinding machine, gear grinding machine, thread grinding machine, curve grinding machine and so on.
Safety Protection Grinding processing is widely used and is one of the main methods for precision machining of machine parts. However, due to the high rotational speed of the grinding wheel, the grinding wheel is relatively hard, brittle, can not withstand heavy impact, accidental improper operation, crushing the grinding wheel will have very serious consequences. Therefore, the safety technology work of grinding processing is particularly important. It is necessary to adopt reliable safety protection devices, and the operation should be concentrated and guaranteed to be foolproof. In addition, the fine sand and metal scraps splashed on the workpiece of the grinding wheel during grinding may damage the worker's eyes. If the worker inhales the dust in a large amount, it is harmful to the body and appropriate protective measures should be taken. Pay attention to the following safety technical issues when grinding.
Safe use
1. The machine should be thoroughly inspected before driving, including inspection of the control mechanism, electrical equipment and magnetic chucks. After the inspection, it is lubricated, and after lubrication, the test is carried out to confirm that everything is good before use.
2. When loading the workpiece, pay attention to the card being positive and tight. During the grinding process, the looseness of the workpiece will cause the workpiece to fly out of injury or crush the grinding wheel and other serious consequences. When starting work, apply the manual adjustment method to make the grinding wheel slower and closer to the workpiece. The starting feed rate should be small, and the force should not be too strong to prevent the grinding wheel from colliding. When it is necessary to use the iron stop to control the reciprocating motion of the worktable, it is necessary to accurately adjust the length of the workpiece according to the grinding length of the workpiece and tighten the retaining iron.
3. When replacing the grinding wheel, it is necessary to first check the appearance, whether there is any trauma, and then use a wooden hammer or a wooden stick to strike, and the sound is required to be clear and crack-free. When installing the grinding wheel, it must be assembled according to the specified methods and requirements. After static balance adjustment, install it and test it. After everything is normal, it can be used.
4. Workers should wear protective glasses during work, and balance the grinding wheel to prevent impact. Measuring the workpiece, adjusting or wiping the machine must be done after the shutdown. When using a magnetic suction cup, wipe the surface of the disc and the workpiece tightly, and fasten it. If necessary, add a retaining iron to prevent the workpiece from shifting or flying out. Pay attention to the wheel guard or the machine baffle, and the station should be placed on the front side of the high-speed rotating grinding wheel.
Daily maintenance of the grinding machine should be carried out by a person responsible for maintenance and use, regular maintenance to ensure that the machine is in good condition.
1. After the operation is completed, all parts of the machine, especially the sliding parts, should be cleaned and oiled.
2. Remove the grinding debris from all parts of the Jiande grinding machine.
3, the necessary parts, on the rust.
Use the above grinding machine maintenance precautions
1. Before grinding, please correct the balance of the grinding wheel.
2. The grinding wheel must be carefully selected according to the material and hardness of the work.
3. The main shaft end and the grinding wheel flange should be coated with a 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 the work and the machine.
6, please pay attention to whether the cable is loose, and indeed adjust.
7. Please pay attention to whether the oil window oil circuit is smooth.
8. Please use Mobil #1405 in the oil tank to change every 3-6 months. (It is best to change oil once in 1-2 months)
9. The oil adjustment screw is adjusted to the appropriate amount, which is reduced and increased.
10, vacuum box, filter steel, please clean once a week.
11. When the suction is weak, please check if the dust suction pipe is clogged with powder.
12. The suction pipe must be kept clean, otherwise it will cause burning.
Segment grinding wheel A round-shaped fixed abrasive with a through hole in the center made of abrasive and binder resin. The grinding wheel is the largest and the most widely used one. It can be coarsely ground, semi-finished and polished on the outer circle, inner circle, plane and various profiles of metal or non-metal workpieces. Fine grinding and grooving and cutting.
Grinding wheel classification grinding wheel has the largest amount of abrasive material and the widest use surface. It can be rotated at high speed during use. It can grind, semi-finely grind and open the outer circle, inner circle and flat surface of metal or non-metal workpiece. The groove is cut and the like.
1. According to the abrasive used, it can be divided into ordinary abrasive (corundum, silicon carbide, etc.) grinding wheel natural abrasive super-hard abrasive (diamond, cubic boron nitride, etc.) grinding wheel;
2. According to the shape, it can be divided into a flat grinding wheel, a beveling grinding wheel, a cylindrical grinding wheel, a cup-shaped grinding wheel, a dish-shaped grinding wheel, and the like;
3. According to the bonding agent, it can be divided into ceramic grinding wheel, resin grinding wheel, rubber grinding wheel and metal grinding wheel. The grinding wheel characteristic parameters mainly include abrasive, viscosity, hardness, bonding agent, shape and size.
Since the grinding wheel usually works at high speed, the slewing test (to ensure that the grinding wheel will not rupture at the highest working speed) before use should be tested for static balance (to prevent machine vibration during work). After the grinding wheel has been in operation for a period of time, it should be trimmed to restore the correct geometry for the grinding performance.
Precautions during the safe installation of the grinding wheel Firstly, the safety quality of the grinding wheel should be tested. For the method, the side of the grinding wheel can be tapped with a nylon hammer (also with a pen), and the sound is crisp and there is no problem.
(1) Positioning problem Where the grinder is installed is the first problem to be considered in our installation process. Only when a reasonable and appropriate position is selected, we can carry out other work. Grinding machines are forbidden to be installed in the vicinity of the equipment and operators or in places that are often visited. Generally, larger grinder rooms should be installed in the larger workshops. If it is not possible to set up a special grinder house due to the limitation of the topography of the plant, a protective baffle of not less than 1.8 m in height should be installed on the front side of the grinder, and the baffle plate is required to be firm and effective.
(2) Balance problem The imbalance of the grinding wheel is mainly caused by the inaccurate manufacture and installation of the grinding wheel, which makes the center of gravity of the grinding wheel not coincide with the rotary shaft. The damage 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, the imbalance accelerates the vibration of the main shaft and the wear of the bearing. This can cause the grinding wheel to rupture and even cause an accident. Therefore, it is required that the sand office building with a straightness greater than or equal to 200mm should be statically balanced after loading the chuck. The grinding wheel should be statically balanced after being shaped and trimmed or found to be unbalanced during work.
(3) Matching problem matching problem mainly refers to the problem of installation and matching of the chuck and the grinding wheel. According to the standard requirements, the diameter of the grinding wheel chuck should not be less than 1/3 of the diameter of the installed sand office building, and the new grinding wheel should be replaced when the grinding wheel is worn to a diameter larger than the diameter of the chuck by 10 mm. In this way, there is a problem of matching the chuck and the grinding wheel. Otherwise, there will be such a situation that the “large horse-drawn carriage†causes waste of equipment and materials; the “small horse-drawn carriage†does not meet the safety requirements and is liable to cause personal accidents. Therefore, the reasonable matching of the chuck and the grinding wheel can save equipment and cut the material on the one hand, and meet the requirements of safe operation on the other hand. In addition, a cushion with a diameter larger than 2 mm of the chuck and a thickness of 1 mm to 2 mm should be installed between the grinding wheel and the chuck.
(4) Protection problem The protective cover is the most important protection device of the grinder. Its function is: When the grinding wheel is damaged due to work, it can effectively cover the grinding wheel fragments and ensure the safety of personnel. The shape of the wheel guard is round and square, and the maximum opening angle is not allowed to exceed 90°; the material of the shield is steel with a tensile strength of not less than 415 N/mm2. When replacing a new grinding wheel, the protective cover should be installed firmly and reliably, and the protective cover should not be dismantled or discarded.
Blocking the screen is one of the main protective attachments of the grinder. The opening of the guard above the horizontal plane of the main shaft is greater than or equal to 30 (this device must be provided. Its main function is to block the flying during the grinding process, so as not to hurt The operator is installed at the positive end of the protective cover opening, the width should be larger than the width of the wheel guard, and should be firmly fixed to the protective cover. In addition, the clearance between the circumferential surface of the grinding wheel and the baffle should be less than 6mm.
(5) Bracket problem The bracket is one of the commonly used attachments for grinders. The grinders with a diameter of 150 mm or more must be provided with adjustable brackets. The distance between the grinding wheel and the bracket should be less than 1/2 of the minimum shape of the workpiece to be ground, but the maximum should not exceed 3 mm.
(6) Grounding problems Grinding machines use power lines, so the outer casing of the equipment must have good grounding protection. This is also one of the important factors that cause accidents.
Precautions during use
(1) Side grinding problem
In the daily use of the grinder, we often find that some operators do not divide the type of grinder, regardless of the type of grinding wheel, and use the side of the grinding wheel to grind it arbitrarily. This is a serious violation of the safety operation rules. behavior. According to the regulations, the grinding wheel with the circumferential surface as the working surface should not be grounded. The radial strength of the grinding wheel is large and the axial strength is very small. When the operator is too strong, the grinding wheel will be broken and even hurt. In practice This behavior should be prohibited during use.
(2) Positive operation problems
In daily use, many operators are always accustomed to working on the grinding wheel because the direction can be used. In fact, this behavior is a special prohibition in the operation of the grinder. According to the operating procedure, when grinding the workpiece with a grinder, the operator should stand on the side of the grinding wheel and must not operate on the front side of the grinding wheel to avoid the grinding wheel flying out or the grinding wheel breaking out and injuring people when the grinding wheel fails.
(3) Forced operation problems
In the use of grinders, some operators, especially younger operators, are trying to grind quickly and use too much force, which is a very unsafe operation. The flatness of any grinding wheel has a certain strength, which is likely to cause the grinding wheel to break, or even fly out and hurt people, it is also a behavior that should be prohibited.
(4) Common operation problems
In the actual daily operation, there are also such situations. Some people share a grinder and operate at the same time in order to catch up with the production task and grab the working time. This is a serious illegal operation and should be strictly prohibited. When a grinder is not enough, it can be solved by adding a grinder. It is absolutely not allowed to share a grinder at the same time.
Precautions during the replacement process
(1) Wear problem
Any grinding wheel has its own wear requirements. If the wear is reached to a certain extent, it must be replaced with a new one. It is not necessary to use excessive wear in order to save materials. This is a very unsafe violation. It is generally stipulated that the new grinding wheel should be replaced when the grinding wheel is worn to a diameter 10 mm larger than the diameter of the chuck.
(2) Validity issue
The new grinding wheel that is taken out of the warehouse is not necessarily a qualified grinding wheel. Even the new grinding wheel purchased from the manufacturer is not necessarily a qualified grinding wheel. Any grinding wheel has a certain expiration date and is used within the effective period. It is a qualified grinding wheel; if it is used beyond the expiration date, it is not necessarily a qualified grinding wheel. The regulations stipulate that “the grinding wheel should be used within the validity period. The resin and rubber bond grinding wheel must be subjected to the rotation test after one year of storage. Only qualified persons can use itâ€.
(3) Texture problem
During the use, if any cracks are found in the grinding wheel, stop using it immediately and replace the new grinding wheel to avoid causing the grinding wheel to break and cause injury.
Other precautions
(1) Environmental issues
Grinders should generally be equipped with special grinder rooms, and it is strictly forbidden to stack inflammable and explosive materials near the grinder room or grinder to avoid fire or explosion accidents, and other parts or articles should not be placed near the grinder.
(2) Management issues
The grinder should be specially staffed. If the personnel of the unit are not going to grind the object on the grinder, they must be authorized by the full-time responsible person, and strictly abide by the safe operation rules. It is strictly forbidden to use the grinder without the consent of the responsible person. In addition, the replacement of the grinding wheel should also be carried out by a special person, and it is forbidden for others to replace and install the grinding wheel.
(3) Car closing problem
When the operator stops working, he should immediately turn off the vehicle. It is forbidden to idle the grinder in the absence of use and unmanned management. In addition, the cleaning of the medium and short wave turbines should be maintained after use.
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