The basics of grinding

the Growth of the productivity and efficiency of modern production steadily requires an increase in speed machining. It is believed that grinding is not a high-speed method, resulting in search of alternatives to the abrasive tool. Increasing the speed of fur.. processing associated with an increase of speed of submission of the instrument, the use of dry processing and wear-resistant tools with a coating of solid materials.
It should be noted that the "abrasive" and "high-speed processing" are not alien to each other concepts. Abrasive wheel usually works with peripheral speed of 30 m/sec.. High-speed grinding wheels of the super-abrasive used in industrial operations at speeds from 75 to 200 m/sec. In laboratory tests with the use of special equipment circles develop a speed of over 300 m/sec, approaching the speed of sound..
Grinding with the use of super-abrasive competes with such activities as : milling, broaching, калевание and in some cases, turning machining of parts high tempering..
Widely applied in the industry of modern materials : ceramics, reinforced metals and polymers, multilayer metals with nonmetallic laminated can often be treated only with the help of grinding.
Grinding circle, representing the abrasive grain in the bundle is capable of самозатачиваться in the process of processing.. When засаливании or затуплении abrasive wheel can be imprisoned or sent directly to the machine, which can not afford any other tool.
Grinding provides tolerance at the surface to hundredths of a millimeter, high-purity processing and a high degree of smoothness..

       the Development of the abrasive industry and improving the processes of grinding associated with the emergence of new abrasive materials.

Types of abrasive materials
       Abrasives are divided into two main groups : conventional abrasives and суперабразивы..
Conventional abrasives are, mainly, the materials of aluminium oxide and silicon carbide, presented in detail in article "Abrasive materials".
Суперабразивы include natural and synthetic diamonds and cubic boron nitride. In comparison with conventional суперабразивы are more expensive, but also more hard and wear-resistant materials.. An important difference of the super-abrasive is their exceptional thermal conductivity (six times теплопроводнее copper), while conventional abrasives, a kind of ceramics, isolated and completely not conduct heat.
Суперабразивы have a high ability to dissipate, which allows them to quickly absorb the heat.. The process of processing суперабразивами can be called - "cold grinding".
As many times harder and tougher conventional abrasives, суперабразивы, however, may not be used without exception in all operations. Each of the types of materials occupies its niche in the mechanical processing..

       Abrasives from aluminum oxide divided into спекаемый (normal) and ceramic aluminum oxide. Ceramic aluminum oxide is produced by atomization of molten alumina and sometimes so call it a "granular"..
Спекаемый aluminum oxide is the most common and inexpensive abrasive used in the grinding of both soft and hard materials, with a small or a large volume of the deleted material in the rough and finishing processing. Well is used for grinding of hardened steels and Nickel-base superalloys..
Ceramic aluminum oxide better used in operations when the load on each grain in the "contact spot" is very high. The most suitable for cylindrical grinding of large surfaces. Not suitable for the operation with a large length of the arc of contact and a small load on the grain, for example for internal and flat grinding.. However, the modified ceramic aluminum oxide is quite suitable for grinding of viscous stainless steel and high-temperature alloys, just at the big length of the arc of contact. (Modified aluminum oxide, obtained by the method of extrusion has a ratio of length to width of grain equal to 5..)

       Abrasives from silicon carbide - this is an extremely acute grain, with an aggressive form. Best suited for grinding of tungsten carbide materials, ceramics. Due to the severity is used for the treatment of soft and fibrous materials, such as brass, bronze, aluminium, plastic, wood, etc..

       Abrasives from natural and synthetic diamonds are not suitable for grinding of steel, but are more suitable for processing of non-ferrous metals and, partially, ceramics..

       Cubic boron nitride (hereinafter - boron nitride), as well as diamonds, is an expensive material, in 50 times greater than the cost of conventional abrasives, but in this case, with more endurance, is capable to process up to 100 times more detail. Tool of boron nitride processing of solid steel with minimal wear and tear.. Is ideal for processing of solid and hardened steels, for example for internal grinding of grooves of the bearings. Retains its shape and rarely requires edits, which is an expensive procedure. Boron nitride reacts with water, and for cooling the better use of the liquid on the basis of glycol or synthetic oil..

Bundle
       Types of chords for conventional abrasives are considered in detail in the article "Types"ligaments, including ceramic, the, смолянистую and flexible ligaments on the basis of polymers.
Tool of super-abrasive is made on спекаемых metal cords and by the application of abrasive coating on the body of a circle on top of Nickel substrate.. To reduce the first variant can be called a bunch of metal, the second - coated. By using both types of ligaments caution should be exercised in the choice of coolant in изибежани hydroplaning.. Excessive hydrodynamic pressure in the contact patch may raise abrasive circle over the treated surface, that leads to a decrease in the quality of processing and premature wear of the circle.

       the Choice of the ligaments always depends on each specific case.. Circles of boron nitride are highly resistant, retain their shape and stretch can stand in the machine to the full depreciation. Taking into account the ability boron nitride have a good heat, the choice of metal bundles to be the most faithful.. Such combination allows to provide the cold grinding branch of the flows of heat from the workpiece grinding grain and the surface of the circle and the cooling of tools fluid.

       Installation of an abrasive tool in the machine. Суперабразивы as on the metal binder, and with coating critical to the beating of the drive spindle.. Spindle backlash should be kept to a minimum, no more than 0.01 mm. The smallest beating especially important for metal binder. Since grain is over a bunch, increased heartbeat, more than 0.02 mm can lead to uneven wear of the circle.
Суперабразивы can not stand the vibration, the errors in the selection and supply of cooling liquid..

       Conventional abrasives on various types of bundles are less critical of the lack of balance of the machine. Especially circles on the elastic tar and elastic cords that can absorb the vibration.
Among conventional abrasives, the most popular circles on vitrified.. Porous ceramic bunch of good delivers the coolant in the contact area of a circle with the workpiece.

Preparation of a circle to work. Edit
       Most of the operations require the preparation of the circle before the beginning of work - dressing.
edit - this обтачивание circle on the periphery of a more solid abrasive.. Conventional abrasives обтачиваются (correct) diamond pencils. Суперабразивы correct электроразрядным method.
Edit circles is at operating speed. Before the beginning of grinding should be given the range of 1-2 minutes rotate freely to warm up the drive mechanism, because of the beating of cold and warm bearings different..
In the edit стачивается a small layer of the periphery of the abrasive wheel.
With the help of edits, first, shall be resolved the green circle on the spindle, the range of центруется, balanced and takes an ideal form in relation to the drive on which it is installed. We can say that the tool is "getting used" to the machine.. Therefore, it is not recommended to move the working circle on another machine, as this will require additional corrections. Usually circle remains in its place to the full depreciation.
Secondly, with the help of grinding give the range of the necessary form (profiling) for grinding of profile products..
In the third, achieve initial roughness of the working side of the circle in accordance with the required purity of grinding.
The processing quality of the abrasive wheel is set by the depth of penetration and the speed of the traverse of the ruling tools (traffic cross the radius of the circle).. Turning the abrasive wheel, like the turning of a pen, made in several stages. First diamond pencil cuts deeply into the body of the circle and move quickly, removing a thick layer of abrasive for its adaptation to the drive. Further, in 5-6 passes with a gradual decrease in the depth of indented and speed of the traverse is given to the necessary roughness..
Edit called the same design circle or sharpening. With the revision range is sharper - diamond removing the specified layer скалывает grinding grain, revealing new cutting the top. The circle is subject to revision as the clogging and blunting of abrasive grains. Clogging is clogging the pores of the circle chips, small particles of dirt.. Treatment restores the cutting ability of abrasive.

Spot of contact
       the Spot of contact - this is a place of contact of a circle with the treated surface. For flat grinding the periphery of the circle spot has rectangular form, the area of which is calculated by multiplying the length of the arc of contact at the height (thickness) of a circle.. In figure 1 the arc of contact made between the points B and C. For example, let's calculate its length.