Types and processing of the hottest coated abrasiv

2022-08-21
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Type and manufacturing treatment of abrasive base material

as one of the three elements of abrasive belt, the base material is the carrier of abrasive belt and adhesive. At the same time, many aspects of abrasive belt characteristics are also reflected by the base material. For example, the flexibility of abrasive belt is transferred from the base material, the size specification also depends on the size of the base material, and the joint form is mainly for the base material. It can be seen that the quality of the substrate will directly affect the processing characteristics and service life of the abrasive belt. From the perspective of the processing process of the abrasive belt, the power required to be transmitted by the substrate will neither stretch nor fracture when it bears the mechanical force in processing and high temperature. This requires that the base material not only have certain tensile strength, shear strength, rupture strength and thermal stability, but also have certain toughness and dimensional accuracy to reduce fatigue damage, impact vibration, etc. in the operation of the abrasive belt. At the same time, because the quality of the base material will be reflected on the surface of the workpiece through abrasive particles. Different substrates, different substrate weaving methods and manufacturers to meet their own needs and even the needs of the world will determine the different properties of substrates and their applications. Substrates are also an extremely important aspect of the research and development of coated abrasive tools

1 Types and applications of base materials

the commonly used base materials include the following categories: paper, rubber film, cloth, vulcanized fiber, polyester fiber and composite base materials. Each base material can be divided into different strength grades according to the required flexibility, strength and material removal rate

paper base material and adhesive film base material

paper has a long history as a base material, with low cost. Its surface is flat and its machined surface roughness is lower than that of cloth base material, but its strength and toughness are poor, and its load capacity is not as good as that of cloth base material. Adhesive film used as a base material is still rare in China. It has been applied abroad (such as Britain) and is one of the development directions of high-precision grinding tools. However, like light load paper, it is often used in light load manual polishing and wood processing due to the limitations of high transmission power and high pressure in rough processing

with the progress of manufacturing technology, people have been able to produce high-strength heavy-duty paper. During the production of heavy-duty paper, polymers are added to further improve its strength. In the past, three or four or more layers of paper can be stacked together to obtain the required strength according to the samples of different widths and sizes, while heavy-duty paper only needs one or two layers to obtain greater strength and less thermal sensitivity. Paper substrate is easy to obtain both in length and width, so paper substrate is more and more popular. The original trial produced annular paper abrasive belt in China can only be used for low load fine grinding or polishing. However, since the introduction of coated abrasive tool production line, paper-based abrasive belts of different specifications and uses can be produced for selection, and the strength is high, but the development of heavy-duty paper is still lacking. However, heavy-duty paper is an important direction of substrate development

in order to improve the strength and flexibility of wet grinding of paper substrate, rubber, resin or other materials are often added or coated in the paper substrate

cloth substrate

is made of cotton or synthetic fiber, and the matrix is soaked with polymers that increase strength. Cotton fabric base is divided into two categories: one is light load fine twill (J) with good flexibility, and the other is heavy load coarse twill (x). Obviously, the coarse twill cloth has high strength and poor flexibility. It is used for grinding on refitted machine tools, as well as for rough machining on disc grinder or belt grinder. When the surface is complex and only needs to maintain its shape, it is more suitable to use non-woven matrix, but the grinding rate is low. Cloth base materials are often divided into four types for selection: J type, X type, Y type and S type. Type J is a light load cloth with soft texture, which is used in rough grinding, forming and polishing: type X cloth base is strong and durable, and is suitable for heavy-duty grinding processing: Type Y cloth is 30% heavier than type X. This heavy-duty cloth base not only has high tensile strength, but also is more resistant to puncture, fracture, wrinkle or disassembly. Facts have proved that it is very suitable for wide abrasive belt grinding of wire and plate. The S-type is cotton fabric, which is used in the combined wide abrasive belt machine

cloth substrates are widely used. Cotton or fiber cloth substrates with polymers have good resistance to various coolants. In high-speed belt grinding, the reasonably selected abrasive particles must match the high-strength substrate. At this time, cloth substrate is often considered

vulcanized fiber substrate

this substrate is laminated by vulcanized fiber. Vulcanized fiber is made from broken cotton cloth and then chemically treated to gelatinize cotton wadding fiber. It is characterized by hard texture, strong strength and good toughness, but it still maintains its flexibility and is insensitive to coolant. The coated abrasive tool made of fiber base material made by overlapping several layers of gelatinized paper, vulcanizing and grinding flat can be used to make grinding discs and roller polishers

polyester fiber substrate

polyester material has many advantages: it has water resistance, and can be widely used in dry grinding, lubricating oil grinding and water cooling grinding without water resistance treatment. Compared with cotton substrate, it has greater tensile strength, rupture strength and shear strength. It can fully meet the requirements of rough machining. It can transmit more than 100kW power during high-speed grinding, and has the ability to buffer and absorb periodic vibration load in time. Table 1 shows the performance comparison of cotton and polyester substrates. Polyester can also form a new composite substrate with cotton fabric or paper. After the emergence of polyester fiber, it has developed rapidly and attracted the attention of belt manufacturers all over the world. It is praised by Norton company of the United States as the top coated abrasive substrate

composite substrate

this is a substrate formed by laminating two or more different substrate materials together. For example, the composite base material of paper and cloth combines the advantages of both. Of course, it is more difficult to manufacture. It can be used in high-speed drum grinder: the composite substrate of vulcanized fiber and cloth is mainly used to make grinding discs: the combined substrate of denir fiber, textile and polyester additives, which is not only stable to a variety of grinding fluids, but also has high toughness and heat insensitivity. This consortium can also achieve different products from soft to hard. The flexible composite substrate can be used in the case that it needs to be suitable for specific shape or soft contact wheel processing; while the harder composite substrate is used for processing hard metal materials or using rubber contact wheels

in addition, some factories have developed fine metal as the substrate of abrasive belt, which can be used in some strong grinding, and the effect is very good. These substrates can be used as cathode in electrolytic abrasive belt grinding and mild steel belt substrate

2 weaving method of substrate

the development of substrate is not only reflected in the progress of substrate materials, but also in the improvement of weaving technology. Different weaving methods make great changes in the properties of the substrate. Figure 1 and Figure 2 respectively show the structural characteristics of the traditional weaving method and the relatively advanced foreign known as e-system weaving method (also known as binding type)

The weaving method of the

e system was introduced in the early 1970s abroad. It marks the beginning of a new generation of substrate that plays an important role in grinding by eliminating it from the following three aspects. The fiber configuration of this unique design is that the strands and ropes are arranged vertically to each other. At their junction, they are bound by other filaments, and the semi-finished products are coated with synthetic resin to improve their tensile strength and heat resistance. Because it does not present a braided state, its length can reach several kilometers, and the continuous strand rope ensures that this substrate has no defects of traditional braided fibers, such as hinge, traction tension, and loose ropes in some places. These defects are difficult to hide in the fatigue life test of various springs, elastomers, elastic components and other parts of the vertical spring change fatigue testing machine produced by Shandong Sida high-tech during fine-grained grinding, so the traditional woven abrasive belt grinding will produce marks when finishing stainless steel or other metals. Moreover, the fiber strands that bear the main load are not crimped and wrinkled, and the friction between the ropes is also reduced. All these make e-system weaving have higher tensile strength, breakage strength, shear strength and deformation resistance. Thus, the service life of abrasive tools can be extended and the service performance can be greatly improved. 3 transfer of flexible substrate mechanical flexibility

coated abrasives are called flexible abrasives, and their flexibility mainly comes from the substrate. Before the manufactured coated abrasive tools are converted into processed products of various specifications, the combination of substrate, binder and abrasive particles is usually hard. In order to make it flexible, it can be wound around a wheel with a small radius for low-speed operation, so that the outermost layer will crack, and the flexibility of the substrate will be transferred to the whole abrasive tools. The crack will make the resin (adhesive) islands and mutually hinged abrasive particles separate at the edge of the crack. Thus, the whole structure of the abrasive tool basically shows the flexibility of the substrate. This process is usually called mechanical flexibility. Although flexible bending may reduce the service life of abrasive tools, the abrasive tools treated with flexible bending are easier to achieve the accuracy required for processing, have lower roughness, and are more stable and reliable in processing operation. When passing through the contact wheel with small curvature, it can prevent irregular fracture or other harmful fracture caused by load. 4. The size and specification of the closed abrasive belt base material of commonly used coating abrasives and the joint

the size and specification of the abrasive belt depend on the base material, because from the manufacturing process of the abrasive belt, there is the base material first and then the abrasive belt. The large roll of sand belt made into various specifications is also mainly tailored for the substrate. The following series can be roughly divided from the width of the sand belt

narrow series abrasive belt: the size width is 6.5 ~ 5mm, and its length can reach several meters. This series of abrasive belt is widely used, mainly used for grinding parts that are difficult to reach, such as scissors, finger holes, medical instruments and small hand tools

medium width series: the size is between 50 ~ 100mm wide, which is commonly used in belt sanders with tensioning seats or hand-held grinding. Typical applications are rough grinding of medical instruments, polishing of turbine blades and golf clubs

heavy duty grinding width series: the size width is 100 ~ 300mm. This kind of abrasive belt requires special fixtures to locate and clamp the workpiece in many applications. Obviously, its application is heavy-duty grinding

wide abrasive belt series: abrasive belts with a size greater than 300mm are often called wide abrasive belts, which are generally used for processing large flat surfaces. Wide sand and the corresponding grinding machine are more difficult to manufacture. In high-speed operation, it is easy to wrinkle and affect the processing quality

the sand belt joint is also for the base material, because the abrasive particles and the binder on the surface of the base material need to be polished off before grinding the edge of the base material joint. The commonly used joint methods include flat joint and lap joint, and the flat joint can be divided into straight edge joint and sine wave edge joint, as shown in Figure 3

The lap joint of

(a) should pay attention to the rotation direction, and the upper edge should be in the direction of grinding, which can make the joint pressurized and conducive to stability. (b) There is a thin and strong polyester film under the flat joint of (b) and (c). This joint is suitable for high-speed grinding, and the rotation direction is not limited. Compared with (b) and (c), the strength (Table 2) and flexibility of sine wave flat joint are better. Because the sine wave substrate itself has mutual clamping effect (c), the right figure has a more uniform stress distribution than the left figure. In a word, the sine wave joint is a more advanced joint form, which is more stable than the straight side flat joint when running, is not easy to show traces, and reduces the common articulation phenomenon in the straight side flat joint. Domestic sand belts usually have two joint forms as shown in Figure 3 (a) (b)

in addition, many special joint methods have been developed abroad, such as welded joint method, spiral joint method and wavy joint method

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