What is a bushing
What is a bushing?
Bushing is a supporting part used outside the mechanical parts to achieve the functions of sealing and wear protection. It refers to the ring sleeve acting as a gasket. In the field of valve application, the bushing is in the valve cover. Generally, corrosion-resistant materials such as polytetrafluoroethylene or graphite are used for sealing.
In the moving parts, the parts are worn due to long-term friction. When the clearance between the shaft and the hole is worn to a certain extent, the parts must be replaced. Therefore, the designer selects the materials with low hardness and good wear resistance as the shaft sleeve or bushing in the design, which can reduce the wear of the shaft and seat. When the shaft sleeve or bushing is worn to a certain extent, it can be replaced, In this way, the cost of replacing the shaft or seat can be saved. Generally speaking, the bushing adopts interference fit with the seat and clearance fit with the shaft, because wear can not be avoided anyway, it can only prolong the service life, and the shaft parts are relatively easy to process; Some new designers don’t like this design and think it increases the cost during manufacturing, but after a period of use, it still needs to be transformed according to this method during maintenance, but the transformation is easy to reduce the accuracy of the equipment. The reason is very simple. The secondary processing can’t ensure the supplement of the position of the seat hole center, and the shaft sleeve has a low speed, Places with high radial load and high clearance requirements (such as camshaft) are used to replace rolling bearings (in fact, the shaft sleeve is also a sliding bearing). The material requires low hardness and wear resistance. The inner hole of the shaft sleeve can achieve high matching accuracy after grinding and scraping. There must be oil grooves for lubricating oil on the inner wall. The lubrication of the shaft sleeve is very important. If it is dry ground, the shaft and shaft sleeve will soon be scrapped, It is recommended to scrape the inner hole wall of the shaft sleeve during installation, so that many small pits can be left. The enhanced lubrication bushing and shaft sleeve are selected according to different industrial and mining conditions. The most important conditions are: pressure, velocity, pressure velocity product, lubrication state and load property. The bushing is fast, easy and excellent, and the automatic selection is included.
Wrapped around the valve stem, it is worn and can be replaced easily. If the bushing is not used, replace the parts after wear. Therefore, the bushing is replaced (in design, the hardness of the bushing is reduced to make it a wear part in the friction pair). Because of its convenient processing, low replacement cost and easy replacement. Of course, there are guiding functions, which are second.
Function of bushing
Bushing has high flexibility and can play many roles. Generally speaking, bushing is a kind of component to protect equipment. The use of bushing can reduce the wear, vibration and noise of equipment, and has anti-corrosion effect. The use of bushing can also facilitate the maintenance of mechanical equipment and simplify the structure and manufacturing process of equipment.
The function of bushing in practical work is closely related to its application environment and purpose. In the field of valve application, the bushing is installed in the valve cover to cover the valve stem, so as to reduce the leakage of the valve and achieve the sealing effect. In the field of bearing application, the use of bushing can reduce the wear between bearing and shaft seat and avoid the increase of clearance between shaft and hole.
Material of bushing
The materials of bushings are mostly soft metal, rubber, nylon and non-metallic polymers. These materials have relatively soft texture and low price and cost. In various harsh working environments, the bushing bears vibration, friction and corrosion to protect the wrapped parts, and the bushing itself has the advantages of convenient replacement, low cost and good economy after damage.
Selection factors of bushing
Bushing has a wide range of applications and many types. To select a suitable bushing, we must consider its purpose and select different types of bushings under different working conditions. The main conditions to be considered in the bushing selection are the pressure, speed, pressure speed product and load properties to be borne by the bushing. In addition, whether the bushing is lubricated and the state of lubrication also determines its service effect and service life.
What is an oil-free bushing?
Oil free bushing: also known as self-lubricating bearing, it is a novel lubricating bearing with the characteristics of both metal bearing and oil-free lubrication. It is basically loaded by metal. The solid lubricating material with special formula has the function of air lubrication. It has the characteristics of strong bearing capacity, impact resistance, high temperature resistance and strong self-lubricating ability. It is especially suitable for heavy and low speed, It is also not afraid of the erosion and scouring of water and other acids when it is difficult to lubricate and form oil film, such as reciprocating or swinging.
Main material of oil-free bushing
High copper high strength brass is widely used. It is made into bearing bush and bushing by casting. At present, it is mainly made of high strength brass in China.
Lubricating oil-free bearing (oil-free bearing for short) adopts high-strength brass as the matrix and radially embeds ordered cylindrical polymer fillers as friction materials (generally graphite, molybdenum disulfide, polytetrafluoroethylene, engine oil and other lubricants). Its advantages mainly lie in its complementary advantages of copper alloy and non-metallic wear reducing materials, It not only has high bearing capacity, but also breaks through the boundary that general bearings rely on oil film grease lubrication to realize oil-free lubrication. The embedded solid lubrication is easy to form lubrication film, which has greatly improved its friction and wear performance, stable and reliable, and high cost performance.
High strength brass oil-free bushing product classification:
1. Gasket and sliding plate
2. Square oil-free bushing fixing seat assembly
3. Thrust type, including standard type, cone hollow type and sinking hollow type
4. Flange guide type, effectively ensuring the space on the opposite side.
5. Flange type, including round flange, method flange and opposite flange. The inner diameter tolerance can be F7 and G6, and the outer diameter tolerance is only H7.
6. Shoulder type, anti falling off shoulder type, divided into thick wall and thin wall, tolerance: inner E7 and outer R6.
7. Straight column type, including thick wall type, thin wall type and thick wall type.
Tin bronze: Bronze with tin as the main alloy element. The tin content is generally between 3 ~ 14%, which is mainly used to make elastic components and wear-resistant parts. It has high mechanical properties, wear reduction and corrosion resistance, free cutting, good brazing and welding properties, small shrinkage coefficient and non-magnetic. High strength, corrosion resistance and excellent casting properties have been widely used in various industrial departments for a long time. Tin bronze is the most widely used and consumed in the electrical and electronic industry, accounting for more than half of the total consumption. It is used for various cables and wires, motors and transformers, switches and printed circuit boards. In the manufacturing of machinery and transportation vehicles, it is used to manufacture industrial valves and accessories, instruments, sliding bearings, molds, heat exchangers and pumps.
Tin bronze oil bushing product classification:
1. Shoulder type, anti falling off shoulder type, fixed wall thickness 4mm, tolerance: inner E7, outer R6.
2. Flange type, divided into round flange and opposite flange, inner diameter tolerance: F7, outer diameter tolerance: H7.
3. Straight column type, the most commonly used tin bronze oil-free bushing, temperature resistance: – 30 ~ 150 ℃.
Composite type: it is made by taking steel plate as the matrix, sintering spherical bronze powder in the middle layer and rolling the mixture of polytetrafluoroethylene (PTFE) and lead on the surface layer. It has the advantages of low friction coefficient, wear resistance and corrosion resistance. It is widely used in the sliding parts of various machines, such as printing press, textile machine, hydraulic carrier, tobacco machine, medicinal machinery, fitness device, micro motor, automobile, motorcycle and so on.
Classification of composite oil-free bushing:
1. Flange type oil-free bushing, the flange jacket is made of aluminum alloy, natural color anodizing, and the O-ring is made of nitrile rubber.
2. Straight column type, heat-resistant temperature – 180 ~ 280 ℃.
- 1. Before assembly, ensure that there are no foreign matters on the surface of shaft sleeve and seat hole, and the surface of seat hole shall be as smooth as possible to avoid scratching during assembly.
- 2. During assembly, the outer surface of the shaft sleeve can be properly coated with lubricating oil to facilitate the installation of the shaft sleeve, but it is not easy to be too much, so as to prevent the shaft sleeve from falling off during heavy load or reciprocating motion.
- 3. During assembly, the mandrel shall be pressed in slowly, and it is forbidden for a confidant to knock the shaft sleeve to avoid deformation.
- 4. In order to make the assembly easier and the cutting will not damage the wear-resistant layer, the end face of the shaft must be chamfered and excessively smooth. The material of the shaft is recommended to be bearing steel surface quenching hrc45, the surface roughness is rz2-3, and the surface can be plated with hard chromium.
Features of oil-free bushing:
- 1. Low maintenance frequency;
- 2. Compared with ball type linear bearing, oil-free bushing is suitable for low-speed and heavy-duty occasions;
- 3. It can also be used under severe conditions of high temperature and low temperature;
- 4. Compared with linear bearing, the bushing is thinner and saves space;
- 5. It can be used for both linear motion and rotary motion.
Difference between bushing and shaft sleeve
The shaft sleeve is used on the gear shaft or bearing. Its primary function is to fix and position the water lubricated shaft sleeve. For example, the gear shaft is required when the reducer equipment is used to fix the center positioning of the shaft and the bearing so that it will not be displaced due to the sensation during operation. The shaft sleeve acts as a sliding bearing. In order to save the data of copper based steel ball retainer, the wall thickness of the shaft sleeve is planned according to the axial load required by the bearing. Cast copper and bearing alloy are usually used. The shaft sleeve can be divided into open and non open, which depends on the structural requirements. Usually, the shaft sleeve can not accept axial load, or can only accept small axial load or thrust bearing, and the shaft is usually round.
In some places where the shaft sleeve has low speed, high radial load and high clearance requirements (such as camshaft), the oil free sliding block is used to replace the rolling bearing (originally, the shaft sleeve is also a sliding bearing). The data requirements are low hardness and wear-resistant. The inner hole of the shaft sleeve can achieve high cooperation accuracy after grinding and scraping. There must be oil grooves with smooth oil on the inner wall. The smoothness of the shaft sleeve is very important, Several grinding shafts and shaft sleeves will soon become obsolete. When introducing equipment here, scrape the inner hole wall of the shaft sleeve, so as to leave many small pits and enhance the smooth function.
Bushing is a supporting part used outside mechanical parts to achieve the functions of sealing, wear and maintenance. Bushing has a wide range of applications. Bushing will be used in many parts in the industrial field, such as valves, bearings and other parts. The application flexibility of bushing is relatively high, and it can play many roles. Generally speaking, bushing is a kind of component for equipment maintenance. The application of bushing can reduce the wear, vibration and noise of equipment, and has the effect of anti-corrosion. The application of bushing can also facilitate the repair of mechanical equipment and simplify the structure and manufacturing technology of equipment. In the field of valve application, the bushing is sleeved by the equipment in the valve cover, so as to reduce the leakage of the valve and achieve the sealing effect. In the field of bearing application, the application of bushing can reduce the wear between bearing and shaft seat and avoid the increase of gap between shaft and hole.
The raw materials of the bushing are mostly soft metal, rubber, nylon and non-metallic polymers. The texture of these raw materials is relatively soft and the quotation cost is low. In various harsh working environments, the bushing receives oscillation, conflict and corrosion to maintain the wrapped parts, while the bushing itself has the advantages of convenient replacement after damage, low cost and good economy. The application scope of bushing is large and there are many varieties. To select a suitable bushing, we must consider its application intention and select different types of bushing under different working conditions. The first consideration in bushing selection is the pressure, speed, pressure speed product and load nature to be accepted by the bushing. Whether the bushing is smooth and smooth also determines its application function and service life.
Application and characteristics of copper bushing in mechanical equipment
What are the characteristics of copper bushing?
- 1. Wear resistance: the wear resistance of copper bushing is relatively good, and equipment of different materials have different characteristics. The internal organization of the copper bushing is relatively tight, and there will be no loose phenomenon. It has no pores and trachoma, so the copper bushing looks bright from the appearance, and its color is special. And the most important thing is that its hardness is relatively high.
- 2. Corrosivity: another feature of copper bushing is corrosion resistance and good corrosion performance. It is mainly used in the atmosphere and fresh water, because the environment is relatively good. In the process of using copper bushing, it is generally not easy to bite. The corrosion resistance of copper bushing is mainly reflected in some chemical elements, such as dilute sulfuric acid, hydrochloric acid and fatty acid. Therefore, the corrosion resistance of copper bushing is very good. The reason why it will not bite is mainly due to its own characteristics and good performance, Even if there is no lubricant and water lubricant, it can still work normally, and its sliding performance and self-lubricating performance can still be maintained.
- 3. Compressive capacity: the compressive capacity of copper bushing is also relatively good. Its surface pressure is very large and can well bear the side pressure of bearing. Under high load pressure, copper bushing can also be operated. It is suitable for low-speed and heavy-duty occasions.
What is the role of copper bushing in mechanical equipment?
Copper bushing is widely used in mechanical equipment. Copper shaft sleeve plays many roles in machinery, such as reducing friction, vibration and noise. These are the roles of copper shaft sleeve in machinery. The large copper bushing produced by mining accessories factory is more and more used in the current market, and people also trust it. In the process of mechanical operation, due to the wear of parts caused by long-time friction, copper shaft sleeve is needed at this time. Because it can help reduce friction.
There are many functions of shaft sleeve, which is convenient for people to repair and simplify the structure. In some aspects, copper shaft sleeve can also make up for some mistakes in machine design. Therefore, the shaft sleeve can play a lot of roles. This is its advantage.
How to choose copper bushing?
The application scope of copper bushing is very wide. In the machinery industry, the application of copper bushing is very common. Bearings with different materials have different functions and characteristics. How to select a suitable copper bushing? The following will carefully discuss and explain this problem.
- It has good lubrication function, wear resistance function and corrosion resistance function. It is suitable to use copper bushing as bimetallic forging data. Bearing for vehicle, copper bearing bush of internal combustion engine with peak load of 100MPa, piston pin sleeve, friction plate, etc.
- High strength aluminum brass, high strength in extra brass. Dry bearing with high strength, high hardness, high wear resistance, moderate plasticity and excellent corrosion resistance. Therefore, it is used to forge high load wear-resistant weight on heavy machinery
- Aluminum bronze has high strength, high fineness and stable chemical function. Commonly used in valve body, worm gear, nut, pipe fittings, etc.
- It is a typical Tin Phosphorus Bronze with high hardness and wear resistance. It can be used to make parts subject to severe conflict under heavy load, high speed and high temperature, such as connecting rod bushing, gear, worm gear, etc.
- It can be used to make wear-resistant parts such as bushing, gear, worm gear and so on.
- It has good mechanical function, corrosion resistance, good wear resistance and excellent cutting function.
- Corrosion resistance, especially for dilute sulfuric acid, hydrochloric acid and fatty acids. Structural data, corrosion-resistant and acid resistant accessories, crusher bushing and bearing bush.
- High hardness, high wear resistance, not easy to bite, good forging function and cutting function, excellent corrosion resistance in atmosphere and fresh water.
- Under the condition of short lubricant and water lubricant, it has good sliding and self-lubricating function, easy cutting, poor forging function and good corrosion resistance to dilute sulfuric acid.
Key technology of bushing
- 1. The taper angle difference of the tightening sleeve must be better than that in the national standard, which is expressed by △ D1mp – △ D3mp. The allowable deviation of different size sections is upward from + 0.018-0.09. It is required that the taper angle difference of the tightening sleeve can only be large but not small, that is, the large end must be matched and contacted, the small end of the cone can have a little clearance, and the taper hole is not matched well. The matched self-aligning roller bearing will form a single row of rollers under stress, unstable operation and large vibration, The sound is loud, easy to loosen, and the bearing life is short. The cone angle difference of high-precision tightening sleeve should also be ≤ 0.005 to ensure that the mating contact area is not less than 90%.
- 2. The radial runout (commonly referred to as wall thickness difference) of the outer cone of the tightening bushing facing the inner hole shall be of high precision, otherwise the rotating shaft will have centripetal force due to the fair value, and can not run bumpily, with large vibration and music, and the wall thickness difference of “0”. The maximum value specified in the national standard is about 1/2 of the maximum clearance of the bearing Specification Group in the section below the bearing inner diameter of 65, which is very close to the maximum clearance value of class C precision. Therefore, it is not feasible for the tightening sleeve products qualified in the national standard to be used in the matching of fine grade high load bearings.
- 3. The good straightness of the outer conical surface and inner hole surface of the tightening sleeve means that the form and position tolerance is good and the cylindricity accuracy is good. There is no rule in the national standard. Any single section size is qualified in the tolerance field. In this way, the control of the outer conical surface surface straightness is not strict, especially the grinding of the outer conical surface, the straightness of the blank itself is not good and the grinding wheel correction is not good, The straightness of the appearance is very poor, and ordinary enterprises do not have profilometer inspection. Therefore, this project has great problems in the products of China’s tight sleeve industry, which seriously affects the matching accuracy and stability, and also leads to poor bearing function.
- 4. The supporting bearing of the thread locking function of the locking sleeve is to move and squeeze the end face of the bearing inner sleeve axially through the rotation of the locking nut, so as to tighten the taper between the locking sleeve and the inner hole of the bearing, so as to fix the bearing on the rotating shaft. Therefore, the thread matching between the bearing nut and the locking bushing must be good, which should meet the national standard requirements of ordinary threads.
Application of bushing
Packaging machinery, textile machinery, mining machinery, metallurgical machinery, printing machinery, tobacco machinery, forging machinery, all kinds of machine tools and interchangeable mechanical transmission connection. For example: pulley, sprocket, gear, propeller, large fan and other connections; Features: large torque, high precision, convenient and fast assembly and disassembly, simple operation, good positioning, reducing the scrap rate of matched shaft and hub, reusable and not damaging the matching surface. It is the most ideal and economical choice at present.
- 1. Installation: the bushing has been coated with lubricating oil at the factory and can be directly installed and used. During installation, first screw three bolts into the screw holes of the flange of the other part, evenly distribute them along the circumference, and push the inner sleeve and outer sleeve apart. Then put the expansion sleeve into the hub hole at the design position, and tighten the bolts with a force measuring wrench. The tightening method is that each bolt is only tightened to 1 / 4 of the rated torque each time. The tightening sequence is bounded by the opening, and the left and right cross symmetrically tightened successively to ensure that the rated torque value is reached.
- 2. Disassembly: loosen all bolts for several turns before disassembly. Then screw in the bolt top loose sleeve in the disassembled screw hole crosswise.
- 3. Protection: prevent the expansion sleeve from being polluted during installation. On machines operating in the open air or with poor working environment, the exposed expansion sleeve end face and bolts shall be coated with anti rust grease regularly, and the expansion sleeve type with good anti rust property shall be selected. The expansion coupling sleeve is a new and advanced mechanical basic part in modern times. It is a new type of keyless connection device widely used in the world to realize the connection between parts and shafts, and realize load transmission by tightening grade 12.9 high-strength screws to make the pressure and friction between the inclusion surfaces.
Source: China Bushing Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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