How to choose coupling

this process contains many different performance factors, including torque, shaft deviation, hardness, speed, space requirements, etc. The coupling needs to meet all these factors in order to make the system run normally. Before choosing couplings, we need to know the performance and application of these couplings in detail. Different types of couplings have their own advantages and disadvantages. The purpose of this paper is to introduce the application of different types of couplings in various servo systems to the end users of servo couplings, and to help the end users point out the factors to be considered in the design and manufacturing process and how to effectively connect different products to correctly select the appropriate couplings. Choosing suitable servo coupling is an important part of the whole system design, which will greatly affect the overall performance of the system. For this reason, the coupling should be considered as early as possible in the design process, and the functional objectives of various couplings and the system should be arranged and compared respectively, so as to avoid the problems that often occur in the practical application of motion control. Each of the couplings discussed above has its own characteristics, which makes it suitable for various applications. However, a single kind of coupling can't adapt to every application field. This makes there are various kinds of couplings on the market at present, so that the design engineer can choose the most suitable coupling to optimize the performance of the system and have a long service life. In addition to the five kinds of elastic coupling, slider coupling, plum coupling, bellows coupling and diaphragm coupling mentioned in the article, there are also shaft sleeves and rigid couplings. Every product of the giant company uses special steps in the production process to ensure its highest performance level and beautiful appearance. For the convenience of reading, this paper is divided into six parts, describing the characteristics of various couplings in detail, hoping to provide you with some help. Elastic coupling elastic coupling is usually made of metal round bar by wire cutting, and the commonly used materials are aluminum alloy, stainless steel and engineering plastic. Elastic coupling uses parallel or spiral grooving system to adapt to various deviations and accurately transmit torque. Elastic coupling usually has good performance and price advantage. In many practical applications of stepping and servo systems, elastic coupling is the first choice. The integrated design makes the elastic coupling realize the advantages of transmitting torque with zero clearance and no maintenance. There are two basic series of elastic couplings: spiral groove type and parallel groove type. The spiral groove elastic coupling has a continuous multi-turn long slot, which has excellent elasticity and small bearing load. It can bear all kinds of deviations, and is most suitable for correcting deviation angle and axial deviation, but its ability to deal with eccentricity is poor, because bending the spiral groove in two different directions at the same time will produce great internal pressure, which will lead to premature damage of the coupling. Although the long spiral groove coupling can be easily bent under various deviations, it also has the same influence on the stiffness of the coupling under torsional load. Excessive slewing clearance under torsional load will affect the accuracy of coupling and weaken its overall performance. Spiral groove elastic coupling is an economical choice, which is most suitable for low torque applications, especially in connecting encoders and other light instruments. Parallel groove elastic coupling usually has 3-5 slots to deal with the problem of low torque rigidity. The parallel groove type takes into account the shortening of the groove without weakening the ability to bear the deviation correction. The short groove can enhance the torque rigidity of the coupling and overlap it, so that it can bear considerable torque. This performance makes it suitable for light load applications. For example, the connection between servo motor and ball screw. However, this performance will increase the bearing load with the increase of slot size, but in most cases, it can effectively protect the bearing. Increasing the size means increasing the ability to bear eccentricity. At present, most elastic couplings are made of aluminum alloy, and Guangzhou Juren Automation Equipment Co., Ltd. also provides elastic couplings made of stainless steel. In addition to corrosion resistance, stainless steel elastic coupling also increases the torque bearing capacity and rigidity, which can even reach twice that of similar products made of aluminum alloy. However, this increased torque and rigidity will be offset by increased mass and inertia to some extent. Sometimes the negative effects will outweigh its advantages, which makes users have to find other forms of couplings. Sliding block coupling The sliding block coupling is composed of two shaft sleeves and a central sliding block. As a torque transmission element, the center slider is usually made of engineering plastics, and other materials, such as metal materials, can be selected under special circumstances. The center slider passes through both sides at 9? The oppositely distributed clamping grooves are connected with the shaft sleeves on both sides, so as to achieve the purpose of transmitting torque. The center slider and the shaft sleeve are matched with tiny pressure, which can make the coupling run with zero clearance in the operation of the equipment. With the increase of service time, the slider may lose its function of no recoil due to wear, but the center slider is not expensive and easy to replace, and its original performance can still be exerted after replacement. The slider coupling is commonly used in general motors, and can also be used to connect servo motors in some occasions. In the process of use, the relative displacement is corrected by the sliding of the central slider. Because it is the friction between the slider and the shaft sleeve that resists the relative displacement, the bearing load between them will not increase because of the increase of the relative displacement. Unlike other couplings, the slider coupling has no elastic element that can work like a spring, so the bearing load will not increase because of the increase of relative displacement between shafts. In any case, this series of couplings is more cost-effective, and the biggest advantage of this kind of coupling is that it can choose sliders of different materials. Guangzhou Juren Automation Equipment Co., Ltd. can provide a variety of raw material center sliders to adapt to different applications according to the specific requirements of customers. Generally speaking, one kind of material is suitable for zero clearance, high torque rigidity and high torque, and the other kind of material is suitable for low-precision positioning without zero clearance, but it has the function of absorbing vibration and reducing noise. Non-metallic sliders also have excellent electrical insulation and can be used as mechanical fuses. When the slide block of engineering plastics is damaged, the transmission function will be completely terminated, thus protecting valuable mechanical parts. This design is suitable for large parallel relative displacement. The split three-part design of slider coupling limits its ability to compensate axial deviation, for example, it cannot be used in push-pull applications. At the same time, because the central slider is floating, the two-axis movement must ensure that the slider will not fall off. There are two main types of plum blossom coupling, one is the traditional straight claw type, and the other is the curved (concave) claw type zero clearance coupling. The traditional straight-claw quincunx coupling is not suitable for high-precision servo drive applications. The zero-gap claw-type plum blossom coupling is evolved from the straight claw type, but the difference is that its design can be suitable for the application of servo system, and it is often used to connect servo motors, stepping motors and ball screws. The purpose of curved surface is to reduce the deformation of elastic quincunx spacer and limit the influence of centripetal force on it at high speed. Zero-clearance claw coupling is composed of two metal shaft sleeves (usually made of aluminum alloy, stainless steel can also be provided) and a plum blossom elastic spacer. The plum blossom elastic spacer has several blade branches, just like the slider coupling, it also matches the plum blossom elastic spacer with the shaft sleeves on both sides by pressing, thus ensuring its zero clearance performance. Different from the slider coupling, the plum blossom coupling is driven by squeezing, while the slider coupling is driven by shearing force. When using claw coupling with zero clearance, users must be careful not to exceed the maximum bearing capacity of elastic elements given by the manufacturer (on the premise of ensuring zero clearance), otherwise the plum blossom elastic spacer will be crushed and deformed to lose elasticity, and the preload will disappear, resulting in the loss of zero clearance performance, which may be discovered by users only after serious problems occur. The quincunx coupling has a good balance performance and is suitable for high-speed applications (the highest speed can reach 3, rpm), but it cannot handle large deviations, especially axial deviations. Larger eccentricity and deflection angle will produce larger bearing load than other servo couplings. Another concern is the failure of the quincunx coupling. Once the quincunx elastic spacer is damaged or fails, the torque transmission will not be interrupted, and the metal claws of the two bushings mesh together to continue to transmit torque, which is likely to lead to system problems. Choosing the appropriate plum blossom elastic spacer material according to the actual application is a great advantage of this coupling. Guangzhou Juren Automation Equipment Co., Ltd. can provide plum blossom spacers of various elastic materials with different hardness and temperature tolerance, so that customers can choose the appropriate materials to meet the performance standards of practical application. Diaphragm coupling Diaphragm coupling consists of at least one diaphragm and two shaft sleeves. The diaphragm is fastened to the shaft sleeve with a pin, which generally does not loosen or cause backlash between the diaphragm and the shaft sleeve. Some manufacturers provide two diaphragms or three diaphragms, with one or two rigid elements in the middle and two sides connected to the shaft sleeve. The difference between single diaphragm coupling and double diaphragm coupling is the different ability to deal with all kinds of deviations. In view of its complicated bending of diaphragm, single diaphragm coupling is not suitable for eccentricity. The double diaphragm coupling can bend in different directions at the same time to compensate for eccentricity. This characteristic of diaphragm coupling is a bit like bellows coupling. In fact, the coupling transmits torque in the same way. The diaphragm itself is very thin, so it is easy to bend when the relative displacement load is generated, so it can bear the deviation as high as 1.5 degrees, and at the same time produce lower bearing load in the servo system. Diaphragm coupling is often used in servo system. Diaphragm has good torque rigidity, but it is slightly inferior to bellows coupling. On the other hand, the diaphragm coupling is very delicate, and it is easy to be damaged if it is misused or improperly installed in use. Therefore, it is necessary to ensure that the deviation is within the tolerance range of the normal operation of the coupling. Choosing a suitable coupling is a key step to make good use of the coupling. In the design stage, you have to consider what type of coupling to choose. Guangzhou Juren Automation Equipment Co., Ltd. can provide you with relevant consulting services. Bellows coupling Bellows coupling consists of two shaft sleeves and a thin-walled metal tube, which are usually connected by welding or bonding. Although many other materials are available, the most commonly used materials are stainless steel metal tube materials and aluminum alloy shaft sleeves. Stainless steel bellows has excellent rigidity and strength, and is often manufactured by hydraulic shaping. Hydroreforming is to put the thin-walled tube on the machine and use hydraulic pressure and special fixture to shape it. The characteristics of this bellows make it an ideal component for motion control. A thin and uniform metal tube can be easily bent when it is subjected to load caused by three basic deviations between axes, namely axial deviation, eccentricity and deflection angle. Under normal circumstances, bellows coupling can withstand 1? －2? Angle, eccentricity of .1 mm-.2 mm and axial deviation of-1.5 mm-+.7 mm.. The thin and uniform pipe wall of corrugated pipe coupling makes it produce very low bearing load, and keeps the constant rotation of each point, instead of destroying the high load point and low load point of circulation like other couplings, and keeps rigidity when bearing torque load. Torque rigidity is the main factor that determines the accuracy of coupling. The better the rigidity, the higher the transmission accuracy. Among the couplings suitable for servo system applications, bellows coupling is the best in rigidity and the most ideal coupling for high precision and high repeatability applications. For corrosive occasions, Guangzhou Juren Automation Equipment Co., Ltd. can provide bellows couplings with stainless steel sleeves, but this increases the weight and reduces the performance advantages of this coupling. The low inertia of bellows coupling using aluminum alloy shaft sleeve in practical application is a very important performance in today's rapid response system. Rigid coupling Rigid coupling, as its name implies, is actually a kind of torsional rigid coupling. Even under load, there is no turning gap. Even when there is a deviation to produce load, the rigid coupling still transmits torque rigidly. If there is any deviation in the system, the shaft, bearing or coupling will be damaged prematurely, that is to say, it can not be used in high-speed environment because it can not compensate the relative displacement between shafts caused by high temperature caused by high-speed operation. Of course, if the relative displacement can be successfully controlled, the rigid coupling can also play an excellent role in the application of servo system. In particular, the small-sized rigid coupling has the advantages of light weight, ultra-low inertia and high sensitivity, and in practical application, the rigid coupling has the advantages of maintenance-free, super oil resistance and corrosion resistance. Although people disapproved of using rigid coupling in servo drive in the past, recently, due to its high torque tolerance, rigidity and zero clearance performance, aluminum alloy rigid coupling with small specifications has been more and more used in the field of motion control.