2 Research and development status Previous page Thrust Spherical Roller Bearing
A spherical roller thrust bearing is a rolling-element bearing of thrust type that permits rotation with low friction, and permits angular misalignment. The bearing is designed to take radial loads, and heavy axial loads in one direction.
Spherical roller thrust bearings are of separable construction, The shaft washer is assembled with the cage and a number of asymmetrical spherical rollers and has to be used along with a housing washer having sphered raceway. During mounting, the rings are to be fixed on to their respective seats – shaft washer on the shaft and housing washer on to the housing and then they have to be put together carefully They are manufactured in multiple series. Thrust Spherical Roller Bearing,Single Direction Spherical Roller Thrust Bearing,Thrust Ball Bearings For Detector,Hardness Thrust Spherical Roller Bearings Shijiazhuang Longshu Mechanical & Electrical Equipment Trading Co., Ltd. , https://www.lsjgbearing.com
Shortly after the introduction of the first parallel machine tool in the United States in 1994, people began to study hybrid machine tools. The study of hybrid machine tools abroad is not intended to expand the working space, but from the perspective of obtaining practical machine tool accuracy. This is because the precision and stiffness requirements of the machine tool are much higher than those of the general robot. For example, the motion accuracy requirement is several μm, and the stiffness requires several tens of N/μm or more. Although the theoretical precision and stiffness of the parallel mechanism are high, the actual situation is not as high. For example, the motion accuracy of six-axis parallel machine tools developed by the United States and Japan at that time was several tens of μm, and it could not reach the precision level of traditional machine tools. Although it has been found that the joint structure is a weak link that restricts accuracy, it is very difficult to solve it. Therefore, people began to consider parallel and series use together. In 1997, some hybrid machines were introduced. For example, a three-axis machining center (two-axis parallel, one-axis series) developed by Achen University of Technology in Germany is shown in Fig. 1. Toyota Motor Corporation of Japan has also developed a similar dedicated machining center (two-axis parallel, one-axis series).
Hybrid research and development from the perspective of expanding the work space is also being carried out at the same time. For example, in 1997, we successfully developed a six-axis hybrid CNC machine tool, which uses a three-axis parallel and three-axis series of six-axis hybrid horizontal and horizontal CNC machine tools. The Z-axis feed and the two rotary motions are realized by a three-axis parallel mechanism. The X-axis and Y-axis feeds and the other rotary motion (C-axis for vertical operation and B-axis for horizontal operation) are realized by series drive. Since the rotary motion of the parallel mechanism can reach 90°, the Z-axis can be either vertical or horizontal. The X, Y and B axes (or C axis) are driven in series, and the range of motion can be expanded. The B axis (or C axis) can achieve 360° continuous rotary motion. The five-axis parallel machine tool developed by the Shenyang Institute of Automation in 1999 (actually a hybrid machine tool, four-axis parallel, one-axis series) expands the longitudinal travel range. We are developing a three-axis parallel, three-axis series six-axis hybrid machine (shown in Figure 2), which not only expands the range of three linear motions, but also makes the three rotary motions reach 90°, 90° and 360°. At the IMTS2000 International Machine Tool Show in the United States, the Z3 CNC spindle head used in the Hyper Mach horizontal machining center developed by Cincinnati and DST in Germany is also a hybrid type. It can realize three-axis parallel and two-axis series motion. The three-axis parallel mechanism and the spindle components are composed. In addition to the main motion, the spindle head itself is driven by the parallel mechanism to realize the Z-axis feed and the two rotary feed motions. As shown in Figure 3.
3 Development trends
The hybrid CNC machine tool combines the advantages of the parallel mechanism and the traditional machine tool series. It is a promising CNC machine tool. Although many types of machine tools have been developed, there are still many theoretical and technical problems to be further studied. In order to achieve the theoretical high performance of parallel machine tools, it is more scientific to combine parallel and series to make the machine better. In addition to the theoretical and methodological studies of kinematics and dynamics, the comprehensive technical indicators should further study the basic component technology. Here are a few points.
The innovative design technology of the hybrid machine tool has a lot of room for innovation in the hybrid machine tool solution. Although the method of creating the overall solution of the hybrid machine tool has been studied, many types of hybrid machine tools have been developed, but how to get the best Parallel and series combination, to form a hybrid machine tool program innovation system, there are still many technologies to be further studied.
Joint technology uses a parallel machine tool, and its performance is not up to the theoretical level, the main reason is due to the joint. The problem of joints is mainly the contradiction between structural size, stiffness and precision. In general, the joint stiffness is low. If the pre-tightening method is used to increase the stiffness, the friction will increase, which will lead to a decrease in the motion accuracy. If the rolling bearing with adjustable clearance is used, the outstanding advantage of the parallel mechanism is that the bearing capacity is large, and the current bearing Larger rolling bearing types are also generally larger in size and will result in increased joint size. Therefore, it is a key basic technology to research and develop a high-precision rolling and compact structure with high rigidity and high precision.
The main motor and the electric spindle The spindles of the current hybrid or parallel machine tools are mostly mounted on the moving platform, or driven by the AC servo main motor, or directly by the electric spindle. Since one of the advantages of the parallel mechanism is that the inertia of the moving component is small, the power and torque #weight ratio of the motor are required to be higher, and the vibration and heat generation requirements are more strict.
The adoption of a high-precision detection element parallel mechanism will bring a large number of passive joints. Since the passive joint is not driven by the servo motor, passive joint motion error detection is important whether it is the accuracy calibration of the machine tool or the motion error compensation. This requires research and development of detection elements suitable for passive joint installation, small size, high precision, and strong anti-interference ability.
4 Conclusion
The hybrid machine can combine the advantages of parallel and series, and has good application value. It is a promising type of CNC machine tool. From the technology of the hybrid CNC machine itself, it can be said that domestic and foreign research is almost at the same time. Therefore, we should seize the opportunity, increase the intensity of further research, development and application, and promote the innovation and progress of China's machine tool technology from one aspect, and contribute to the development of China's machine tool industry.
The raceway of the housing washer is at an angle with it`s ais of rotation, so as to be able to allow the rollers to remain in touch with it. As a result, a spherical roller thrust bearing is capable of carrying both a radial as well as an axial load. Spherical roller thrust bearings – because of their internal geometry – are capable of accommodating certain amount of misalignment. However, they can take axial loads only from one direction, and may need to be used in pairs in Back-to-Back or Face-to-Face arrangement, if thrust load from both the directions are to be carried.
Spherical roller thrust bearings are capable of compensating misalignment and shaft deflection.
The bearings are manufactured in normal accuracy. However, bearings with higher running accuracy can also be supplied.
