The performance of rolling bearings directly affects the overall performance of the machine tool Shanghai giant Bearing Co., Ltd.2020-04-06 18:15:50
Today, the market demand for machine tools supporting efficient production systems is becoming more and more complex. Rolling bearing, hereinafter referred to as bearing, is a rotating part of machine tool, and it is a component that can not be ignored. Its performance directly affects the performance of machine tools. Development trend tools for machine tools The machine tools are changing in several main directions at present.The first is to increase the use of 5 axis machine tools and compound machine tools. The five axis machining and compound processing machine began to appear in the market in the second half of 1990, and has been widely used in the market.They are characterized by increased grinding, inspection and workpiece handling robot functions. In addition, the trend now is to further increase the number of control axes, which is a more complicated trend. Second, the machine tool becomes easier to operate. For example, in machine tools, the thermal displacement function of machine tools is automatically corrected in the processing process; the function of interference between grinding tools and workpiece is checked; the function of spindle state in monitoring operation involves temperature, vibration, displacement and so on. These changes will make the machine tool easier to operate. Then the development of machine tools, in order to achieve high precision and precision processing. In this way, the performance of DD motor and linear motor can be improved, and the precision of sub precision position can be determined. In addition, the machine tool becomes more economical. At present, high performance requirements for compact machines in large-scale production lines are also important.In order to further inhibit the width of the device and improve its maintainability, a 5 axis machine with a width of 1000 mm has been released. The last point is that the machine tool is developing towards reducing the environmental load. The reduction of air and air lubricated air flow and the conversion from air air lubrication to grease lubrication have resulted in many machine tools designed by the market to be aware of environmental problems. Technology trend spindle bearings 1.Coexistence of high speed and high rigidity Under the background of the development of compound machine tools, this multi variety, small batch production, multi variety to multi output trend production, and total engineering has become higher. Multiple jobs processed on multiple machines are merged into one machine, or multiple processes such as rough machining and finishing machining are combined into several projects to improve production performance and save space. Therefore, for machine tool spindles, a wide range of machining ranges from low speed rotary heavy cutting to high speed rotary light cutting is needed.As bearings, high speed and high rigidity are required. For high-speed, the single DMN value of the bearing.The speed reached 4 to 5 million angular contact ball bearings and 2 to 3 million cylindrical roller bearings, meeting the requirements of machine tools. However, if we emphasize the high speed, we will damage the rigidity. For this reason, the design of the spindle often must consider both high speed and high rigidity. It can be seen from this point that keeping the high speed and having the necessary rigidity on the heavy cutting side is the theme of future bearing development. 2.New lubrication method Lubrication is broadly divided into oil lubrication and grease lubrication. Oil lubrication is usually used in areas where high speed machining is needed, while rotating at low speed is very important and reduces cost. Grease is used in usability and environmental loading. but With the development of machine tools, people hope to have a lubrication method that can meet two processing occasions simultaneously. As a bearing manufacturer, the improvement of oil lubrication can save energy and improve environmental performance while maintaining high speed machining, or is developing lubricating grease lubrication technology. In other words, lubrication technology has great influence on bearing performance. There are still many problems to be developed in the future. 3.Bearing design According to various requirements of high speed, high rigidity and environmental load reduction, the four types of high performance angular contact ball bearings R, C, D and F are available. R ball diameter has a large number of balls, which is a rigid design.The C ball has a large diameter and uses ceramic balls. This is a design that emphasizes life. Considering centrifugal force, it is more suitable for high-speed design than type D. Users can choose the most suitable model according to their needs.The main dimensions of each bearing conform to the ISO standard.The minimum design change of the shaft or bearing housing can replace the previous product, and can also improve the performance of the existing equipment accordingly. Compared with the original high speed bearing ACH series, the high speed limit of the speed bearing is about 1.3 times that of the original bearing, and the temperature rise is reduced by 20 to 30.R bearing uses ceramic material as rolling element, type C. The bearing has the same tendency as the original bearing, so it is possible to choose the R type design with emphasis on rigidity and the C design with emphasis on load capacity according to the speed of use. According to the high speed performance of high performance bearings and the influence of temperature rise, high speed rotary spindle can also adopt high-precision positioning preload. Under the condition of grease lubrication, the comparison between the rolling bearing ceramic and oil lubricated R bearings and the original bearing's heating characteristics shows that the high performance bearings have been identified as grease - which can be lubricated in the areas where the original bearings need oil air lubrication, thus preventing the environmental impact caused by the oil dispersion and the cost reduction due to the use of lubricating devices.。 As for the R type, the sub ring type with proper amount of grease has gradually increased the standard. These R and C bearings and original bearings also have standard types that can be grease lubricated or lubricated.But they can be used at a higher speed.There are two types of oil and gas lubrication: D and F. The shape of the bearing is derived from the influence of the wind barrier when these bearings rotate at high speed. D bearing and R bearing ball are ceramics. The D type bearings have been confirmed to have high speed performance of about 1.1 times of R bearing, and the temperature is reduced by 5 to 10.To the inner ring of the D bearing. From the side grooves to the oil and gas lubrication of the guide rail is supplied directly and is not susceptible to windshield.Compared with the original lubrication, the air flow can be reduced by 20.In addition, the wind noise generated by the ball can be reduced. Through these good functions, it will contribute more to energy saving or noise reduction. F bearing is original. The oil filling area is installed on the side of the bearing, and the ultra-high speed rotating bearing supplies oil and gas from the oil injection nozzles on the outer ring to the guide surface of the cage. In fast acceleration or deceleration or ultra high speed rotation, the sliding contact of the cage guide surface may be unstable. However, oil and natural gas can be supplied from the nozzle of the outer ring to stabilize the cage operation. Compared with the current high performance cylindrical roller bearings, the high speed performance can be increased by about 1.5 times and the temperature rise is reduced by about 15. The advantages of high speed cylindrical roller bearings make the structure of the spindle simple.Usually, the supporting structure on the rear side of the spindle must be able to absorb the expansion and contraction of the shaft caused by temperature changes. Although cylindrical roller bearings are suitable for this function, the structure of angular contact ball bearings and auxiliary bearing blocks is usually used as a support because of the fact that high-speed rolling bearings have not yet reached the reality.Rear side of high speed spindle However, because the new high-performance cylindrical roller bearings developed can also be used together with the high-speed spindle, the structure around the bearing can be greatly simplified. The existing high-performance cylindrical roller bearings will cause damage to the cage when rotating at high speed, which limits its high speed performance. But if we improve this shortcoming, we can further improve the high speed performance. First, the material of the cage is lighter than the original polyamide resin and is suitable for high-speed rotation.High strength resin improves strength. In addition, when rotating at high speed, the contact part of the cage and roller becomes a neck structure, so that the contact shape of the roller in the cage cavity is optimized, and the friction is reduced and low.The temperature rise was realized. In addition, the ring material is the same as the original product, uses the easy to start bearing steel, and improves the high speed performance through the internal design suitable for high-speed rotation. 4.High reliability In order to improve the reliability of machine tools, the reliability of bearings must be improved. For this reason, the life of the bearing is determined by the temperature or vibration of the bearing. Therefore, prediction technology is essential. In addition, if the load on the bearing can be detected, the most suitable pre load and lubrication can be self controlled according to the machining state.As a result, high speed performance, high rigidity and wide width correspondence are possible in the processing area. Based on this, the development of a unique mechanism has been developed by the Czech Republic, and the most suitable preload can be applied to the bearing according to the speed.From low speed to high speed, the mechanism can be sufficiently rigid.The combination of high output and built-in motors can make high load handling more effective. Conduct. With the initial positioning pretightening method, the spindle stiffness increases with the increase of speed, but with this mechanism, especially when the torque is high, the spindle stiffness of the low speed rotating area will increase sharply, which is suitable for high load machining. Way.