The development trend of machine tools

　　 Machine tools are currently changing in several major directions, first of all, the increase in the application of 5-axis processing machines and compound processing machines. 5-axis processing machines and composite processing machines began to appear in the market around the second half of 1990, and have now been widely used in the market. They are characterized by the addition of grinding processing, inspection, and workpiece handling robots in addition to cutting processing. In addition, there is a trend to further increase the number of control axes, which is a tendency to become more complex. The second is that the machine tool has become easier to operate. For example, the function of automatically correcting the mechanical thermal displacement during processing is set in the machine tool; the function of checking the interference between the abrasive and the workpiece; the function of monitoring the status of the spindle in operation (involving temperature, vibration, displacement, etc.); and the intelligence of the equipment change. These changes will make the machine tool easier to operate. Then there is the development of machine tools to high-precision, micro-machining. This improves the performance of components such as DD motors or linear motors, and makes it possible to determine the position accuracy of the sub-precision level. The other is that the machine tool has become more space-saving. At present, there is also a significant demand for high-performance compact machines in mass production lines. In order to suppress the width of the equipment more and improve its maintainability, a 5-axis processing machine with a equipment width of 1000 mm has been launched. The last point is that machine tools are developing in the direction of reducing environmental load. With the reduction of the air flow rate of oil-air lubrication and the switch from oil-air lubrication to grease lubrication, many machine tools designed to be aware of environmental issues have appeared on the market.

Technical trends of bearings for spindles

　　1. The coexistence of high speed and high rigidity

　　 In the context of the development of machine tools to complex, This tendency to produce more varieties and less batches, change varieties to batch production, and the total number of projects has become even higher. The processing of multiple workpieces on multiple machines is combined into one machine tool, or multiple processes such as rough machining and finishing are combined into a few projects to contribute to improving production performance and saving space. Therefore, for machine tool spindles, there is a need to develop a wide range of machining from low-speed rotating heavy cutting to high-speed rotating light cutting. As a bearing, the coexistence of high speed and high rigidity is required. For high speed, the single dmn value of the bearing (P.C.D.×rotation speed of the bearing) realizes an angular contact ball bearing of 4 to 5 million and a cylindrical roller bearing of 2 to 3 million, which meets the requirements of machine tools. However, attaching importance to high speed is disadvantageous to rigidity. For this reason, in the design of the spindle, there are many cases where high speed and high rigidity have to be emphasized at the same time. It can also be seen from this that maintaining high speed and having the necessary rigidity on the heavy cutting side is a subject for future bearing development.

　　2. New lubrication method

　　Lubrication is roughly divided into oil lubrication and grease lubrication. Generally, oil lubrication is used where high-speed machining is important, and grease lubrication is used where low-speed rotation and cost, usability, and reduction of environmental load are important. However, with the advancement of machine tools, it is hoped that there will be a lubrication method that can satisfy both processing occasions at the same time.

　　As a bearing manufacturer, oil lubrication is improved to maintain high-speed machining while saving energy and improving environmental performance, or the development of technology to improve grease lubrication is underway. In other words, lubrication technology is an element that has a great influence on bearing performance, and there are many issues that need to be developed in the future.

　　3. Bearing design

　　 Bearings for machine tool spindles, according to various requirements such as high speed, high rigidity, and reduced environmental load, users can choose the most suitable model according to their needs. The main dimensions of each bearing are in accordance with ISO standards, and the minimum design changes to the shaft or housing can replace past products and improve the performance of existing equipment.