Hydraulic and pneumatic devices are used in machine tools and accessories. With the continuous improvement of the performances of various deep hole drilling machines and auxiliary equipment, the performances of hydraulic and pneumatic devices required to be matched are also improved accordingly, so this technology can not be ignored.
In recent years, the main components of machine tools are hydraulic and pneumatic spindles. The main characteristics of machine tools are that the structure of the spindle system determines its processing performance. Therefore, the performance of the spindle system must be improved. Previously, the performances of various bearings, such as sliding, rolling, hydrodynamic, hydrostatic and aerostatic, have been examined, and their most suitable uses have been determined according to their characteristics. However, due to the strict requirements of the main shaft system on bearings, it is difficult to determine the selection criteria from the above evaluation. In the 1970s, hybrid bearings combined with hydrostatic bearings and aerostatic bearings had aroused great interest as main bearings, but today the representative bearings should be further discussed.
Now, aerostatic bearing is used as spindle bearing in high-speed machining center, which shows the advantages of high rotary accuracy, small thermal deformation, suitable for high-speed rotation and low noise. It is also found that high-speed machining of difficult-to-cut materials can be carried out by improving rigidity and increasing the power of machine tools. But in the past, it was only a spindle bearing used for low rigidity and ultra-precision machining. It was suitable for cutting soft metals with diamond tools. In addition, magnetic spindle bearings, which have the same principle as air hydrostatic spindle bearings and do not occur solid contact, have also begun to be popularized and applied. Because of the high price, it is only used in some super high speed grinders. It is anticipated that after solving the problems of vibration, rigidity and thermal deformation in the future, it will be used in ultra-high speed spindles whose d n value exceeds the rotation limit of rolling bearings (spindle diameter d * spindle rotation number n) exceeding 4 million
Now a hydrostatic spindle bearing has been developed. Its characteristics are low viscosity, high heat capacity, high load capacity and good adaptability to environmental protection. It is expected that it will be put into practical production in the near future, so that users can have more choices.
With the development of hybrid bearing technology in spindle system, in order to implement high-speed and high-rigidity alignment for workpiece at the same time, semi-floating alignment with sliding, air and hydrostatic pressure is adopted now.
As for the drive mode of the worktable, although there are ultra-precision machine tools driven by transmission shaft, the threaded drive with ball screw still accounts for the majority. In the positioning work of X-ray exposure devices and other devices for special purposes, the newly developed static pressure air screw driver has been applied. Although its price limits its scope of application, it will be widely used in ultra-precision field
In order to achieve the goal of small thermal deformation and good rigidity of the linear motor currently used so as to ensure that the positioning accuracy of the worktable reaches the level of nms, after considering the application of electric viscous fluid, the viscous continuously changes according to the load and speed, so as to achieve the purpose of controlling the positioning of the worktable very accurately.
In order to improve production efficiency, the clamping device has realized high speed in machine tool return speed and tool feed speed, and the clamping of workpiece has also realized automation. But in the past, the clamping devices of medium and small NC machine tools were mostly operated by oil pressure clamping. Now, in order to meet the needs of environmental protection, it is gradually replaced by electric motors, cams and threads. At the same time, it is also developing miniaturized oil hydraulic transmission devices that will not pollute the environment.
In addition, in order to meet the needs of unmanned operation of machine tools, the opportunities of utilizing air pressure are increasing. If a large capacity air compressor is installed separately, not only the installation area of the equipment should be enlarged, but also the utilization rate is not high. For this reason, a device with air compressor and accumulator in the oil pressure device is developed. Because it can supply oil pressure and air pressure by a motor, it not only improves the utilization rate of equipment, but also saves the site to install equipment. It is an excellent design.