In mechanical processing, various hydraulic and pneumatic devices are used in both machine tools and auxiliary equipment. With the continuous improvement of the performance of various machine tools and auxiliary equipment, the performance of the supporting hydraulic and pneumatic devices is also required to be improved accordingly, so the technology in this area cannot be ignored.
The hydraulic and pneumatic parts of the main components of the machine tool spindle In recent years, the characteristic of the machine tool is that the structure of the spindle system determines its processing performance, so the performance of the spindle system must be improved. Previously, the performance of various bearings such as sliding, rolling, oil dynamic pressure, oil static pressure, and air static pressure was examined, and the most suitable application was determined according to the characteristics of each bearing. However, because the spindle system has very strict requirements on bearings, it is difficult to determine the selection benchmark from the above evaluation. In the 1970s, hybrid bearings combining oil static pressure and air static pressure have attracted great interest as main bearings, but today, this representative bearing should be further explored.
Now, in some high-speed machining centers, aerostatic bearings are used as spindle bearings, which indeed show the advantages of high rotation precision, small thermal deformation, suitable for high-speed rotation and low noise, and found that as long as the rigidity and High-speed processing of difficult-to-cut materials can be performed by increasing the power of the machine tool. But in the past, it was only a low-rigidity, ultra-precision machining spindle bearing, suitable for cutting soft metals with diamond tools. In addition, magnetic spindle bearings that have the same principle as aerostatic spindle bearings without solid contact have also begun to be popularized. Due to the high price, it is only used in some ultra-high-speed grinding machines at present. It is expected that after solving problems such as vibration, rigidity and thermal deformation in the future, it will be used in ultra-high-speed rotary spindles with a dn value (spindle diameter d×spindle number of revolutions n) exceeding the limit of rolling bearing rotations exceeding 4 million.
Now a hydrostatic spindle bearing has been developed, which is characterized by low viscosity, high heat capacity, high load capacity and good adaptability to environmental protection. It is expected to be put into actual production use in the near future, giving users more choices.
With the development of hybrid bearing technology in the spindle system, in order to implement high-speed and high-rigidity guidance on the workpiece at the same time, the semi-floating guidance that combines sliding, air and oil static pressure is now adopted.
Regarding the driving method of the workbench, although there are ultra-precision machine tools driven by transmission shafts, the screw drive with ball wires still accounts for the majority. In the positioning work to achieve special purposes such as X-ray exposure devices, the newly developed static pressure air screw drive has begun to be applied. Although its price limits its scope of use, it will be widely used in the ultra-precision field.
In order to make the currently used linear motor achieve the goal of small thermal deformation and good rigidity, so as to ensure the positioning accuracy of the workbench to the level of nm level, after considering the application of electroviscous fluid, the viscosity can be continuously changed according to the load and speed, so that The purpose of controlling the positioning of the workbench very precisely is achieved.
The unclamping device has realized high-speed rotation speed of the machine tool and feed speed of the tool in order to improve production efficiency, and the clamping of the workpiece has also been automated. But in the past, most of the clamping devices in medium and small NC machine tools were clamped by oil pressure. 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 hydraulic transmissions that will not pollute the environment.
In addition, opportunities to utilize air pressure are increasing to meet the needs of unmanned operation of machine tools. If a large-capacity air compressor is installed separately, it will not only expand the installation area of the equipment, but also the utilization rate is not high. Developed a kind of device that air compressor and accumulator are arranged simultaneously in hydraulic device for this reason now. Because it can be supplied with oil pressure and air pressure by an electric motor, it not only improves the utilization rate of the equipment, but also saves the space for installing the equipment, which is an excellent design.
