Key component technology for ultra-precision machining machines (4)

Table 2 Table of various feed mechanism characteristics

5 Environmental conditions

There are three environmental conditions for ultra-Precision Machining. One is pollution. Ultra-precision machine tools must be placed in a clean, clean room to fully exploit their advantages. The cleanliness of the room is expressed in terms of the amount of dust above 0.5 μm in one cubic foot. The working environment of an ultra-precision machining machine should be 20,000 to 3000 or less.

The second is vibration. The disturbance of environmental vibration not only causes the vibration of the machine body, but also causes the relative vibration displacement between the cutting tool and the workpiece. The latter will directly reflect the accuracy and surface quality of the machined part. Therefore, ultra-precision machining machines must be equipped with excellent vibration isolation devices. At present, most of the foreign ultra-precision machining machines use vibration isolation systems with air springs as vibration isolation components, and have achieved good vibration isolation effects. This is mainly because the air spring has a lower bearing capacity while having a higher load carrying capacity. The low stiffness of the spring allows the vibration isolation system to achieve a lower natural frequency, away from environmental interference frequencies, and improve vibration isolation. After theoretical analysis and calculation, the HCM-I ultra-precision machining machine adopts a straight-contracted membrane structure with an internal and external angle of change of 0°. In this way, not only the linearity of the spring stiffness is good, but also the structure is simple, which facilitates the manufacture of the mold and the installation and adjustment of the device.

Table 3 Plan Objectives to Improve Ultra-Precision Machining Accuracy

The third is temperature. The machining of ultra-precision machining machines must be carried out in a constant temperature room. The temperature change during the machining process will cause the machine tool movement accuracy to drop and the specified machining accuracy cannot be obtained. In order to solve this problem, we usually start from two aspects. One is to choose the right part material. The materials used in the ultra-precision machining machine and the candidate materials are alumina ceramic, cast iron, steel, invar, granite, resin concrete and zero. Expanded glass. From the practical point of view, almost all of the HCM-I ultra-precision machine tools use granite. The second is to maintain constant temperature control. After summing up domestic and foreign experience, Harbin Institute of Technology put forward the concept of “effective cold flow rate”. On this basis, the temperature control accuracy of the ultra-precision constant temperature oil supply system has reached the world advanced level.

6 Conclusion

The birth of sub-micron ultra-precision machine tool HCM-I marks that China's ultra-precision machining research has entered the international ranks. However, after all, it has not gone out of the laboratory, there is no commodification, and it is necessary to double the efforts to catch up with the international advanced level. Table 3 lists the accuracy target values ​​of the US POMA and the future accuracy target values ​​considered by Japanese scholars.

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