Study of Dynamic Characteristics and Design Analysis of Bush&Spindle of Ultra-Precision Aerostatic Bearing

Aerostatic bearings have been adapted to develop spindles called ultra precision aerostatic spindles. Since most of the ultra precision machines require precision class spindle with higher running accuracy, stiffness and good thermal stability. Aerostatic bearings are in greater demand. Aerostatic bearing gives high rotational accuracy, thermal stability, stiffness and high operating speeds, compared to other types of bearings. Ultra-precision machines require spindles with nanometer accuracy in rotation, moderate axial and radial stiffness, and moderate load carrying capacity. Later various concepts like active air bearings and passive air bearings and others were developed. Accompanying this, further high precision is demanded for spindles and spindle supporting bearings that are elements of machine tools. In the present work an attempt has been made to develop an aerostatic spindle for ultra-precision machine tool which overcomes the drawbacks present in anti-friction bearing spindle which were used in precision machine tools. As problems like wear, thermal errors, lubrication problems, bearing failure, etc, were encountered in anti-friction bearings there was a serious research in the field of precision engineering. Different types of aerostatic bearings are analyzed and the best one is selected for design and further development. Detailed design of axial grooved journal bearings is done and groove parameters are studied and optimized. Then the concept of using aerostatic bearings was developed and it received a huge response from all organizations and research centers.