STUDYING EFFECTIVE FACTORS ON AIR SPINDLE VIBRATIONS USING AIR PAD BEARING IN NANOMACHINING

The increasing demand for precision manufacturing of components for computers, electronics, nuclear energy and defence applications has caused the appearance of ultra precision machining processes. Ultra precision machines are made in order to create very fine and accurate products. The main features of ultra precision machine tools can be classified as: High loop stiffness, high thermal and mechanical stability, low vibration, and high precision axis of motion.
Guide ways, air spindles and drive systems are important parts of ultra precision machine tools. The air spindle is an important element of the ultra precision machine tool, whose vibrations directly affect the quality of the
work surface. In order to achieve nanometer accuracy, the low vibration of the air spindle is vital. Pressurized air is injected into the gap of the spindle in order to make it operative. Some of the parameters affecting air spindle
vibrations are rotational speed, the air compression method, input hole diameter, air pad conditions, and air gap pressure, etc. In this study, the air pad shape, size, depth and number, and rotational speed have been
experimentally investigated. 3 levels are selected for each parameter in experiments. Totally, 243 experiments have been committed. For accomplishing these experiments, air spindles were made using various production processes.
The VibroTest 60 was used for studying air spindle vibrations. Then, experiment results were analyzed by the design of experiment, DOE, method. The results show that the spindles with 2 air pads of 300 mm2 area and 3 mm depth at low rotational speed have minimum vibrations. Also, for air pad shape, circular and rectangular air pads have minimum vibrations.