The viscous driven aerostatic supported high-speed spindle

An innovative air driven spindle for micro-milling applications is presented, in which a so-called viscous turbine is used to both drive and support the spindle. The viscous turbine drives the spindle by exerting viscous traction forces directly on the smooth surface of the spindle. It is even possible to use a standard milling tool directly as spindle, thereby rendering a tool holder, with its inherent inaccuracies, redundant. Furthermore the viscous turbine not only drives the tool, but also functions as an aerostatic radial bearing.In this paper the viscous turbine concept is presented, and an optimisation for the pertinent design dimensions is carried out using a simplified analytical model. A prototype spindle design is presented, and the results of the first experiments are analysed and improvements for the second prototype are proposed.