Abstract: In order to overcome the disadvantages such as more extra process time and lower machining precision in current ion beam figuring process mode, which is referred as position mode, a new process mode is proposed, which is referred as velocity mode. The method to determine the feed velocity in velocity mode is discussed in details. To demonstrate the proposed velocity mode process, a  98 flat neoceramic glass sample is figured on the ion beam figuring system KDIFS-500, which is developed by us. Its figure error is improved from initial 33.2 nm root mean square to 3.1 nm root mean square through one figuring process of 17.4 min with convergence ratio reaching 10.7. The figuring result shows that the velocity mode would save process time, improve machining precision and achieve higher convergence ratio than position mode.

Key words: Computer controlled optical surfacing, Dwell time, Ion beam figuring, Optical machining, Velocity mode, Centrifugal compressor Performance Plateau environment Reynolds number Turbocharger