Observation of Particle Behavior between Tool and Workpiece in Ultra-Precision Local Machining of Glass Surfaces Using Organic Abrasive

Organic abrasive machining (OAM) is a local machining method using organic abrasives and elastic rotating tool with a small-diameter, which is applicable to high-spatial-resolution figure correction of high-precision optical surfaces owing to its low machining rate and small spot size. In order to clarify the machining mechanism of OAM, the particle behavior between the tool and a transparent workpiece was observed in-situ using a microscopic observation system with a high-speed camera. First, the elastic contact area between the tool and workpiece surface was calculated based on Hertzian elastic contact theory, and the tool size for the observation experiment was determined. Next, a microscopic optical system was constructed and the velocity distribution of particles was obtained by in-situ observation. The particles moved linearly along the direction of tool rotation and the speed distribution had a narrow peak width at the center of the contact area. The ratio of particle speed to tool surface speed was independent of the tool rotation conditions (500 rpm to 2000 rpm). The particle speed distribution had a similar profile to the depth distribution of the stationary machining spot.