Development of an ultra-precision grinding system for machining optical aspheric components with a large depth-diameter ratio

When grinding a large depth-diameter ratio aspheric part of high precision and high quality, the factors influencing surface roughness and profile accuracy of machined surfaces were theoretically analysed first. Afterwards the authors designed and manufactured the ultra-precision aspheric grinding system. The workpiece spindle, transverse guideway, longitudinal guideway and the grinder spindle are in aerostatic form. Turning accuracy of the workpiece spindle is 0.05 mum, the maximum rotational speed of the grinder is 80 000 r/min and the turning accuracy is 0.1 mum, and the resolution of linear displacement of the transverse and longitudinal guideway is 4.9 nm. The accuracy of the precise adjusting mechanism is 0.1 mum. The discharge principle of the dressing mechanism was developed in order to dress the diamond wheel. The ball-headed wheel has high profile accuracy after dressing. This mechanism solved the problem of on-position dressing of the case iron bonded diamond wheels and reduced the machining errors for aspheric surface components. Finally, grinding experiments for machining aspheric components were carried out. The grinding results indicated that the achieved profile accuracy is 0.3 mum and the surface roughness is less than 0.01 mum.