Characterization of the tool influence function in a dual-axis wheel polishing process to achieve high material removal rates

Various computer controlled optical surfacing (CCOS) processes have been proposed and developed in previous researches for producing ultra-precision optical surfaces, based on the fundamental CCOS principles, i.e., predictable material removal and dwell-time based process control. The main limitation for using the CCOS processes in real industrial applications, however, is the low material removal rates related with most of the CCOS processes, due to the 'gentle' tool-workpiece contact feature, resulting in very slow material removal and long process cycle time. This paper presents a novel dual-axis wheel polishing (DAWP) technology using a semi-rigid polishing wheel, designed to achieve high material removal rates and high convergence rates of surface roughness. Modeling for the tool influence function (TIF) was carried out based on the finite element analysis (FEA) and the results of the material property tests, for predicting and characterizing the material removal behavior of the DAWP. Fixed spot polishing experiments on BK7 glass and fused silica were carried out using the DAWP tool, to verify the validity of TIF models and to acquire the variation of TIF and material removal rate under different processing parameters. The experimental results show that the measured and theoretical TIFs match rather well, and the DAWP tool can realize much higher material removal rates on both materials. A BK7 ground flat surface was polished to validate the actual polishing performance of the DAWP tool. After one pass polishing, excellent surface quality was obtained. The preliminary study in this paper shows that, the DAWP tool has a good potential to be used for making large size optical components, significantly increasing the polishing efficiency and reducing the process cycle time.