Optimization of the Tool Influence Function for Small Tool Polishing Based on the Control of Polishing Pressure Distribution

In ultra-precision optical components polishing, the shape of the Tool Influence Function (TIF) is an important factor that affects the processing efficiency and processing accuracy of optical components. For a self-rotating small tool polishing device commonly used in computer-controlled optical surfacing (CCOS), its TIF deviates from the Gaussian shape, and the processing is prone to cause surface figure divergence. Inspired by the theory of eccentric compression, this paper proposes a method to optimize the shape of the TIF based on pressure distribution control. Based on the finite element method, a contact pressure distribution model is established. The influence of different positions of the pressure contact points on the contact pressure distribution is analyzed, and the position of the pressure application point that makes the TIF close to the Gaussian shape is determined. On this basis, a new type of small tool polishing device that can realize the above optimization method is designed. The optimized actual TIF is obtained, and an aspheric mirror processing experiment is completed. After three rounds of processing, the value of PV of the surface form error converged from 1861.180 nm to 64.875 nm, with a convergence rate of 96.5%. The value of RMS converged from 299.857 nm to 6.043 nm, with a convergence rate of 97.9%. The surface figure accuracy has reached the expected goal with the root mean square value less than 10 nm, which verifies the feasibility and effectiveness of this optimization method.