Reducing edge error based on further analyzing the stability of edge TIF and correcting the post-edge algorithm in MRF process

Abstract

A precise and efficient edge-controlled method is of importance to ensure the final performance of the optical system. The authors put forward a novel method to reduce the edge effect in the magnetorheological finishing (MRF) process through further analyzing the stability of the MRF edge tool influence function (TIF) and correcting the post-edge algorithm of dwell time. To demonstrate the feasibility and advantage of this edge-controlled theory, two mirror substrates are taken as the experimental samples. The Φ 200 mm, R-200 mm concave sphere mirror (fused silica) is removed about 3 μm uniformly and the experimental results indicate that the edge error region can be effectively suppressed below 1.5 mm. Another Φ 610 mm, R-2100, K-1 lightweighting parabolic mirror is verified about the actual practicability. The residual error reaches RMS 6.5 nm from original RMS 182 nm after two run iterations; meanwhile, the edge effect is well controlled to a large extent. The simulations of edge error coincide well with the corresponding experimental results, which strongly verify the feasibility of the edge-suppressing theory presented in this paper.