Investigation of the optimal parameters for the surface finish of K9 optical glass using a soft abrasive rotary flow polishing process

Abstract

A workpiece polished by soft abrasive flow polishing has the advantages of low damage and ultrasmoothness. However, due to the need to use a constrained flow path, the fluid dynamic pressure on the near wall surface of the workpiece has a gradient distribution, so achieving uniform polishing of workpieces of large size is difficult. To address this problem, this paper proposes a new method of soft abrasive rotary flow (SARF) polishing to achieve low damage, ultrasmooth, uniform polishing of a large-size K9 optical glass surface. A new SARF polishing system and a 6-outlet rotary polishing tool are designed. The SARF polishing principle is analyzed, and a polishing experiment is conducted on K9 glass. The experiment of surface roughness improvement of the K9 optical glass is designed by Taguchi method. Orthogonal arrays and the signal-to-noise ratio (S/N) are used to determine the optimal parameters for SARF polishing. Analysis of variance (ANOVA) is used to determine the effect of the main polishing parameters on the surface roughness of K9 glass. According to the results of the polishing experiment using a Taguchi L18 orthogonal array and S/N ratio analysis, the optimal parameters for K9 glass SARF polishing are revealed to be as follows: the abrasive material is CeO2, the polishing pressure is 0.35 MPa, the abrasive particle concentration is 5 wt.%, the average size of the abrasive particles is 0.7 μm, the polishing time is 1.5 h and the platform rotation speed is 10 rpm. After polishing the sample for 1.5 h under these parameters, the surface roughness decreases from the original value of Ra = 37.28 nm to Ra = 4.51 nm, and the surface roughness improves by 87.9 %.