High-efficiency chemical-thermal co-assisted small ball-end magnetorheological polishing of hemispherical resonators through optimization of chemical additives

The hemispherical resonator gyroscope (HRG) is a high-performance gyroscope widely used in next-generation strapdown inertial navigation systems due to its exceptional accuracy, ultra-long lifespan, and high reliability. The core component, the hemispherical resonator (HSR), is a Ψ-shaped thin-walled structure fabricated from fused silica, whose polishing quality directly influences the overall performance of the HRG. Permanent-magnet small ball-end magnetorheological polishing (PSBMRP) has demonstrated the capability for full-surface, high-precision, and non-destructive polishing of the HSR. However, its relatively low material removal rate poses a challenge for mass production of HSRs. To address this limitation, a chemical-thermal co-assisted PSBMRP method is proposed in this study. Six common alkaline substances are selected as chemical additives for magnetorheological (MR) fluids. The effects of chemical additive types on polishing efficiency and surface quality are analyzed through polishing experiments with fused silica glass rods, and the optimal chemical additive is determined to be granular NaOH. Using MR fluid with NaOH under controlled conditions (temperature: 60 ℃; pH: 14), HSRs with diameters of 30 mm and 20 mm are successfully polished. The total polishing times are reduced to 19 h and 23 h, respectively, representing nearly a 50% reduction compared to conventional PSBMRP. Both types of HSRs achieve surface roughness below 7 nm, roundness errors of inner and outer spherical surfaces under 0.19 μm, and concentricity error relative to the axis below 0.21 μm. The corresponding quality factors (Q) reach 27.25 million and 17.40 million, with frequency splitting of 0.003 Hz and 0.004 Hz, respectively. To the best of the authors’ knowledge, these results represent the highest combination of polishing accuracy and resonator performance reported to date, offering a highly efficient and precise manufacturing strategy for next-generation HRGs.