Numerical and experimental investigation on the effect of surface curvature and slope angle on the material removal characteristics in fluid jet polishing

Fluid jet polishing (FJP) has been extensively utilized in the ultra-precision manufacturing of freeform optical components and molds. The form accuracy is mainly improved by controlling the polishing dwell time at different positions, which is determined by the deconvolution of the initial form error and tool influence function (TIF). However, in previous studies, the erosion-induced TIF is considered constant without accounting for the freeform surfaces' curvature and slope angle variations. Due to the deviation of TIF, it is still a challenge to achieve a high form accuracy for freeform surface polishing. In this paper, the TIFs in freeform surface polishing have been modeled by computational fluid dynamics (CFD) analysis. A series of spot polishing experiments subsequently were conducted on the surfaces with different curvature radii and slope angles. The experimentally measured data including cross-section profiles of polishing spots, Peak-to-valley (PV) value, and material removal rate are found to agree well with the model simulation results, which verified the effectiveness of the CFD model. The effect of surface curvature and slope angle on the material erosion distribution was investigated and revealed by the fluid flow field distribution, abrasive impact, and abrasive trajectories. This paper not only provides a deep scientific understanding of the material erosion characteristics in FJP of freeform surfaces, but also offers a simple and cost-effective solution to build the database of TIFs on freeform surfaces under various conditions, which is beneficial for the ultra-precision form control during FJP of freeform surfaces.