Development and optimization of FJP tools and their practical verification

Abstract

This article presents the recent achievements with Jules Verne, a sub-aperture polishing technique closely related to Fluid Jet Polishing 1. Whereas FJP typically applies a nozzle stand-off distance of millimeters to centimeters, JV uses a stand-off distance down to 50 μm. The objective is to generate a non-directional fluid flow parallel to the surface, which is specifically suited to reduce the surface roughness 2, 3. Different characteristic Jules Verne nozzle geometries have been designed and numerically simulated using Computational Fluid Dynamics (CFD). To verify these simulations, the flow of fluid and particles of these nozzles has been visualized in a measurement setup developed specifically for this purpose. A simplified JV nozzle geometry is positioned in a measurement setup and the gap between tool and surface has been observed by an ICCD camera. In order to be able to visualize the motion of the abrasives, the particles have been coated with fluorescence. Furthermore, these nozzles have been manufactured and tested in a practical environment using a modified polishing machine. The results of these laboratory and practical tests are presented and discussed, demonstrating that the CFD simulations are in good agreement with the experiments. It was possible to qualitatively predict the material removal on the processed glass surface, due to the implementation of appropriate erosion models 4, 5 in the CFD software.