Fluid Jet Polishing

Fluid Jet Polishing (FJP) is a new finishing process in advanced optical manufacturing. The fluid jet polishing system is guide a pre-mixed slurry to the surface with a high speed by the use of a nozzle, and the material is removed by the collision and shear action between abrasive grain and the workpiece. The surface shape of the workpiece is exactly modified by controlling the parameters of FJP, such as pressure, direction, working time etc.Compared with conventional polishing methods, Fluid Jet Polishing has its own advantage: no tool wear occurs and the precision of surface shape may be controlled easily; the tool is cooling and removing debris in process for the slurry flows circularly continuously; in addition, it can be fit for polishing various complex shaped surface for the tool is one columned liquid, the polishing characteristics is not influenced by the polishing position such as edge effect etc. Therefore, FJP will be widely applied.This thesis is based on the fundamental research of FJP. Firstly, based on fluid dynamics, with the help of the complex potential function, the dynamics of the polishing liquid is discussed when the polishing liquid interacts with the workpiece; the action force between the abrasive grain and the workpiece surface is analyzed at the moment of their collision and after collision. The stationary impact that obeys Gauss distribution between the abrasive grain and the workpiece surface and the transverse shear that obeys circular distribution centered by the polishing center are obtained. The theory foundation is established for the research of the removal mechanism of the material.Secondly, based on experiments, characteristics of the polishing area by FJP and removal mechanism of material is investigated. The phenomenon that the removal area presents the ring structure of W-shape is obtained. Then the reasonable explanation is given with the jet and impact theories. We conclude mat in the process of FJP collision and shear play a dominant role in the removal of material, while impact plays a subordinate role.Otherwise, the influence of the process parameters of FJP, including jet pressure,working distance, jet angle and working time etc, on the removal rate of the workpiece is investigated. Then the relation curves between every individual parameter and the removal amount are obtained, and the rules of material remove are summarized. Then we obtained the best combinational parameters of FJP.Finally, following the surface roughness of optical element, we investigate the influence of the characteristics of abrasive grain on surface roughness of optical element in the process of FJP. By controlling other process parameters, in a certain jet pressure range, comparatively perfect optical surface can by obtained using polishing liquid mixed by CeO2. Accordingly, the feasibility that FJP will be applied in fine optical manufacturing is testified.In conclusion, in this thesis, we investigated the removal mechanism of material in FJP, the influence of the process parameters on the removal rate of the workpiece , the influence of the jet pressure and the characteristics of abrasive grain on surface roughness in the process of FJP. Consequently the theoretical and experimental basis was made for the next research on numerical control aspheric surface fluid jet polishing.