Simulation And Experimental Research On Polishing Micro-structure By Using Abrasive Water Jet With Profiling Nozzle

Microstructure array is widely used in industrial field,which requires high surface quality.Ater the ultra precision machining,the surface usually has scratches,also certain defects existed in tips and edges,which needs further polishing processing.At present,it’s not easy to polish microstructure array that the width is over 0.5 mm,depth to diameter ratio is greater than 1 because of limited traditional polishing methods,difficulty in manufacturing polishing tool and uniformally distributed grain.Abrasive jet polishing is possible with its characteristics such as machining arbitrary surface shape,strong flexibility,easy control and low cost.Therefore,a kind of method called polishing micro-structure by using abrasive water jet with profiling nozzle(PNAWJM)was put forward to further improve processing efficiency and solve problems,the main research contents include the following:(1)Based on the material removal theory of axial impact and tangential shear wear of a single abrasive particle,the PN-AWJM material removal model is deduced by piecewise-fitting the expression of spatial concentration and velocity distribution function of abrasive particles on each wall of the groove with matlab.(2)The abrasive water jet flow field of a profiling nozzle and the material removal shape of the grooves wall surface are numerically simulated.the shapes of the material removal from the micro channel wall are predicted by vertical and oblique incidence.The effects of nozzle structural parameters,such as nozzle diameter,cutting width of flow limiting groove and external pressure on the velocity and pressure flow field were investigated.The results show that increasing the pressure appropriately and reducing the nozzle aperture can improve the wall shear velocity and enhance the material removal ability.(3)The experimental device for polishing microstructure of profile nozzle abrasive water jet was designed and built,including pressure supply and regulation unit,abrasive circulation supply unit,jet unit and auxiliary unit.The selection and design of important components,properties of experimental materials and testing instruments are described.The suitable range of processing parameters was determined through pre-experiment,and the feasibility of the experimental device was verified.(4)The process parameters were tested for different nozzle types,number of nozzles,inlet pressure,processing time,abrasive particle concentration and abrasive particle size.The results show that the profile single nozzle 1 with finite flow groove is better than that of profile single nozzle 2 directly inserted into the micro-structure workpiece.The profile double nozzle can be applied to two micro-groove structures at the same time,but the surface machining quality is lower than that of the same type single nozzle with the pressure decreasing.The surface roughness Ra of bottom wall and side wall is 69 nm and 80 nm,respectively,under the conditions of 0.8 MPa machining pressure,3% abrasive particle concentration,3 μm abrasive particle size and 30 min machining.