Experimental And Theoretical Study On Abrasive Jet Polishing Process

The requirement of surface shape accuracy of optical elements and microstructure surface is getting higher.The traditional processing method can no longer meet the machining requirements of modern production,and it is urgent to have the processing technology with development potential.Fluid jet polishing is a non-contact ultraprecision machining technology that integrates hydromechanics,nanoscale material removal and surface technology.It also has the advantages of wide processing range and stable material removal.In this paper,the fluid jet polishing equipment is developed.The key problems of different process parameters and material removal mechanism are studied by the combination of experiment and simulation.,and the surface polishing profile is predicted by using the established surface formation model.The nozzle structure is optimized and the results showed that: The nozzle with a shrink angle of 40° and a length of 1.0 mm facilitates uniform distribution of the abrasive particles and removal of the workpiece material.The effects of different process parameters on polishing were analyzed by single point experiment.The results show that: Processing time has a linear trend to affect material removal depth.Pressure has an exponential trend to affect material removal depth.Distance affects the material removal width;The impingement angle is reduced,the maximum material removal depth is increased,and the surface removal profile is changed from circular to crescent.As the nozzle diameter increases,the material removal depth decreases rapidly,and the material removal volume first increases and then decreases.Based on computational fluid dynamics,a single-point erosion model of fluid jet polishing is established.The mechanism of material removal is studied by combining single-point experimental results.And the results show that the high-speed abrasive particles emitted by the nozzle collide with the surface of the workpiece to generate shear force for material removal.Pressure affects the abrasive particle velocity,which in turn affects the shear force.The change of the distance affects the abrasive trajectory,which in turn affects the particle collision position.The impingement angle affects the surface velocity distribution of the workpiece,which in turn affects the shear force distribution.The change of the concentration of the abrasive particles affects the number of particles on the surface of the collision workpiece per unit time;The change of particle size affects the amount of single abrasive material.Based on the single point erosion model,the jet surface generation model is established by convolution operation.The simulation results of linear polishing show that the model has stable removal effect.For the grating path and the cross path,the surface topography generated by the two paths is predicted by simulation,and the accuracy of the simulation results and the rationality of the surface generation model are verified by experiments.The surface topography of different feed speed and path spacing is predicted by using grating path.The results show that the feed speed only affects the material removal,and the path spacing affects both the surface morphology and the material removal.The K9 plane glass is polished by grating path,and the surface roughness is reduced from 360 nm to 187 nm.