| In recent years,with the rapid development of precision instruments,optical technology and 3C and other industries,materials such as aluminum alloy,sapphire and single crystal SiC have been widely used in handheld devices,intelligent wearable,integrated circuits and other fields.These materials are required to have the characteristics of ultra-flat,ultrasmooth,no surface damage and so on.The traditional machining technology has some problems,such as surface damage and low machining efficiency,so it is difficult to obtain the ideal machined surface.In order to solve the above problems,the promising surface contact ultra-precision magnetorheological polishing technology is applied to 3C manufacturing industry,which avoids the problem of low machining efficiency of point contact and line contact polishing.In order to improve the efficiency of magnetorheological processing,based on the comparative analysis of domestic and foreign scientific researchers,a ring machining technology based on the idea of surface contact is proposed.It provides an efficient machining method for the manufacture of ultra-smooth plane with surface accuracy in micron level.The main research work of this paper is as follows.(1)The cylindrical permanent magnet polishing head was experimentally studied,and its surface defects were explored.It is proposed that there is a "ring effect" in the processing of cylindrical permanent magnet polishing head.The influence law of magnetic field strength,machining gap and rotating speed on the effective processing distance of "ring effect" was studied by single factor experiment method,which laid a foundation for future technological research.(2)Based on the "ring effect",a cylindrical permanent magnet magnetorheological polishing head was designed,which was compared with the cylindrical permanent magnet polishing head.The surface shape of the designed polishing head was greatly improved and formed.The uniform processing area is large,which verifies the feasibility of the scheme.On the basis of this scheme,the parameters of the polishing head are optimized,and the appropriate permanent magnet diameter,magnetic pole interaction form and magnetic pole combination form are selected.(3)The abrasive grain processing model in the magnetorheological polishing pad was established from the microscopic point of view,and the force and motion analysis was carried out.The removal mechanism of the single abrasive grain was analyzed and extended to the material of the polishing pad on the surface of the workpiece.The removal mechanism was further studied and analyzed,and the important parameter polishing pressure in the removal mechanism of the cylindrical permanent magnet magnetorheological polishing head was analyzed.(4)Using the self-built magnetorheological polishing machine and the polishing fluid equipped with SG MRF2035 magnetorheological fluid,the process parameters of magnetorheological machining on 6061 aluminum alloy workpiece were studied systematically by means of single factor experiment.Including the effects of magnetic field intensity,rotating speed,machining gap,processing time and abrasive concentration on the surface roughness and material removal rate of 6061 aluminum alloy workpiece,the optimum process parameters of magnetorheological plane polishing of cylindrical permanent magnet for 6061 aluminum alloy workpiece were obtained.The smooth and flat magnetorheological polishing of the annular machining area is realized. |
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