Mechanism Research Of The Cluster Magnetorheological Finishing With Dynamic Magnetic Fields

With the rapid development of science and technology today,the demand for ultra-smooth planar components in the fields of microelectronics,biomedicine,and optics is increasing.Usually,the surface roughness of components is required to reach nanometer level,and the requirements for surface processing quality are also increasing.high.Magnetorheological polishing is an effective definitive novel optical surface processing technology with ultra-smooth and low damage.It has the advantages of good polishing effect,no secondary surface damage,no suitable for traditional surface polishing and other conventional polishing,but traditional the magnetorheological polishing method utilizes the polishing "ribbon" and contact surface "point" processing,resulting in low processing efficiency.Based on the theory of clusters and the magneto-rheological effect of rotating magnetic pole dynamic magnetic field,the planar magnetic polishing rhythmic effect of dynamic magnetic field clustering is established by rotating the magnetic poles of the cluster arrangement.The magnetorheological polishing pad with dynamic magnetic field is formed by the synchronized eccentric rotation of the magnetic poles arranged in a cluster.The plane polishing test device and the workpiece holding device use the magnetic pole arranged in a cluster to rotate eccentrically with respect to the polishing disc to form a dynamic magnetic field,so that the magnetic particles in the magnetorheological polishing liquid move along the direction of the magnetic force line,and promote the redistribution of the abrasive particles on the polishing pad.Real-time recovery of the performance and shape of the cluster magnetorheological polishing pad to achieve high-precision,high-efficiency and uniform magneto-rheological polishing of the workpiece surface.On the clustering magnetorheological surface polishing with dynamic magnetic field device,single-piece workpiece polishing was performed on a 2-inch single crystal silicon wafer.The optimum process parameters for single workpiece polishing were obtained through single-factor test and orthogonal test: the machining gap and the eccentricity of magnetic poles are 1.0 mm and 6 mm,the workpieces are oscillated to Ydirection oscillation for 40 mm at the oscillation rate of 400 mm/min,and the rotational speeds of polishing disk,magnetic poles and workpiece are 60,70 and 350 r/min,respectively.By polishing the single crystal silicon substrates whose original grinding sheet showed a surface roughness of Ra 213 nm for 4 h using the optimized technology,the surface roughness reduced to Ra 2.46 nm while the average MRR reached to 0.0783?m/min.A magnetorheological surface polishing machine with dynamic magnetic field was used to simultaneously perform multiple workpiece magnetorheological polishing on three single crystal silicon substrates.The effects of different polishing methods on single crystal silicon substrates were compared and analyzed.Studies showed that polishing was performed on multiple workpieces.In this way,the dual-ring polishing pad can provide a greater number of micro-grinding heads to machine the workpiece.The three-workpiece tool head enables the single crystal silicon surface to have a higher linear velocity relative to the polishing pad during processing,thereby enhancing the abrasive to monocrystalline silicon.The plastic removal effect of the surface is suitable for the processing of large-size workpieces.The optimum process parameters of multi-workpiece polishing are as follows: the machining gap and the eccentricity of magnetic poles are 0.9 mm and 6 mm,workpiece of Y-oscillation,oscillation distance40 mm,oscillation rate 600mm/min,rotational speeds of polishing disk 50r/min,rotational speeds of magnetic poles 90 r/min and rotational speeds of workpiece 350r/min,after continuous processing of original grinding surface roughness Ra 0.48 ?m of the single crystal silicon substrate for 5 hours using the optimized technology,the surface roughness was reduced to Ra2.4 nm,the material removal rate was 0.0812?m/min,and an ultra-smooth,uniform surface was obtained.Based on fluid mechanics and Preston equation,the effect of process parameters such as the rotational speeds of polishing disk,magnetic poles and workpiece,eccentricity of magnetic poles,machining gap on the polishing pressure of the workpiece surface was studied,combined with the Preston equation and the three-way dynamometer test results.The theory of continuous magnetorheological effect of dynamic magnetic field is analyzed in depth.The constant pressure polishing andmaterial removal rate models of magnetorheological clustering with dynamic magnetic fields are established.The influence of various process parameters on the material removal rate is theoretically analyzed and compared with the polishing experiment.The results have good consistency.