Research On High Efficiency Magnetorheological Polishing Process With Block-shape Permanent Magnet Excitation

With the development of optical technology,ultra-smooth optics are urgently desired by many applications.Conventional ultra-precision polishing technology is inefficient and the machining quality is unstable.These are difficult to meet the demand of mass and low-cost production.Traditional magnetorheological finishing(MRF)technology use a wheel as fluid carrier and a small MR polishing tool was employed for deterministic machining by residence time controlling.This method can achieve high surface accuracy and low surface roughness.However,the process is inefficient and costly.In this paper,a high efficiency MRF method with block-shape permanent magnet excitation was proposed for ultra-smooth flat surface.In this way,the stiffened magnetorheological fluid with large area is formed so that the contact area between the workpiece and the stiffened magnetorheological fluid is expanded and the polishing process in the way of large area removal can be realized.This process improves both the surface roughness and the machining efficiency.The main research contents of this paper are as follows:(1)A new MRF method is proposed to improve polishing efficiency which by increasing the processing area and improving the magnetic field distribution.Then developed experiment apparatus that can meet the processing requirements.(2)According to the requirements of the experimental apparatus,select NdFeB permanent magnet series N50 which have a block-shape as the magnetic excitation device.Design and optimization the magnet dimensions using ANSYS software.Then the area where magnetic induction strength is greater than 300 mT reached 3000mm2,while magnetic induction is substantially uniform and magnetic field direction is almost consistent.(3)Preparation reasonable magnetorheological fluid for the polishing of K9 glass.Research the shape,acreage,and the relative position with the magnet of the polishing mark,by polishing mark experiment.Compared with conventional wheeled MRF,the acreage of polishing mark raised tens to hundreds of times.(4)Research the influence of machining parameters on the volume removal rate and the surface roughness after machining,such as polishing time,working gap,excitation gap,polishing disk speed,grit size,workpiece speed,and analysis the material removal mechanism.Compared with the traditional MRF method,volume removal rate increased significantly.