Establishing a magneto-finishing process applying hemispherical permanent magnets combined with a radiated magnetic field array for complex surfaces

This study introduces an advanced magnetic polishing (MRF) process designed to overcome the limitations of conventional MRF methods, which are fundamentally unable to machine parts with complex, especially concave, surface profiles. A novel machining method for these complex surfaces is presented. The research proposes an MRF process using a permanent magnet polishing head with a 2 mm hemispherical profile, in combination with a specialized machine tool built for experimental purposes. This setup was used to analyze material removal properties as well as the influence of magnetic fields on the part’s machining process. The study extensively explores the forces exerted by magnetic fields on magnetic fluids, their behavior, and investigates the theories of apparent viscosity, shear stress, and hydrodynamic pressure in the polishing center region. In addition, the main factors affecting the polishing process were also examined, including the polishing gap distance, solution concentration, polishing tool speed, and the polishing head’s approach angle relative to the part’s surface. To create a polishing process with a high-performance magnetic field source, a radial magnetic field array was proposed. Using the finite element method, simulation and analysis of the magnetic field array and the magnetic polishing head helped us determine the appropriate C-axis angle, which was given as 60°, which has the largest flux coverage density, thereby improving the polishing process. Experiments were conducted on a copper’s concave surface workpiece to understand its characteristics, compare them with the proposed theory, and determine this method's feasibility. The efficiency of this machining method has been proven to perform polishing at the nanometer level, when the surface roughness of the polished part reaches 4 nm. This advancement is expected to open up the possibility of achieving nanometer-level ultra-precision polishing for complex surface geometries and a wider spectrum of materials in the future. • An advanced magnetorheological finishing process for complex concave surfaces • A radiated magnetic field array for ultra-precision machining of complex surfaces • Examines magnetic field effects on MR fluid, including viscosity, shear stress, and hydrodynamic pressure • Optimises polishing parameters using a radial magnetic field array and finite element simulations • Achieves nanometer-level surface finishing on concave copper surfaces