Research On The Cluster Magnetorheological Finishing For The Typical Material Of Cell Phone Shell

With the rapid development of information technology,smart phones have become a necessity for people’s daily life.The shell has gradually become a new bright spot and a competitive focus for manufacturers to attract consumers to purchase cell phones.The polishing process of cell phone shell directly determines the appearance quality and processing cost of the shell,and also determines the sensory experience of consumer,in order to meet the consumers in the pursuit of increasingly higher sensory quality,the improvement or new application of the polishing process is imminent.This paper proposes the application of cluster magnetorheological finishing technology to the processing of mobile phone shell to meet the requirement of the diversity of shell materials,so as to realize the high efficiency,high precision,flexibility and adaptability of cell phone shell.In order to achieve ultra-smooth polishing processing of different mobile phone shell materials,series of experiments were conducted out to obtain the best polishing process parameters of different materials,and the characteristics of the polishing forces were analyzed.It lays a foundation for the application of magnetorheological finishing technology in the processing of the cell phone shell.In this paper,single-factor experiments were conducted firstly on two representative types of mobile phone shell materials,namely anodized aluminum alloy and zirconia ceramics,using a cluster magnetorheological plane polishing device.The influences of the machining gap,speed of workpiece and polishing disk rotational speed,the deflection range,types of abrasive,abrasive particle size and other process parameters on material removal rate and surface roughness of workpiece were studyed,and the optimum parameters of different materials were obtained.When the machining gap,the workpiece speed,the disc speed,and the deflection range are 1.1mm,350 rpm,60rpm and10 mm,repectively,the anodized aluminum alloy can be polished with mirror effect of Ra5.2nm by use oxidation cerium abrasive of 3um.And a super smooth surface of zirconia ceramics with Ra 8.1nm can be obtained by 3um alumina abrasive while the workpiecerotation speed is 400 rpm and the machining gap is 0.9mm.This paper also described the material removal process within different processing time,and the results showed that cluster magnetorheological finishing can effectively remove the surface defect and the sudsurface damage layer under the form of elastic-plastic removal,but the final polishing quality will be affected by the defects inside of the material.Then,in our research,we set up a platform to measure polishing forces by the use of Kistler-9171 type rotary dynamometer.The influences of different process parameters such as machining gap,workpiece rotation speed,rotation speed of the polishing disc,workpiece deflection,abrasive type and abrasive particle diameter on the polishing positive pressure Fn and the shear force Ft were discussed by the real-time measurement of force signals in cluster magnetorheological finishing process.And the polishing force characteristics of cluster magnetorheological finishing were analyzed based on the constraint morphology of abrasive particles under different process conditions.It was found that the effects of different parameters on the polishing force characteristics are different.As the processing gap increases,both the positive polishing pressure Fn and the shear force Ft gradually decrease,but the polishing positive pressure Fn decreases more significantly;As the workpiece speed and the workpiece deflection increase,both the positive polishing force Fn and the shear force Ft gradually increase and then decrease;Both the hardness,density,and shape of the abrasive all affect the polishing forces.The ratio of the shear force Ft and the polishing positive pressure Fn of the cluster magnetorheological polishing is between 0.1-0.2,but the abrasive particle size and the rotational speed of the polishing plate have a great influence on the ratio of Ft/Fn.At the end of the paper,the effect of different workpiece materials on the polishing force was briefly analyzed.It was found that different workpiece materials have almost no influence on the positive pressure Fn of the cluster magnetorheological finishing,however,the surface morphology and hardness of the materials will have a greater impact on the shear force Ft.