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Multi-pole arrangements in magnetorheological plane finishing technology have been investigated in this study. A method of combining the material removal mechanism of micro-points using the empirical Preston equation is proposed to establish a prediction model for surface flatness, and the new Semiconductor Equipment and Materials International (SEMI) standard has been used to evaluate workpiece surface flatness. Based on the model, the effects of process parameters (polishing time, speed ratio, translational amplitude, polishing gap, etc.) on the flatness of workpieces with different shapes are predicted through simulation, and the effects of multi-pole arrangements are explored. The results of the analysis indicate that with changes in process parameters, the extent of change in surface flatness differs based on the shape of the workpiece. After polishing, concave workpieces show the highest levels of surface flatness. From simulations of magnetic pole arrangements, it is also found that magnetic field generators with different magnetic pole arrangements can be used for workpieces with different shapes to improve their surface flatness. Experiments with a workpiece with its shape measured using a white light interferometer showed that the surface flatness improved from being 33.561 μm initially to 21.822 μm after polishing, thereby demonstrating the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Magnetorheological finishing, considered as a promising polishing technique that can finish a nano-level smooth surface and free of surface or subsurface damage, has been widely utilized in ultra-smooth polishing of hard-to-machine materials. However, there are still several practical weaknesses in magnetorheological finishing (MRF) applied for wafer surface polishing. In this study, a new method using MRF effect was proposed for wafer polishing. Concretely, porous foam was used as a storage carrier of MR slurry, and thus, MR slurry can be bounded in porous foam in the finishing process (cluster MR-porous foam polishing, CMRPP). In this paper, an experimental rig was constructed to achieve CMRPP mechanism, the processing principle and material removal process in CMRPP were analyzed, and CMRPP experiments were conducted to investigate the effects of porous foam on surface polishing. The results indicate the following: (1) The polishing forces in CMRPP were increased compared to that of a cluster MR polishing without porous foam (CMRP), and CMRPP can get a greater shear force than of CMRP at a same normal force; (2) CMRPP can well hinder the solid-liquid separation and sustain the stability of the slurry performance; (3) CMRPP achieved a higher volumetric removal rate than that of CMRP and improving of material removal efficiency; (4) CMRPP can effectively achieve a nano-level smooth surface compared to that of CMRP. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) ceramics play a key role in various engineering applications due to their desirable properties, however, they are typical hard-brittle materials and famous for their poor machinability. Ultrasonic-assisted grinding, a processing method hybridizing the conventional grinding and ultrasonic vibration (UV) machining, is employed as the one applicable machining method for hard-brittle materials. This study focuses on internal grinding of SiC ceramics with the assistance of the UV, and its ductile-brittle transition behavior in the grinding process were investigated experimentally. Following the processing principal of internal grinding and UV machining (i.e., UV-assisted internal grinding, UVAIG), the UVAIG experiment rig were constructed. Conventional internal grinding (CIG) tests, i.e., internal grinding without UV, were also performed on the constructed rig for comparison. In addition, the grinding force and the grinding chips variation behavior with the UV amplitude were also investigated to explore the ductile-brittle transition mechanism in UVAIG. The experiment results evidence that (1) ductile mode grinding is easily achieved in UVAIG, and the critical depth of the cut is deeper in UVAIG than that in CIG, i.e., 0.072 μm in CIG and 0.093 μm in UVAIG; (2) increasing of the critical depth of cut in UVAIG is likely owing to the lower grinding force in UVAIG than that in CIG; and (3) the ultrasonic vibration acted on the axis of the grinding wheel helps in the removal of material on the work-surface, but decreases the grinding energy in the ductile-brittle transition. [ABSTRACT FROM AUTHOR]