Application of Taguchi method for optimization of finishing conditions in magnetic float polishing (MFP)

Magnetic float polishing (MFP) technique is used in the finishing of advanced ceramics, namely, silicon nitride (S3N4) balls for hybrid bearing applications. In this paper, Taguchi method [Genichi Taguchi, Taguchi Methods-Research and Development, ASI Press, Dearborn, MI (1992); K.E. Dehnad, Quality Control, Robust Design, and the Taguchi Method, Brooks/Cole, CA (1989)] is applied for optimization of the finishing conditions. Surface finish parameters, namely, Ra (arithmetic average) and Rt (peak-to-valley height) are considered as criteria for optimization. Important parameters identified that influence the surface quality generated during final mechanical polishing for a given workmaterial with a given abrasive (material and grain size) are (i) the polishing force; (ii) the abrasive concentration; and (iii) the polishing speed. Experimental results indicate that for the surface finish, both Ra and Rt, the polishing force parameter is the most significant. However, for the surface finish Ra, the polishing force parameter is the most significant, followed by polishing speed and then the abrasive concentration; while for the surface finish Rt, the polishing force parameter is the most significant followed by the abrasive concentration and then the polishing speed. The experimental results also indicate that within the range of parameters evaluated, a high level of polishing force, a low level of abrasive concentration, and a high level of polishing speed are desirable for improving both Ra and Rt. A comparison of the results obtained by the Taguchi method with single parameter (i.e., one parameter by one parameter) variation using a fine SiC abrasive (1 mu m) yielded similar conclusions regarding optimum conditions [M. Jiang, Finishing of Advanced Ceramics, PhD thesis (under preparation), Mechanical and Aerospace Engineering, Oklahoma State University (1997)]. However, Taguchi method can extract information more precisely and more effectively. (C) 1997 Elsevier Science S.A.