Analysis and Automation of Polishing Motion of a Skilled Machinist by Handwork for Mold and Die

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The automated form machining has already been carried out by NC machine tool in manufacturing mold and die, however, the mold cavity surfaces are still polished by a skilled machinist's handwork. The purpose of this paper is to not only study polishing mechanism and properties of a skilled machinist by handwork, but also develop an automated polishing tool based on the analysis of polishing motion and the knowledge acquisition of experts.The results obtained are summarized as follows: (1) The surface roughness(R) is exponentially decreased with the increase of the number of polishing operation(N) and can be obtained quantitatively according to the following equation: R = (R_0-Re)exp(-aN) + Re where R_0 is surface roughness before polishing, Re is final surface roughness and a is exponential constant factor. (2) The curve of the stock removal vs the polishing times is expressed approximately with two lines and the intersection of the two lines corresponds to the critical polishing times in which the surface can be almost finished. (3) The developed automated polishing tool which is attached to the spindle of NC machine tool makes it possible to finish the surface like a skilled machinist by handwork. (4) Using new polishing parameter(N/(f/n)) consisting of the three factors of wheel revolution(n), feed rate(f) and polishing times(N), the surface roughness and the stock removal can be dealt with quantitatively regardless of polishing conditions.