Development of a New Ultra-precision Finishing Process for Internal Surface by the Application of Magnetic Abrasive Machining Using Superconducting Coil

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The results obtained in this research during three years are summarized as follows :(1) High magnetic field strength of 3T (30000 Gs) in the working zone are first realized in our laboratory using freezing type superconducting electro-magnetic coil. (2) The internal finishing setup for non-ferromagnetic slender tubes (slender clean pipes of SUS304) was equipped on this supercoducting coil apparatus. (3) The mechanism of the internal ultra-precision finishing of a tube is discussed by the experimental results using mixed type magnetic fluid with ultra-micro abrasive grains and iron particles respectively. (4) From the experiments, it is clarified that the finishing pressur is infulenced by the both magnetic abrasive particle diameter (iron particle dia.) and the product value of the magnetic field strength and its gradient determined by N-S magnetic pole arrangemet. (5) The effect of magnetic field distribution on the finishing pressure by the modelling experimental setup using a conventional DC electromagnetic coil and rare earth permanent magnets. (6) The analytic results of the magnetic field distribution in the working zone by the Finite Element Method (FEM analysis) using a personal computer are equal to the measued value obtained using a tesla-meter sensor. (7) The difference between the magnetic field distribution of N-S pole arrangement and N-N (or S-S) pole arrangement is discussed by the FEM analysis. (8) The effects of N-N pole arrangement on the finishing characteristics are clarified experimentally, compared with N-S pole arrangement. (9) By this research using superconducting coil, very high magnetic field strength of 3T was actualy obtained in the research field of precision machining technology.