Papers by Author: Masahiko Jin

Abstract: The effectiveness of ultrasonic vibration polishing, a polishing method in which an abrasive wheel is vibrated perpendicular to the polishing direction, was investigated. A 3mm diameter cBN abrasive electroplated wheel (#800) was used as the abrasive wheel, and it was vibrated at a frequency of 38kHz and a maximum amplitude of 5.0µm (0-p). Truncation was also performed to make the abrasive grain height of the wheel uniform. Two types of truncation were performed: film lapping and PCD lapping, and the effects of truncation were investigated. Polishing experiments were performed on SKH51, and a comparison was made with conventional polishing and the effects of truncation. The results showed that ultrasonic vibration polishing using a truncated wheel improved the polishing efficiency and surface roughness.

Abstract: The hole quality on sheet metal parts is directly dependent on the die design and process parameters. In conventional piercing process, the secondary operations such as shaving, reaming and grinding are needed for manufacturing the precise-dimensioned holed parts without any cracks, resulting in the increase of both production time and costs. The fine-piercing process, referenced to the fine-blanking principle, is used to produce the precise-dimensioned holed parts with smooth-cut surfaces over the whole material thickness in a single operation. However, it is difficult to achieve the suitable die design and process parameters for meeting the part requirements. In this study, the die design by chamfering punch cutting edge was investigated on both the experiments and the finite-element method (FEM). The results were compared with the results obtained when the conventional die design with the punch cutting-edge radius was used. The FEM-simulation results showed the amount of die-roll, smooth-cut surface, and cracks agreed well with the experimental results. The results showed that an application of punch cutting-edge chamfer results in a superior fine-pierced hole surface could be achieved. Furthermore, the mechanism and effects of the punch cutting-edge chamfer have been theoretically clarified on basis of the material-flow analysis and stress distribution.

Abstract: Considering the advantages of the fine-blanking process, the smooth-cut surface without further operation could be fabricated. However, one of the major problems of the fine-blanking is the occurrence of the die-roll formation. This problem is the main factor which affects the quality of the fine-blanked parts. In this study, to reduce the amount of die-roll formation, the application of back-up ring was proposed. The finite element method (FEM) was used to investigate the effects of back-up ring. In addition, the effects of bridge width were also investigated. The FEM simulation results illustrated that the mechanism of back-up ring and the effects of bridge width could be theoretically clarified base on the material flow analysis. The FEM simulation and experimental results showed the good agreement with each other. Therefore, the application of back-up ring could reduce the amount of die-roll formation on the fine-blanked parts. In this study, the amount of die-roll formation increased as the bridge width increase and it was constant at the bridge width of over 15 mm.

Abstract: The V-ring indenter geometry (angle, height and position) was investigated by using the finite element method (FEM) to theoretically clarify the mechanism and its action in the fine-blanking process. The FEM simulation results indicate that very small or very large V-ring indenter angles, heights, and positions cause difficulty in the rotation of the material-flow and that the hydrostatic pressure is generated with great difficulty in the blanked material; therefore, crack formation occurs easily. The application of a suitable V-ring indenter angle, height, and position significantly suppresses the formation of rotating flow, which results in increased hydrostatic pressure, and crack formation is consequently prevented.