| 摘要 |
PURPOSE:To improve the productivity in drawing and to reduce the cost by providing a taper or stepping-shaped thinning part on the outer periphery of the bottom part of a blank and performing the forming. CONSTITUTION:As for a cup-shaped blank 7 what has a taper or stepping thinning part on the outer periphery at the bottom side is prepared. The forming punch 5 having a tooth profile 5a is stood on the mobile plate 4 supported via an urethane spring 4a on a holder 1 and a press punch 6 is arranged to the upper part as well. The punch 5 is inserted into the blank 7 to be set inside the die 3 and the drawing is performed by moving the press punch 5 downward. In this case the increase of the inner pressure is restrained with the periphery of the thinning part becoming the relief place of the material at the forming time. Consequently the forming load is uniformized and the accuracy of the forming tooth profile is improved. The productivity in drawing is also improved and the production cost can be reduced.
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