| 摘要 |
PURPOSE: To form a cylindrical outer circumferential wall at a rim part symmetrically on an axis and to make its end edge the same height, in forming a cup-shaped article with ruggedness on its bottom by means of a backward extrusion method. CONSTITUTION: While the main body 2 of a punch 1 advances nearly of a half reduction strokeαof the entire reduction stroke S that is required for forming, the main body 2 of the punch and a die 10 holding a base material M are relatively made one revolution, and then the relative revolution is stopped, with reduction imparted to the last stroke position of the main body 2 of the punch, to complete the forming. As a result, mechanical working for making the end edge of a rim part the same height is dispensed with, and the number of processes of the next stroke is reduced, improving the yield of materials.
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