| 摘要 |
PURPOSE:To reduce the forming cost by segmenting an inner die to plural split dies, setting a spring on the central split die, and providing the forming projected surface part of every split dies with a gap. CONSTITUTION:A lower inner die 3 and an upper inner die 4 are set on an anvil 1 and a ram 2, respectively; a forming projected surface 5 is formed on the periphery of the die 3, which consists of a central split die 3A, a peripheral split die 3B, and an intermediate split die 3C. The outer peripheral surface of the die 3A and the inner peripheral surface of the die 3C are provided with an annular recessed groove 8 and an annular projected rib 9, respectively; the outer peripheral surface of the die 3C and the inner peripheral surface of the die 3B are provided with a recessed groove 10 and a projected rib 11, respectively. By this mechanism, down movement of the ram 2 forms a blank pipe W in a short time through gaps 12 and 13 between every split dies 4B and 3B and a buffering force of a ring spring 6, preventing buckling and curing generation. Therefore, the forming cost is reduced.
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