| 摘要 |
PROBLEM TO BE SOLVED: To obtain a molding having high quality without occurrence of a neutral zone at the time of molding by controlling the moving acceleration difference of a punch and die constituting a cavity for molding so as to change this difference continuously. SOLUTION: A first hydraulic cylinder unit 20 is driven and the descending of an upper ram 34 is started by a cylindrical section 38 after a powder material is packed into a cavity 16. A second hydraulic cylinder unit 22 is driven when the pressure Pup of the upper punch 14 rises higher than a prescribed pressure P. The moving accelerationsαup ,αdown of the punch 14 and the die 18 are detected by means of acceleration detecting sensors 58, 62 and the signals thereof are sent to a CPU 28 which controls the driving of the first and second hydraulic cylinder units 20, 22 in such a manner that the acceleration difference betweenαup andαdown change continuously. The descending of the die 18 is stopped and the upper punch 14 is risen when the pressure Pup of the upper punch 14 attains the prescribed max. pressure Pmax . The releasing work of the molding is then carried out.
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