Press molding method and press molding apparatus

Abstract

The present disclosure is applied to a press molding method for press-molding a workpiece by a press die composed of an upper die and a lower die while holding the workpiece by a die cushion. The press molding method according to the present disclosure includes pressing process, in which a press position at which the workpiece is pressed by the press die is gradually lowered while repeatedly pressing and releasing the workpiece by the press die a plurality of times until the press position reaches a bottom dead center, wherein in the pressing process, a holding force for holding the workpiece by the die cushion is controlled separately from a press molding force for press-molding the workpiece by the press die.

What is claimed is: 
     
         1 . A press molding method for press-molding a workpiece by a press die composed of an upper die and a lower die while holding the workpiece by a die cushion, the press molding method comprising pressing process, in which a press position at which the workpiece is pressed by the press die is gradually lowered while repeatedly pressing and releasing the workpiece by the press die a plurality of times until the press position reaches a bottom dead center, wherein in the pressing process, a holding force for holding the workpiece by the die cushion is controlled separately from a press molding force for press-molding the workpiece by the press die. 
     
     
         2 . The press molding method according to  claim 1 , wherein in the pressing process, holding and releasing of the workpiece by the die cushion are repeated a plurality of times. 
     
     
         3 . The press molding method according to  claim 2 , wherein when the workpiece is released from the die cushion, in a predetermined number of times of the releasing out of a plurality of times of the releasing, the workpiece is in contact with both of the press die and the die cushion, and in a remaining number of times of the releasing out of the plurality of times of the releasing, the workpiece is separated from at least one of the press die and the die cushion. 
     
     
         4 . The press molding method according to  claim 1 , wherein in the pressing process,
 at least one of an equipment state of a press molding apparatus, a material state of the workpiece, and a die state of the press die is monitored, and   the press molding force is controlled based on at least one of the equipment state of the press molding apparatus, the material state of the workpiece, and the die state of the press die.   
     
     
         5 . The press molding method according to  claim 1 , wherein in the pressing process, a die shape of the upper die and a die shape of the lower die are changed based on the press position. 
     
     
         6 . A press molding apparatus comprising a press die composed of an upper die and a lower die and a die cushion, configured to press-mold a workpiece by the press die while holding the workpiece by the die cushion, and configured to execute pressing process, in which a press position at which the workpiece is pressed by the press die is gradually lowered while repeatedly pressing and releasing the workpiece by the press die a plurality of times until the press position reaches a bottom dead center, the press molding apparatus comprising:
 a first control unit configured to control, in the pressing process, a press molding force for press-molding the workpiece by the press die; and   a second control unit configured to control, in the pressing process, a holding force for holding the workpiece by the die cushion separately from the press molding force controlled by the first control unit.