Apparatus and method for deep drawing of large-sized thin-wall curved surface parts with servo reverse bulging

A method for deep drawing of large-sized thin-wall curved surface parts with servo reverse bulging by an apparatus comprising a forming die, a jacking unit, and a power unit, wherein the forming die comprises an upper die, a lower die and a blank holder, the upper die and the blank holder are connected to a press machine, the press machine drives the upper die and the blank holder to move, the lower die is fixed on workbench surface of the press machine, the blank holder is disposed above the lower die, and a blank to be drawn is placed between the lower die and the blank holder;

• the jacking unit is disposed inside the lower die and is adapted to move along a moving direction of the upper die to deform the blank to be drawn, the method comprising the steps of:
• step T1:
• fixing the lower die of the forming die on the workbench surface of the press machine, while placing the blank to be drawn on the lower die, and centering the blank to be drawn with the die cavity of the lower die;
• step T2:
• lowering the blank holder to press the blank to be drawn, and forming a closed cavity on a flange side of the blank to be drawn;
• step T3:
• applying a blank-holder force to the blank holder, and lowering the upper die to contact the blank to be drawn;
• step T4:
• lifting the jacking unit upwards to contact the blank to be drawn, and enabling the blank to be drawn to deform reversely to form a convex hull;
• step TS:
• continuously applying the blank-holder force to the blank holder, and lowering the upper die further with the jacking unit lowered together so that gradually the convex hull reduces in shape;
• step T6:
• lowering the upper die even further with the jacking unit lowered accordingly until the blank to be drawn experiences the formation;
• and
• step T7:
• unloading the power unit of the jacking unit, returning the lower die and the blank holder, and taking out a resultant part.

A method for deep drawing of large-sized thin-wall curved surface parts with servo reverse bulging by an apparatus comprising a forming die, a jacking unit, and a power unit, wherein the forming die comprises an upper die, a lower die and a blank holder, the upper die and the blank holder are connected to a press machine, the press machine drives the upper die and the blank holder to move, the lower die is fixed on a workbench surface of the press machine, the blank holder is disposed above the lower die, and a blank to be drawn is placed between the lower die and the blank holder;

• the jacking unit is disposed inside the lower die and is adapted to move along a moving direction of the upper die to deform the blank to be drawn, the apparatus further comprising a cooling unit, a first cooling cavity communicating with the cooling unit being provided in the lower die, and a second cooling cavity communicating with the cooling unit being provided in the blank holder, wherein the method comprises the steps of:
• step S1:
• fixing the lower die of the forming die on the workbench surface of the press machine, while placing the blank to be drawn on the lower die, and centering the blank to be drawn with the die cavity of the lower die;
• step S2:
• lowering the blank holder to press the blank to be drawn, and forming a closed cavity on a flange side of the blank to be drawn;
• step S3:
• filling the lower die and the blank holder with the cooling medium to cool the lower die and the blank holder, and spraying the cooling medium on upper and the lower surfaces of the flange side of the blank to be drawn through the first cooling channel of the lower die and the second cooling channel of the blank holder to obtain a critical temperature for drawing;
• step S4:
• continuously applying the blank-holder force to the blank holder, and lowering the upper die to contact the blank to be drawn;
• step S5:
• lifting the jacking unit upwards to contact the blank to be drawn, and enabling the blank to be drawn to deform reversely to form a convex hull;
• step S6:
• spraying the cooling medium on an upper surface of the convex hull through a third channel of the blank holder so that a temperature of the convex hull is always below a critical temperature;
• step S7:
• continuously applying the blank-holder force to the blank holder, and lowering the upper die further with the jacking unit lowered together so that gradually the convex hull reduces in shape;
• step S8:
• lowering the upper die even further with the jacking unit lowered accordingly until the blank to be drawn experiences the formation;
• and
• step S9:
• stopping a supply of the cooling medium, unloading the power unit of the jacking unit, returning the lower die and the blank holder, and taking out a resultant part.