Method of producing press-forming punch and die

A method of producing a press-forming punch, comprising the steps of:

• preparing a master die and a master punch relatively movable toward and away from each other so as to define therebetween a die cavity, the master punch having a working surface partially defining the die cavity;
• while a first blank sheet is disposed between the master die and the master punch, relatively reciprocating the master die and the master punch together, thereby press-forming the first blank sheet into a press-formed panel complementary in contour to the shape of the die cavity;
• cutting down the working surface of the master punch by a predetermined depth of cut;
• fitting the press-formed panel in the master die;
• while a second blank sheet having a thickness equal to the predetermined depth of cut of the working surface is disposed between the master punch and the press-formed panel fitted in the master die, relatively reciprocating the master die and the master punch together, thereby press-forming the second blank sheet into a punch panel complementary in contour to the shape of the press-formed panel;
• and
• applying a back-up material to the rear surface of the punch panel to thereby produce a press-forming punch.

A method of producing a press-forming punch and a press-forming die in succession, comprising the steps of:

• preparing a master die and a master punch relatively movable toward and away from each other so as to define therebetween a die cavity, the master die and master punch having respective working surfaces jointly defining the die cavity;
• while a first blank sheet is disposed between the master die and the master punch, relatively reciprocating the master die and the master punch together, thereby press-forming the first blank sheet into a press-formed panel complementary in contour to the shape of the die cavity;
• cutting down the working surface of the master punch by at predetermined depth of cut;
• fitting the press-formed panel in the master die;
• while a second blank sheet having a thickness equal to the predetermined depth of cut of the working surface is disposed between the master punch and the press-formed panel fitted in the master die, relatively reciprocating the master die and the master punch together, thereby press-forming the second blank sheet into a first punch panel complementary in contour to the shape of the press-formed panel;
• repeating the second-named reciprocating step to thereby produce a second punch panel;
• applying a back-up material to the rear surface of the first punch panel to thereby produce a press-forming punch;
• cutting down the working surface of the master die by a second predetermined depth of cut;
• fitting the second punch panel over the master punch;
• fitting the press-formed panel over the second punch panel;
• while a third blank sheet having a thickness equal to the second predetermined depth of cut of the working surface of the master die is disposed between the master die and the second punch panel fitted over the master punch, relatively reciprocating the master die and the master punch together, thereby press-forming the third blank sheet into a die panel complementary in contour to the shape of the press-formed panel;
• and
• applying a back-up material to the rear surface of the die panel to thereby produce a press-forming die.