Negative angle-forming die

A negative angle-forming die comprising:

• a lower die for mounting a thin plate workpiece onto a supporting portion thereof;
• an upper die descendable in a straight direction towards the lower die for forming the workpiece by abutting against the workpiece;
• a columnar body arranged in a freely rotating manner on the lower die, said columnar body having an intruding forming portion formed at an edge portion thereof;
• a slide cam having an intruding forming portion, said slide cam being arranged to oppose the columnar body in a freely sliding manner with respect to the lower die;
• an automatic returning tool arranged at the lower die for retracting the columnar body in a rotating manner to an extent with which the workpiece can be taken out from the lower die upon completion of forming, wherein the workpiece that is mounted on the supporting portion of the lower die is formed through the intruding forming portion of the columnar body and the intruding forming portion of the slide cam while the slide cam performs sliding movements, and after completion of forming, the columnar body is retracted in a rotating manner by the automatic returning tool such that the formed workpiece can be taken out from the lower die;
• a first cylindrical bearing support surface located in said lower die;
• a first cylindrical shaft located at a first end of said columnar body;
• and
• a first cylindrical bearing located between said first cylindrical bearing support and said first cylindrical shaft for supporting said columnar body in a freely rotating manner.

A negative angle-forming die comprising:

• a lower die for mounting a thin plate workpiece onto a supporting portion thereof;
• an upper die descendable in a straight direction towards the lower die for forming the workpiece by abutting against the workpiece;
• a columnar body arranged in a freely rotating manner on the lower die, said columnar body having an intruding forming portion formed at an edge portion thereof;
• a slide cam having an intruding forming portion, said slide cam being arranged to oppose the columnar body in a freely sliding manner with respect to the lower die;
• and
• an automatic returning tool arranged at the lower die for retracting the columnar body in a rotating manner to an extent with which the workpiece can be taken out from the lower die upon completion of forming, wherein the workpiece that is mounted on the supporting portion of the lower die is formed through the intruding forming portion of the columnar body and the intruding forming portion of the slide cam while the slide cam performs sliding movements, and after completion of forming, the columnar body is retracted in a rotating manner by the automatic returning tool such that the formed workpiece can be taken out from the lower die,
• wherein a connecting portion between the columnar body and the lower die is an arc having a length substantially equal to a quarter of a circle.