Method and apparatus for producing thin walled tubular product with thick walled flange

A method for forming a thin walled tubular member with thickened flange portion, comprising:

• providing blank of a plate shape;
• subjecting the plate shaped blank to a first stage drawing process by using a drawing die of conical shape in such a manner that a cup shaped semi-finished product having an inclined free end portion located on a conical surface of the drawing die is obtained;
• subjecting said cup shaped semi-finished product to a second stage drawing process by means of a die and a punch for obtaining a forward and rearward combined extrusion forging for obtaining a reduced thickness of a tubular portion of the cup shaped semi-finished product and for causing a stepped portion to be created at a location below said reduced thickness portion of the cup shaped portion, in a manner that the metal is, at the final stroke of the punch, flown to a shoulder portion of the stepped part and the reduced diameter part of the stepped portion;
• and
• simultaneously with said second stage drawing, flattening said inclined free end portion of said semi-finished product, while limiting the outer diameter of the end portion of the semi-finished product to a predetermined value, thereby further thickening the flange portion of the tubular product, thereby obtaining a tubular product with a thickened flange portion.

A pressing apparatus comprising:

• a three axis driving mechanism having two operating cylinders on one side and an operating cylinder on the other side;
• a first die set comprising a drawing die of a conical shape, a drawing punch, a piercing punch and a work ejecting head which is able to function also as a piercing die;
• a second die set comprising a shaping punch, a confining die, an inner holding punch, a bottom counter punch and a die and a punch functioned as also for piercing;
• said shaping punch and said confining die in second die set having an outer limiting wall for preventing an outer diameter from being increased which a highly thickened flattened end of a material to be processed is needed;
• in said first die set, a connection to said cylinders being such that said drawing punch and said piercing punch cooperate with said two cylinders on said one side while said work ejecting head cooperates with said one operating cylinder on the other side;
• in said second die set, a connection to said cylinders being such that said shaping punch and said inner punch cooperate with said two cylinders on one side, while said bottom counter punch cooperating with said other operating cylinder on the other side.