Method and device for deep drawing blanks made of sheet metal into flangeless moulded blanks

摘要

A method for deep drawing blanks, which are punched out of sheet metal that is painted or coated with film material, for example made of steel or aluminum, into flangeless molded blanks, wherein the blanks are formed to a crucible-shaped part, with a flangeless cylindrical edge, around a drawing core by means of a drawing bell of a drawing die, and a predetermined spring force is applied to the side of the edge opposite to the drawing bell during the forming of the edge of the blanks by means of a blank holder, characterized in that the spring force applied to the blank holder is spontaneously reduced substantially to zero shortly before the end of the drawing process.

主权项

1. A drawing die for deep drawing blanks which are punched out of sheet metal that is painted or coated with film material into flangeless moulded blanks comprising a drawing bell, a drawing core, a blank holder and a pneumatic spring which applies a spring force to the blank holder, wherein the pneumatic spring is formed by a gas volume in a chamber (30), which is sealingly closed by a piston (28), wherein the piston bears against the blank holder (22) by way of force transmission elements (24), and a venting valve (38) is associated to the chamber (30), wherein the venting valve (38) is actuated when the piston (28) arrives in a predetermined position, whereby the chamber (30) is suddenly vented.