FORGING ON 4-DIE FORGING MACHINES FEATURI NG WORKPIECE FORWARD FEED AND ROTATION

Edelstahl Witten-Krefeld GmbH has been operating four-die forging mach ines for over 30 years. A significant aspect of forging on such machin es is the forward feed and rotation of the workpiece. In die forging. a distinction is made between four techniques where the forward feed a nd rotation of the workpiece are concerned. Featured in the following is solely the case of four-die forging machines, where the workpiece i s moved in longitudinal direction after each stroke and rotated throug h an angle of < 45 degrees around the longitudinal axis.When forging w ith forward feed of the workpiece in longitudinal direction and simult aneous rotation, no symmetrical contact area comes about between the w orkpiece and the die. The shape and size of the contact area are decis ively influenced by the feed rate and angle of rotation per stroke if the deformation and entry diameter of the workpiece stay the same. Com pressive stresses predominate in radial direction due to the dies acti ng from four sides. The stresses in longitudinal direction are mainly compressive at the surface and tensile on the interior. Depending on t he forging sequence, only a small area of the dies is in contact with the workpiece at the ends. This in duces a different state of stress c ompared with forging of the centre zone, which can result in funnel-sh aped workpiece ends. The theoretical fundamental principles that have been developed are corroborated by analyses and tests and are used to optimize this forging variant as well as to reduce die wear. The resul ts partly also have an impact on the planning and construction of new four-die forging machines.