Investigations into the hydraulic-pressure augmented deep drawing process

A novel hydraulic-pressure augmented deep drawing process for the manufacture of very deep cups from sheet metal is being investigated, refined and developed. Cylindrical cups have been drawn successfully from 1 mm thick aluminium blanks at draw ratio of up to 3.5 using this process. Research and development work on the present process completed to date is presented in this paper. The results presented include the variation of the hydraulic-pressure generated with the punch-stroke obtained from a finite element simulation, an analytical method, and from experimental investigations. The parameters studied include the draw ratio, the punch and die radii, the diameter of the stem of the punch, and lubrication. The limiting draw ratio, strains and thickness variations on the cup wall, and the hydraulic-pressure generated have been studied. Conditions leading to possible modes of cup failure, and ways of avoiding these are discussed. A method of reducing the blank-holding force applied on the flange of the cup, and steps taken to reduce the speed of the emerging cup to acceptable values, are described. Tooling for a draw ratio of 4.0 has been fabricated, and further investigations are being carried out presently. (C) 2000 Elsevier Science S.A. All rights reserved.