Forming of regularly spaced deep recesses on aluminium sheet metal panels

Abstract Recesses of depth 10 mm, width 7.7 mm and length 332 mm are needed to be formed at regular intervals of 60 mm on 370 mm wide and 1 mm thick aluminium panels for applications in the aircraft industry. The forming process entails bending along the length of the recess and stretching and drawing at the two ends. A die for forming these recesses progressively in two stations has been designed, constructed and tested. In the first station of the die the recess is formed to a depth of about 9.5 mm, the flow of the material being facilitated by the provision of generous punch and die radii, and by keeping the shape of the recess symmetrical, When the forming in the first station is completed, the die is opened and the sheet metal moved manually to the second station, where the already-formed recess is hooked onto the punch to keep the interval between the recesses at exactly 60 mm. When the die is closed again the recess that is already formed is restruck by the heavy springs in the second station, while another recess is formed at the first station. During restriking, the recess is pressed to its final asymmetrical form with sharp radii, and to its final depth of 10 mm. The design and development of the tooling and the results obtained from tests conducted with it are presented.