Evaluation of the Reverse Deep Drawing Process to Produce Square Cup of Brass Without Blank-Holder

Deep drawing is the process of drawing sheet metal blank into a desired shape. A blank holder is used to prevent wrinkling in the product, especially with thin sheets. The implementation of this process requires the use of double action press, and when the blank-holder is eliminated, single action press can be used, thus saving energy. In the current study, a new arrangement of punch and die was adopted to produce a square cup of brass from thin sheet in a single stroke of reverse deep drawing without blank-holder. Square cup produced by pushing blank with a hollow square punch through a square outer die which has inner square die. The geometric shape of the blank and its dimensions can affect the determination of the wrinkling as well as the drawing load and the distribution of strain and thickness, in addition reducing the metal removed as a waste in the trimming process of product. To study the effect of this parameter numerically and experimentally, three shapes were employed, square, square with fillet at its corners, and circular blank. The results show that the square blank gave a successful square cup of 30 mm rib, and 20 mm height has 4 mm radius without wrinkling. The maximum load and thickness distribution were almost similar for all blanks and an apparent change appeared in the thickness of the base. The maximum strain value decreases in the square blank. The speed of the punch can affect the determination of the drawing load, so three punch speeds (3, 6 and 9 mm/min) were experimentally employed to investigate their effect on load. The results revealed that the speed of 6 mm/min was the best. Errors between numerical and experimental results don't exceed 10%.