Investigation of drawability of rectangular cups in angular deep drawing dies

The deep drawing method is one of the indispensable sheet metal forming methods in the manufacturing industry. The formability of sheet metals with high-strength properties is important. Therefore, studies on the formability of sheet metal have accelerated today. In formability, parameters such as the form and geometric shape of the die, the mechanical properties of the sheet material, the primitive dimensions of the sheet, its geometric shape and dimensions, the friction and lubrication conditions between the die-material-blank holder, the blank holder force and the gap of the between die and punch directly affect the limit drawing ratio. For this, it is important to choose the appropriate process parameters correctly for the deep drawing process to be successful. In this study, the effects of die geometry on limit drawing ratio, punch force, cross-section wall thickness changes, and hardness distribution of the cups were studied to be determined in the production of rectangular cups by giving angles to the upper surface of the die and by giving angles to the bottom surface of the blank holder in deep drawing dies. For this, angles of 0°, 3°, 6°, and 9° were given to the die upper surface/blank holder lower surface. The experiments were carried out at a constant 1800 daN blank holder force and a constant 4 mm/s punch speed. In the experimental studies, the gap between the die/punch was 1.2 mm, and the bottom of punch and edge radii and the die throat radii were used fixed at 8 mm. St37 steel with a thickness of 0.9 mm was used in the experimental studies. During the experimental studies, the punch forces were recorded at intervals of 10-1 seconds by means of a force measuring dynamometer fixed perpendicular to the punch axis in the radial direction. Wall thickness changes of the cups were measured with the LH-600E model MİTUTOYO brand linear measuring contact precision tip linear measuring gauge with an accuracy of 0.001. Microhardness measurements were precisely measured with the PROCEQ brand hardness measuring device. As a result, the limit drawing ratio can be increased by giving angles to the upper surface of the die/bottom surface of the blank holder, and the maximum limit drawing ratio was obtained as β=2.31 at α=9º. The largest and smallest wall thickness in the cups were obtained as 0.910 mm and 0.371 mm. The maximum and minimum microhardness values were measured as 61.4 HRC, and 43.8 HRC and the average hardness value was 53.1 HRC. Keywords Angular Deep Drawing, Limit Drawing Ratio, Rectangular Cups