Investigation of the effect of die geometry and the radius on drawing ratio during deep drawing of square cross-section cups

It is difficult to achieve the squared shaped cups than cylindrical ones in the deep drawing method. The deformation resistance of the material at the corner regions is increased from the counter to the center direction and this result in some further damages such as wrinkling, breaking and tearing. On the other hand, the deep drawing process is directly affected by the following main factors: the shape and the geometry of the die, the mechanical properties of the material, the dimensions and geometry of the blank part, the friction and lubrication conditions between the die/material/blank holder, the blank holder force and the die cavity. Thus, it is important to choose the correct molding parameters in order to enhance the productivity.In this study, the effects of die/blank holder angles, die/punch radii and blank holder force on the limit drawing ratio, punch force and wall thickness were investigated both experimentally and numerically in angular deep drawing of square cups. For this purpose, the die/blank holders were machined 0°, 5°, 10° and 15°; while the die/punches were given 4 mm, 6 mm, 8 mm dimensions in radii, respectively. The DIN EN 10130?1999 sheet metal parts in 0.9 mm in thickness were used as the target material. The punching forces during deep drawing operations were recorded by a load cell conducted on the forming axis with 10-1 second intervals. A micrometer in 10-4 mm resolution was used to measure the variations in the wall thickness of the cups. The experimental results were also modeled using finite element method. ANSYS computer package program was used for this purpose. Full factorial experimental design method was used to collect the data. The ANSYS results were compared with experimental findings. Finally, it was observed that the new type?s of angular deep drawing dies with different angle values gave better results than conventional dies with higher drawing ratios. The limit-drawing ratio and the wall thickness values were increased from 1,77 and 0,590 to 2,32 and 0,742, respectively. The FEM model results were in a good agreement with the experimental results. The experimental results were statistically evaluated by analysis of variance (ANOVA) method.