Analysis of draw-wall wrinkling in the stamping of a motorcycle oil tank

In the present study, the wrinkling problem occurred in a stamping part used for a motorcycle oil tank was studied using the 3-D finite element analysis. The material flow due to the original die design was first examined and the possible reasons causing the wrinkling problem were then identified based on the finite element analysis. In order to eliminate the wrinkles, the effects of the process parameters such as blank-holder force, blank size and draw-bead locations on the formation of wrinkling were studied and possible solutions were tried. However, the wrinkle problem could not be improved by changing the process parameters only. A detailed investigation on the material flow during the wrinkle formation process revealed that the uneven stretch between the highest portion of the part and the draw-wall at the part edge caused the wrinkling problem. After releasing the corner angle and cutting off some portion of the sharp corner, a sound part without wrinkles was achieved and the optimum die shape was determined. The modified die design for eliminating wrinkles is validated by the defect-free production part. The good agreement between the simulation results and the measured data obtained from the defect-free production part confirms the accuracy of the finite element analysis.