Springback effect evaluation in three-dimensional stamping processes at the varying of blankholder force

The quantitative evaluation of elastic springback in sheet metal stamping processes is still today a very interesting research topic, since this phenomenon causes a manufacturing shape defect. A measurement technique based on the shadow moire method, already developed by the present authors, has been further upgraded and applied to evaluate the springback phenomenon in the deep drawing of square boxes, the basic three-dimensional stamping process. In particular this technique is able to determine the final lateral surface of the drawn parts, once extracted from the dies, and to compare such surface with the ideal one derived from the die's computer-aided design (CAD) geometry. Proper quantitative coefficients are introduced to describe the investigated shape defect. The proposed technique is applied to a deep drawing operation of aluminium and steel square boxes and the influence of the blankholder force level on the elastic springback is taken into account.