The automatically controlled deep drawing of sheet metal is performed on a forming press, which consists of an upper and a lower tool. The forming press consists of an insertable die (drawing ring, on the bottom) and a punch surrounded by a blank holder (on the top). This blank holder is positioned just far enough from the edge of the die so that the punch does not cause wrinkles or creases. To ensure that the sheet blank slides smoothly over the edge of the die, the drawing ring and punch are rounded at their edges. The middle area of the drawing ring incorporates the negative of the later deep-drawn workpiece. The sheet metal forming process is as follows: The sheet blank is placed on the die so that it is fixed by the sheet metal holders. The blank holder moves downwards. The punch is then pressed onto the die basement using pressing force. The punch pulls the sheet blank along with it. After forming, the top tool moves upwards so that the deep-drawn part can be removed.
From a technical point of view, the forming is carried out by radial tensile stress and the resulting tangential compressive stress. The tensile stress prevents the sheet from thickening. When machining round metal sheets, the compressive stress reduces the diameter in the edge area. If the desired drawing depth cannot be achieved in a single pass, the forming is carried out in several iterations. If the sheet is deep-drawn using a pressure-regulated water cushion, higher drawing ratios occur.
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