The head forming is mainly divided into 3 stages.

　　(1) The initial stage of deformation. The blank holder is pressed against the blank, and the punch is pressed down. First contact with the center of the blank, bending and stretching deformation occurs in the center area of the head for the first time, and the wall thickness is reduced. The wall thickness in other areas basically does not change. When the punch continues to be depressed, the contact area between the punch and the head becomes larger, and the center area of the head is completely connected to the punch. Under the action of large tensile stress near the central area, thinning occurs, and other parts of the blank are basically in a "straight line" state. In this process, the forming load increases slowly and smoothly.

　　(2) Metaphase of deformation. When the punch is pressed down, the straight section in the initial deformation stage will undergo a combined deformation of stretching and bulging under the action of external force. The billet near the center area becomes thinner under the action of deep drawing and bulging force, and becomes the thinnest area, and here is the area with large curvature change, which is easy to become the "no film" area. The curvature of the upper area changes little, making it easy to mold. Because the metal flows more intensely, the forming load of the punch increases faster, resulting in greater vibration.

　　(3) Anaphase of deformation. At this time, most areas of the head have been filmed, and the upper thickened area begins to flow into the gap of the upper die. Due to the limitation of the mold gap, the upper thickening area is thinned, the equivalent strain here is larger, and the straight edge is bent and deformed during the bonding process of the mold, and the forming load is the largest. Finally, the head gradually separates from the die, and the forming load decreases sharply until it reaches zero.