Effectiveness of the flanging process depends on geometry of tools, material properties, etc. Punch is an important part of looting and its profile geometry and clearance with respect to die plays the very important role. In this paper, the influence of step punch profiles and gap between the die and the punch were studied using FEM simulation and experiments. FEM simulation of stretch forming process for aluminum alloy AA5052 was carried out using five different punch profiles at 1 mm and 2 mm clearance. Experiments are carried out to validate one case of the punch profile and gap. FEM simulation results were expressed in this way: strain distribution (direction of die profile radius), bending load distribution with displacement of punch, length of cracks, and crack propagation. The peak forming load, radial strain, and circumferential strain were obtained at least gap in every punch case. The edge crack length reduces with increment in clearance between punch and die. The bending load is obtained peak value for the two-step punch shape whereas this value is small for the four-step punch shape. Strain (radial and circumferential strain) attained higher values in two-step punch shape, while these values are the small for four-step punch shape. Therefore, a large number of step punch profiles (more stepped punch) is suitable for mitigation of cracks length in stretch flanging process (SFP).

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