Numerical and Experimental Study of Producing Two-Step Flanges by Extrusion with a Movable Sleeve

The paper presents a new metal forming process for producing two-step external flanges on hollow parts. With this method, the flange is extruded by a movable sleeve, which moves in the opposite direction to the punch. This reduces the phenomenon of buckling of the tube wall, which allows extruding flanges with relatively large volumes. The new method was applied to produce a two-step flange on the end of a tubular billet made of 6060 aluminum alloy. This cold metal forming process was designed based on numerical simulations and experimental tests. The effect of the basic technological parameters on metal flow was investigated and limitations of the process were identified. The experimental results confirmed the possibility of forming a two-step flange with a diameter that is approximately twice as big as the external diameter of the tubular billet.