Evaluation of surface roughness and wall thickness in the incremental stamping process with variation in the degrees of freedom of the contact tool

Abstract

In this study, the performance of a rotating semi-spherical tool (with two degrees of freedom) is compared with another rigid semi-spherical tool, both with a diameter of 8.0 mm. The stamping is performed on AA1100 aluminium blanks with a thickness of 0.8 mm, using a helical strategy and single point incremental forming technique, with a feed rate of 1000 mm/min, a step depth of 0.1 mm, without rotation on the machine spindle and petroleum jelly as a lubricant. The behaviour of Ra and Rq roughness and wall thickness is evaluated during the tests. Scanning electron microscopy and dispersive energy spectroscopy are used to observe the wear mechanisms on the surface of the samples. On this basis, the tools for incremental stamping must promote continuous contact with the blank without generating excessive friction. Our results show that the rigid tool presents the best working conditions for the AA1100 aluminium sheets because it generates less roughness in the stamped parts, when compared with the rotating tool (~ 54% lower in the final average of the Ra roughness). The scanning electron microscopy image reveals the presence of adhesion both on the contact tip of the rotational tool and on the rigid tool, showing that the adhesive wear mechanism is predominant in the single point incremental forming process and influences the final roughness of the stamping cones.