Formability of polycarbonate sheets in single-point incremental forming

The paper investigates the influence of tool diameter, sheet thickness, and geometry of the workpiece during single-point incremental forming (SPIF) of polycarbonate sheets. An experimental campaign was conducted and involved varying and fixed slope angle tests. The process was performed at room temperature. Cone and pyramid frusta geometries were analyzed. A FE model was developed to determine stress, strain, and thickness distributions during the process. Different defects affected the formability of the polymer, namely thinning, twisting, and wrinkling. Significant differences were found with respect to SPIF of metals due to mechanical behavior of the polycarbonate, in terms of amount of thinning, twisting, and wrinkling. The mechanism of development of the abovementioned defects was identified as well as how they are influenced by the process parameters. The comparison of fixed and varying slope angle tests indicated that these latter were not fully representative of the formability of the sheets. The presence of geometrical singularities in pyramid frusta affected the formability of the materials. This was due to great localization of thinning at the edges and the increase of the forming loads as approaching these regions.