Geometrical Accuracy in Two-Stage Incremental Sheet Forming with Active Medium

Abstract

Incremental sheet forming with active medium (IFAM) is a modification of the well-known single point incremental forming (SPIF) and allows convex forming operations by applying pressure of an active medium on the bottom surface of the blank. Both convex and concave forming can be combined to a multi-stage forming strategy when the part is turned between these two forming steps. Experiments on a truncated pyramid are conducted to evaluate the influence of the two-stage forming strategy on the geometrical accuracy in comparison with an equivalent single-stage forming strategy. The findings indicate that the height of the convex preform has a major impact on the final accuracy. If the height of preform amounts 75% of the target height, the undesired bending in the flange region is significantly reduced and can be explained by a decreased vertical forming force. This effect leads to an increased geometrical accuracy in contrast to single-stage SPIF.