Defects and surface quality in single-point incremental forming of high-purity niobium sheets: a numerical–experimental investigation of toolpath effects

Abstract This study investigates the effect of toolpath strategy on the incremental forming of planar isotropic sheets of pure niobium. Fixed wall angle conical frusta were manufactured using two toolpath strategies: a conventional approach and a stair-based approach. Finite element analyses were employed to support the selection of process parameters and to predict the main process outputs. Experimental results show that the stair-based strategy reduces twisting and forming loads. However, despite the excellent formability of niobium, the surface quality remains inadequate. This limitation is attributed to the intrinsic material properties of niobium, indicating the need for dedicated surface treatment strategies to improve surface finish.