Study of Forming Accuracy and Surface Finish in Multi-Stage Robot-Assisted Incremental Sheet Hydroforming of AA6061

Abstract This study presents the development of multi-stage robot-assisted incremental sheet hydroforming (MSRAISHF), an innovative process that integrates multi-stage incremental sheet forming (MSISF) with hydroforming to enhance formability, thickness uniformity, and surface finish in aluminum alloy AA6061 sheets. MSRAISHF was compared with single-stage RAISHF, revealing that multi-stage processing produced fixed wall angle conical frustums (FWACF) with improved forming depths and enhanced thickness uniformity along the wall of the cone. Notably, MSRAISHF reduced spring back by 60%, significantly improving the geometric accuracy of the formed parts. Surface quality also improved markedly, with reduced surface roughness and the suppression of undesired waviness commonly observed in single-stage RAISHF. To further assess the effect of multiple forming stages on surface characteristics, a Variable Wall Angle Stepped Conical Frustum (VWASCF) was designed. This sample was used to analyze the influence of forming stages on thickness distribution and surface finish. The results indicate that MSRAISHF is effective for producing sheet metal parts with improved surface finish and dimensional stability, making it suitable for applications requiring high accuracy and surface quality. Graphical Abstract