Vertical wall surface forming of rectangular shell using multistage incremental forming with spherical and cylindrical rollers

A multistage incremental sheet metal bulging machine using spherical and cylindrical rollers has been developed for vertical wall surface forming of rectangular shallow shells. The multistage incremental forming comprises three operations: bulging with a spherical roller, right-angle forming and flattening with cylindrical rollers. The hand-operated bulging machine formed a vertical wall surface, which is highly precise and preferred by designers. A method of calculating for the approximate distribution of thickness strain and the maximum bulging height of the rectangular panel was proposed using the deformation limit diagram obtained from the incremental bulging test with a ball roller and a geometrical plane-strain deformation model with a constant strain gradient. The predictions for the rectangular shell were reasonably in good agreement with experimental values for the annealed aluminum sheet.