Parametric evaluations of geometrical discrepancies in single point incremental bending

The process of ‘single point incremental bending’ (SPIB) is a generative manufacturing process to produce complex free form shapes on sheet metal/thin structures. It employs a solid hemispherical tool to deform the thin structure/sheet metal to the desired shapes and geometries. This process can be easily accomplished on an existing computer numeric control machines or robotic platforms. Geometrical errors in sheet metal bending presents major hindrance in achieving the desired quality products. In incremental or generative form of manufacturing, these errors/discrepancies are manifold and complex in nature. In the present study, a detailed parametric evaluation (both experimentally and numerically) at varied level, encompassing various geometrical discrepancies incurred in SPIB has been attempted. The influence of varied material, its anisotropy and four major process parameters–thickness of sheet, tool diameter, bending angle in each increment and sheet aspect ratio on major geometrical errors have been evaluated. Geometrical errors in SPIB occur in the form of elastic spring, error in final bending angle due bending curvature at the fixed end and error due to sheet inclination at the free end. The magnitude of elastic springback increases with increase in the respective tensile strengths of each material and sheet aspect ratio in terms of height to length. It reduces with the increase in maximum bending angle and sheet thickness. Other parameters have negligible influence on the elastic springback during incremental bending. The findings also revealed that error due to curvature at fixed end and inclination at the free end are closely related with the elastic springback of the sheet during incremental bending.