Precision Profiling of Sheet Metals by Agile-Flexible Roll Forming Process.

The increasing demand for flexible, agile, and small-batch manufacturing has created a strong need for sheet-metal forming technologies capable of producing high-quality profiles without dedicated tooling. Conventional roll forming provides high productivity and dimensional accuracy for constant cross-section components; however, its limited adaptability restricts its use for customized and variable-profile production. Agile-flexible roll forming offers a promising alternative, but its industrial application depends strongly on the development of reliable toolpath strategies capable of controlling deformation forces, minimizing defects, and improving geometrical precision. This thesis investigates the precision profiling of sheet metals by the agile-flexible roll forming process, with specific focus on the FlexRoll machine prototype. The research addresses two main objectives: the development of detailed toolpath generation strategies for non-variable L-profiles, and the expansion of the process boundaries toward innovative components, including variable-angle profiles and longitudinally welded tubes. Numerical simulations and experimental investigations were carried out on different sheet materials, including AISI 304 stainless steel, AA5754 aluminum alloy, and DD11 steel, in order to evaluate the influence of toolpath design on forming behavior, defect formation, and final part accuracy. The results demonstrate that toolpath design is the governing factor in agile-flexible roll forming. The comparison between internal and external toolpath strategies showed that increasing the moment arm between the forming and support rollers reduces forming forces and improves deformation localization. A detailed parametric toolpath methodology was then developed by considering the flower pattern, flange width, bending radius, roller geometry, contact-point position, and its evolution during forming. The study identified secondary curvature as a critical defect in FlexRoll forming and showed that it is strongly related to non-ideal contact conditions and force redistribution during incremental forming. For variable-angle profiles, the results confirmed the capability of the FlexRoll concept to manufacture non-uniform geometries, while also showing that inappropriate toolpath transitions can lead to unstable contact and wrinkling. In tube forming, support-assisted strategies significantly improved cross-sectional quality, reducing ovality on average from 18% in the support-less condition to 4.5% with dynamic support and 3.6% with static support, although at the cost of higher forming forces. Overall, this thesis contributes to transforming toolpath design in agile-flexible roll forming from an experience-based practice into a systematic engineering methodology. The developed strategies provide a basis for predicting defects, selecting suitable tool movements, and extending the FlexRoll machine toward a broader range of high-precision sheet-metal profiles.