Multi-stage and robot assisted incremental sheet metal forming: a review of the state of art and comparison of available technologies
Incremental sheet metal forming is a recently innovated technology of achieving asymmetric sheet metal parts without using a die and through computer numerical control machine tool based path programming by inducing localized plastic deformation with a spherical ended tool. One of the major limitations of the existing method of incremental sheet metal forming is the limiting wall angle, where a wall angle of greater than about 70° is difficult to obtain. The recently proposed solution of multi-stage incremental forming can enable obtaining wall angles close to 90° but it takes longer manufacturing time and may pose problems for materials that severely strain harden. Robot-assisted incremental forming has a potential to offer an alternative solution for steel wall angle limitation but the existing work in the literature on robot-assisted incremental forming mostly focused only on the use of a standalone robotic manipulator instead of the limiting 3-axis CNC vertical machining center or a more expensive 5 or 6-axis vertical machining center. In this paper a review and comparative study of existing multi-stage incremental forming and robot-assisted incremental forming technologies in solving the limiting wall angle problem is presented.
Investigation of influence of part inclination and rotation on surface quality in robot assisted incremental sheet metal forming (RAISF)
Abstract In incremental sheet metal forming (ISF), by maintaining contact between tool and sheet metal can help in uniform thickness distribution and improved surface quality. In the present work the tool path versatility has been explored by transferring some of the tool-sheet relative movements to the work piece by using a two-degree of freedom robotic manipulator with an aim to improve surface finish and achieve greater wall angles. The robotic manipulator has been designed to orient the sheet metal part with respect to the forming tool fixed in the three-axis machine tool to form steeper wall angle parts with better surface finish. The effect of rotational speed, wall angle, tilting angle and tool linear step interval on forming quality in robot assisted incremental forming has been studied and analyzed. Steeper wall angles and better surface finish were found to be obtained with the help of the robotic manipulator than the conventional incremental forming. The results of design of experiments based parametric study on surface finish have been presented.
Model Identification and FE Simulations: Effect of Different Yield Loci and Hardening Laws in Sheet Forming
The bi‐axial experimental equipment developed by Flores enables to perform Baushinger shear tests and successive or simultaneous simple shear tests and plane‐strain tests. Such experiments and classical tensile tests investigate the material behavior in order to identify the yield locus and the hardening models. With tests performed on two steel grades, the methods applied to identify classical yield surfaces such as Hill or Hosford ones as well as isotropic Swift type hardening or kinematic Armstrong‐Frederick hardening models are explained. Comparison with the Taylor‐Bishop‐Hill yield locus is also provided. The effect of both yield locus and hardening model choice will be presented for two applications: Single Point Incremental Forming (SPIF) and a cup deep drawing.