Investigation of influence of part inclination and rotation on surface quality in robot assisted incremental sheet metal forming (RAISF) Swagatika Mohanty*, Srinivasa Prakash Regalla, Y.V. Daseswara Rao Department of Mechanical Engineering, Birla Institute of Technology and Science Pilani-Hyderabad, Hyderabad, India A R T I C L E I N F O Article history: Available online xxx Keywords: Robot Incremental forming Surface roughness Tilting angle Rotational speed Stepping interval A B S T R A C T 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. © 2018 CIRP. Introduction The manufacturing of sheet metal parts for automobile, aerospace and computer industries is currently mostly carried out using processes like stamping (Fig. 1(a)) and deep drawing, which require expensive part-geometry specific dies. These are profitable in mass production but unyielding in terms of geometric flexibility of the part. This lead to exploration into alternative sheet metal forming processes to increase process flexibility. ISF is one such process, in which no specific die is required for any geometry of the sheet metal part and is mainly based on combined stretching and bending of the sheet with the help of a narrow contact spherical ended tool. The most popular ISF so far has been the single-point incremental forming (SPIF) as shown in Fig. 1b. In SPIF, sheet is constrained by a backing plate in X, Y axis and a rotating tool incrementally moves down in the Z direction to form the sheet gradually. In single stage incremental forming, achiev- able maximum forming angle is found to be 60  –78  depending on the material, thickness of the sheet and process parameters [1,2]. But multi stage incremental forming (MSIF) is quite successful in forming steeper wall angle than single stage forming. But MSIF takes ample amount of time to form a single part. To improve the formability in single stage forming, TPIF has been introduced. TPIF uses either a partial die or a numerically controlled supporting tool. In TPIF if supporting tool is held by or replaced by a robot, the process is called roboforming. Use of robot to hold the sheet metal improves flexibility in forming operation. By proper tool path planning, complex parts and steeper wall angle parts can be formed in roboforming. Partial die also helps in improving the sheet formability but the process becomes part dependent due to use of expensive dies. Non axisymmetric mandrel and force feedback control was used for incremental forming [3]. Various robot assisted incremental sheet metal forming has been shown in previous papers [4]. To improve dimensional accuracy, two six degrees of freedom have been used for metal forming [5]. These robots use universal tool which is independent of part geometries. To increase the maximum wall angle limit, tilting of part is one of the options viewed in literature [6] and tool orientation affects the cutter work piece engagement region [7]. Changing of the part orientation and rotation requires adaptive tool path planning to maintain surface quality and formability. Five-axis machine may seem already to possess built-in all the necessary degrees of freedom facilities to achieve the process investigated in the present work, but in a five axis machine, all the five DOF have to be operated simultaneously. In addition, higher cost, complex programming, greater possibility of gouging and collision are the main drawbacks of 5 axis CNC machine. Table 1 shows the relative advantages of a retrofitted robotic manipulator * Corresponding author. E-mail address: swagatika.bits@gmail.com (S. Mohanty). https://doi.org/10.1016/j.cirpj.2018.04.005 1755-5817/© 2018 CIRP. CIRP Journal of Manufacturing Science and Technology xxx (2018) xxx–xxx G Model CIRPJ 465 No. of Pages 12 Please cite this article in press as: S. Mohanty, et al., Investigation of influence of part inclination and rotation on surface quality in robot assisted incremental sheet metal forming (RAISF), NULL (2018), https://doi.org/10.1016/j.cirpj.2018.04.005 Contents lists available at ScienceDirect CIRP Journal of Manufacturing Science and Technology journa l home page : www.e lsevier.com/loca te/cirpj