Dynamic Analysis of Robotic Manipulator for Incremental Sheet Metal Forming

Incremental sheet metal forming (ISF) process is an emerging technology used in various sectors of industries to reduce the cost of dies and for flexible manufacturing. Robotic assistance in ISF, like in other manufacturing processes, has been attempted by several researchers to make the processes more flexible and efficient. Hence, in addition to the conventional ISF process description, a detailed account of robotic assistance in ISF is also explained here. When a serial robot is used as a machining platform, most of the original tooling and machinery can be preserved. On the other hand, when such machining process is adopted to be used for ISF, due to varying forming forces and as stiffness of the robot may not be high, forming tool may deflect causing error in tool path, which in turn results in errors in geometry of the part. In order to compensate for this deflection, knowledge about the level of stiffness of robot in all its configurations and prediction of forces with sufficient accuracy are required. Hence, developing a procedure to predict forming forces is explained here. This will include dynamic analysis of a two-degree-of-freedom serial manipulator which is to be used in the forming operation. Dynamic analysis will give variation of forces with respect to the movement of links and joints used. Using the results of dynamic analysis, dimensional synthesis can be done which will also include determining link lengths. Inverse dynamic model is used to obtain the joint torques and forces for desired acceleration of platform using the state variables of the robot, i.e. the position and velocities. After finding out dimensions of link and joints, workspace volume is to be found out. To investigate the reliability of the proposed design for dynamic performance, multi-body dynamic (MBD) analysis and simulation of the manipulator is done using COMSOL Multiphysics. In the present work, task of the robot is to carry and manipulate sheet metal on which incremental forming operation is performed. Robotic manipulator manipulates the sheet with respect to 3-axis CNC tool to get a final shape. We mainly focus on dynamic analysis of a serial two-degree of freedom (2-DOF) robot used for incremental sheet metal forming.