A miniature freeform bending machine with post-bending kinematics for process control

• Applicants: Dr.-Ing. Christoph Hartmann; Professor Dr. Tim C. Lüth; Professor Dr.-Ing. Wolfram Volk
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing ; Automation, Mechatronics, Control Systems, Intelligent Technical Systems, Robotics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 538527325

A free-form bending machine makes it possible to form tubes and profiles into 3D geometries by means of a moveable bending head (5 or 6 degrees of freedom). A challenge of this incremental process are disturbance variables that are not or only with difficulty detectable, caused e.g. by material inhomogeneities and weld seams in the semi-finished product, uneven wall thickness distribution and changing tribological conditions. This leads to local uncertainties and deviations in the bent segments of the workpiece and, due to the leverage effect, finally to large global deviations. These process uncertainties vary depending on the semi-finished product and the geometry to be produced, and it is currently not possible to react to them in a targeted manner during the bending process. The state of the art is to determine the process control of free-form bending a priori and to adjust the control of the bending head on this basis. Usually, the manufactured component is measured and the process control is adjusted in a trial-and-error process if necessary. A direct feedback of the current actual state for the process adaptation under consideration of the global dimensional accuracy does not exist so far. Within the scope of the research project, the fundamental scientific questions are to be investigated, i.e. a robust inline acquisition of the current component geometry, the implementation of a required post-bending kinematics as well as the associated modelling for a global process control.For this purpose, a new manufacturing system is to be developed and set up in which a robot kinematic system or mechanism intervenes specifically in the bending process. During the process, the end effector of the kinematics picks up the component. An optical measuring system and a force-torque sensor on the end effector of the kinematics determine the current deviation from the target state directly in the running process. The interaction of the degrees of freedom of the bending machine and the robot kinematics now enable a locally and globally controlled bending of the component. In this project, a small-scale research demonstrator is to be set up, consisting of a bending machine and post-bending kinematics. The demonstration system will be designed for the bending of small metal profiles (size of straws). The models and methods developed on this system should be scalable and transferable. The transfer of the process, the models and the methods to scaled systems and processes is to be an essential part of a follow-up project.

• DFG Programme: Research Grants