Feasibility of Motion-Capture Techniques Applied to Tube Bending

Abstract

Tube bending is one of the most relevant manufacturing processes for the production of structural elements, but it suffers from the problem of springback that requires the tuning of the process parameters at every launch of new production batches. Off-line optimization approaches can be found in literature, but they often require complex characterization of the material properties or the application of approaches based on numerical simulation analyses. So, the development of new and more flexible on-line approaches to measure and correct the springback is crucial especially for highly automated machines as for example the tube benders. The paper presents a new measurement approach, based on the application of motion-capture techniques, to provide real-time measurements of the bent tube orientation, in order to decrease the time for the set-up of the main process parameters. A new methodology as well as a new experimental apparatus for the in-line monitoring of the tube springback is presented, as well as the evaluation of its accuracy when applied to the industrial process. An Inertial Measurement Unit (IMU) is linked to the tube during bending and the measurements from three gyroscopes and three accelerometers are used to perform the computation of the tube orientation in the 3D space. The proposed approach appeared promising for the evaluation of the springback through the measurement of the final angular configuration reached after bending.