Development of a measuring endoscope for the in-line quality control of filigree form elements in forming production lines

The Leibniz Universität Hannover, the Technische Universität Dortmund and the Friedrich Alexander Universität Erlangen-Nürnberg are developing in the frames of the collaborative research centre SFB/TR73 a new kind of technique for sheet forming, the cold sheet-bulk metal forming (SBMF). With the help of the new technology workpieces with complex geometries and filigree side elements are manufactured, true to size and ready for assembly, in a multistep forming process. Expensive chipping processes become dispensable and the process chain is being significantly shortened. The new method combines cold sheet forming with bulk forming. Within the research collaboration, material loads are examined from the level of crystal formations up to the behaviour of the holistic material by simulations and experimental verification. From the gained data, fitting materials for the process are being identified and tested in the also newly developed forming tools with respect to the process capabilities. For the analyses, adapted measurement devices are being developed that can be used to examine the workpiece as well as the tool. Two main aspects are in focus, during the development of the new measurement devices. On the one hand, at the end of the project, the systems shall to be capable of taking in process tool and workpiece measurements in the cycle time of the production line. Abrasion or lack of dimensional accuracy is intended to be detected in real-time and be notified to the process control system. On the other hand, the system is going to be used during the development of SBMF to take measurements of the new tools to detect abrasion parameters in the early development phase and to find methods for reduction. In the frames of this work the development of a high resolution 3-dimensional (3D) measurement endoscope is described that meets the explained requirements of sheet-bulk metal forming. The new device is based on image fibre optical image bundles that transmit fringe patterns from a new kind of fringe projection system to a newly developed sensor head directly in the inner geometries of a forming tool. Key aspects of the work are the development of adopted light sources and optics for the fibre based fringe projection to gain a high depth of focus in the measurement area as well as algorithms for the camera calibration and evaluation of the measurement data on the example of selected test geometries.