Digital process support in toolmaking by using optical metrology

Increasing demands on the quality of outer skin car body panels, shortening product development processes of new car models in the future fundamentally challenge manufacturing companies in international competition. Such challenges emerge, for example, in the field of toolmaking, which plays a decisive role in the valueadded chain due to its high time and costs share. Here, the high proportion of manual, experiencebased operations in tool tryout often leads to unstable processes requiring many iteration steps until approval. Blue, non-dry colour is applied on sheet metal which creates a spotting image that makes the contact areas between the forming die surface visible. In die tryout, spotting images provide a visual indication of the current phase and also serve as quality criteria of sheet metal components. For this reason, research work reported about in this paper deals with the development of a procedure for generating digital spotting images by using optical 3D coordinate-measuring technology to keep the spotting image permanently available during die tryout phase, for example on smart devices. In fundamental investigations, different influences on the spotting image due to light conditions and STL-mesh size of the scanned geometry are initially examined in order to quantify both the physical and the digital spotting image. The knowledge gained is subsequently validated and further improved by means of test with series press tools. The results demonstrate how digital and physical spotting images are generated and quantified for a reduced time in sheet metal simulation and die tryout phase of large press tools. This is achieved by the systematic provision of process parameters from the series production, such as the force transmission between the forming die surfaces, the local sheet thicknesses and the documentation of process variation in the blank holder by using digital spotting images.