Design Method for Forming Tools for Rotary Draw Bending of Bend-in-Bend Geometries

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Rotary draw bending (RDB) is widely used for production of bent tubes or pipes with small radii. The resulting geometries are generated by the contact surfaces of tools. These contact surfaces of the forming tools are currently designed using finite element (FE) simulations as well as knowledge of specialists. The results of the real forming processes are usually different from calculated geometries because some physical effects are unaccounted for the simulation model. Especially their interactions and transient behavior during forming are neglected. This is more important for bend-in-bend geometries in which a sequence of two bends lined up without a straight intermediate part. For the second bend, the contour of the first defines the geometry of the cavity of the second tool. Even small imprecisions of the first bow lead to bigger geometrical deviations of the product. The goal of this research project is to reach a higher process stability by a different tool design. The method is to monitor sensor data of the process during a large quantity of product cycles and design a model of the forming process using this database. Additional sensors will be integrated into the forming tools and the bending machine to get a virtual image of the process. The goal of the first funding period (1st FÖP) is the digital representation (research focus A) and the data-driven, explainable model of the bending process (research focus C). Target values are the components geometries with regard to shape and position deviations of the bends as well as the component contour in the potential area of wrinkling. The Chair of Forming Technology (UTS) is responsible for the numerical modeling of the bending process, the determination of sensitive process variables that lead to fluctuating quality characteristics of the component, the selection and implementation of suitable sensors in the forming system and the development of automated, time-synchronized measuring peripherals. Furthermore, a method for parameterizing the tools geometries with respect of forming system parameters and real product geometries, is being developed. This forms the basis for the design of improved contact surface designs, using the data-driven process modeling in the 2nd FÖP. The Chair of Ubiquitous Computing (IUC) is developing the digitization of the process in the form of a data pipeline that, with regards to the 2nd FÖP, is able to combine the process data, expert knowledge and simulation models. This particularly requires an adaptation of data-driven and visual models for the RDB, specific feature engineering as well as classification and regression processes which will be based on random forest methods. The results of the work are a collection of comprehensible reference data sets with the data-based representation of the process sequence and first adaptations of explainable models in combination with domain knowledge and the analysis results learned.