TPT March 2014

Article

Tracto-Technik GmbH & Co KG

GmbH & Co KG Classification of bending profiles for manufacturing complexity By Christopher Kuhnhen, Christian Mathes, Armin Schmidt, Matthias Hermes, Christian Gerlach, Michael Rohrmann, Bernd Engel and A Erman Tekkaya, University of Siegen, TU Dortmund University and Tracto-Technik GmbH & Co KG

geometry of the bending component. Moreover, with the existing wide range of different bending processes, material- specific restrictions can be exploited to a greater or lesser extent. Knowledge of the processes and their efficiencies is a determining factor on whether or not a planned product will bring in profits or losses in subsequent production. Meanwhile, knowledge of the functioning of a bending process is based on the level of education and the experience of the machine operator and the respective machine manufacturer [4, p.16] . For designers of bending components, the present situation is highly confusing and unsatisfactory with respect to the pre-selection of a bending process. There are pluralities of different processes as well as the thereby producible bending geometries. Common criteria for the assessment of complex geometries do not exist. Aim of the project The BMWi-funded research project “RoPro” of the Chair of Forming Technology at University of Siegen, the Institute of Forming Technology and Lightweight Construction (IUL) at TU Dortmund University and the bending machine manufacturer Tracto-Technik GmbH & Co KG, based in Lennestadt, Sauerland, Germany, aims to reduce the difficulties in choosing component-specific bending processes. For this, extensive searches of current standards and guidelines have been carried out. Thereby analyses of company-internal guidelines were carried out. These and other results from the project will be anonymously enclosed to a standardisation application to the Fundamental Technical Standards Committee of the DIN (German Institute for Standardization). The aim is to obtain a German or an international standardisation which establishes standards in the field of profile and tube bending technology. As a result of the project, designers of bending components receive a tool which suggests an effective and economic bending process based on bending geometry and semi- finished product. A bending process is considered effective if it allows for the bending geometry to be manufactured below specified tolerances. The economic efficiency analysis is based on individual investment costs of the bending processes, which are included in the tool. The core idea of the research project is the development of a matrix (see figure 1) which helps to identify the most suitable bending process based on a pre-selection of bending geometry and semi-finished product (material and cross-section) to be used. Thus, the creation of interfaces between semi-finished

Present situation There is a broad range of industrial applications for tubes and tube design. In particular, automotive lightweight design requires light structures paired with high stiffnesses. Here, tubes and profiles with closed cross-sections are especially suitable. With respect to the material used they display a high stiffness, eg as required for body design. Furthermore, with the help of different bending processes, varying lots of bending components can be produced cost-efficiently. The current prime example is the start-up sector of electromobility. Altered auto bodies require flexible production concepts even for small quantities. That way, new products can efficiently be placed on the market right from the start. This is a necessary first step for the establishment of electromobility as a mass product on the consumer goods market [1] . Despite all the advantages of the use of bending components, manufacturers of bending machines and their users are facing steadily growing customer requirements regarding the geometry of bending components. While technological restrictions remain, bending radii decrease, 3D geometries are complex and tolerances regarding surface contours and connection faces are low [2, p.28; 3, p.17] . The number of parts which need to be discarded due to bending-specific quality characteristics increases with the complexity of the Since mid-2011, the University of Siegen, TU Dortmund University and Tracto-Technik GmbH & Co KG (Lennestadt) have been working on the development of a cross-sector standard which can be used by suppliers of semi-finished goods, users and bending experts alike and which is intended to considerably simplify the design of bending components. This article presents criteria for the assessment of the complexity of the geometry of tube and profile bending components. Tube and profile bending components are currently experiencing an increased demand on the market. Reasons for this are declining product life cycles and an adapting value-added structure. Both customer- specific design of mass products and small batch production are moving into the focus of manufacturing. The increasing demand for bending components calls for a fast and production-orientated design. Frequently, these requirements cannot be met by the design engineer due to a lack of production-related know-how, which is a result of the vast amount of different bending procedures.

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March 2014