Manufacturing of combined convex-concave form elements by using active-medium support in incremental sheet forming
Final Report Abstract
In Incremental sheet Forming with Active Medium (IFAM), the pressure of a liquid or gaseous medium is applied to the underside of a sheet metal. The interaction of the tool path and the pressure of the active medium enables this process to create both convex and concave geometries and to combine them into convex-concave shapes. A unique feature of IFAM is that the pressure of the active medium required for plastic forming is significantly lower than in conventional hydroforming processes. Therefore, during the first funding period, the underlying forming mechanisms were investigated using experimental and numerical methods. The IFAM process also differs from other incremental processes in that the three-dimensional target geometry is reduced to a two-dimensional toolpath. Additional measures are required to improve the geometric accuracy, such as the use of conical tools or a final concave forming step. Moreover, machine learning methods offer great potential for the development of a closed-loop control for adjusting the product geometry. By using a Neural Network (NN) to predict the pressure for the next contour of the toolpath, a significant improvement in geometric accuracy can be achieved for convex truncated cones. The control strategy without consideration of the forming forces reaches its limits when it comes to producing more complex geometries with irregular contours. The aim of the second funding period was therefore to investigate the influence of forming forces on part geometry and to develop industrial-suited approaches for process control and monitoring using machine learning methods. After integrating a force measurement platform into the experimental setup, the analysis of the experimental data showed a linear correlation between the tangential forming force and the increase in height of the part geometry. It has been successfully demonstrated that it is possible to produce an irregular part by adjusting the tangential forming force. Furthermore, the superposition of the pressure load creates a risk of instability in the forming process, which can lead to cracks in the component. To address this, a monitoring approach has been developed that uses a recurrent NN to process the sequential data of the forming process and to predict the probability of component failure. In addition, it has been demonstrated that Computer-Aided Manufacturing (CAM) can be used to automatically generate the toolpath in IFAM, thus enabling the generation of free-form surfaces. To summarise, the applicability of IFAM for industrial manufacturing of components has been significantly improved.
Publications
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Incremental sheet forming with active medium. CIRP Annals, 68(1), 313-316.
Ben Khalifa, Noomane & Thiery, Sebastian
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Closed-loop control of product geometry by using an artificial neural network in incremental sheet forming with active medium. International Journal of Material Forming, 14(6), 1319-1335.
Thiery, S.; Zein El Abdine, M.; Heger, J. & Ben Khalifa, N.
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Flexible Manufacturing of Concave–Convex Parts by Incremental Sheet Forming with Active Medium. The Minerals, Metals & Materials Series, 549-561. Springer International Publishing.
Thiery, Sebastian & Ben Khalifa, Noomane
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Geometrical Accuracy in Two-Stage Incremental Sheet Forming with Active Medium. Lecture Notes in Production Engineering, 65-74. Springer International Publishing.
Thiery, S. & Ben Khalifa, N.
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Grundlagenanalyse der wirkmediengestützten inkrementellen Blechumformung zur konvexen Formgebung. Dr.-Ing. Dissertation, Leuphana Universität Lüneburg, Göttingen: sierke VERLAG
Thiery, S.
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Experimental Data for: Manufacturing of irregular shapes through force control in incremental sheet forming with active medium, GRO.data, V1
Thiery, S., Zein El Abdine, M., Heger, J. & Ben Khalifa, N.
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Manufacturing of irregular shapes through force control in incremental sheet forming with active medium. Advances in Industrial and Manufacturing Engineering, 10, 100157.
Thiery, Sebastian; Zein El Abdine, Mazhar; Heger, Jens & Ben Khalifa, Noomane
