Closed-loop control of product geometry by using an artificial neural network in incremental sheet forming with active m
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ORIGINAL RESEARCH
Closed-loop control of product geometry by using an artificial neural network in incremental sheet forming with active medium S. Thiery 1
&
M. Zein El Abdine 1 & J. Heger 1 & N. Ben Khalifa 1,2
Received: 17 September 2020 / Accepted: 3 November 2020 # The Author(s) 2020
Abstract A strategy to adjust the product geometry autonomously through an online control of the manufacturing process in incremental sheet forming with active medium is presented. An axial force sensor and a laser distance sensor are integrated into the process setup to measure the forming force and the product height, respectively. Experiments are conducted to estimate the bulging behavior for different pre-determined tool paths. An artificial neural network is consequently trained based on the experimental data to continuously predict the pressure levels required to control the final product height. The predicted pressure is part of a closed-loop control to improve the geometrical accuracy of formed parts. Finally, experiments were conducted to verify the results, where truncated cones with different dimensions were formed with and without the closed-loop control. The results indicate that this strategy enhances the geometrical accuracy of the parts and can potentially be expanded to be implemented for different types of material and geometries. Keywords Incrementalsheet forming withactivemedium . Closed-loop control . Artificialneuralnetworks . Geometricalaccuracy
Introduction Incremental sheet forming with active medium (IFAM) is a novel manufacturing process to produce concave-convex geometrical parts in small lot sizes [1]. This process an extension of the well-known single point incremental forming (SPIF) by an active medium, which applies pressure on the bottom surface of the blank during the forming process. Depending on tool path and pressure control, concave and convex forming operations are feasible in IFAM and can be sequentially combined. Shaping complex parts requires neither intermediate turning of the blank nor a dedicated die nor a counter tool like other common incremental forming processes. Therefore, IFAM preserves the flexibility of incremental forming processes. The active medium can be gas or liquid. Ben Khalifa and Thiery [1] used pressurized air for convex forming.
* S. Thiery [email protected] 1
Institute of Product and Process Innovation, Leuphana University of Lüneburg, Universitätsallee 1, 21335 Lüneburg, Germany
2
Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Straße 1, 21502 Geesthacht, Germany
Moreover, Kumar and Kumar [2] utilized pressurized fluid for concave forming. Plastic deformation occurs only in the contact zone between tool and blank due to stress concentration. For this reason, forming forces and pressure of the active medium are comparatively low. Ben Khalifa and Thiery [1] investigated the minimum pressure that is required to enable convex forming. While machining AA1050A-H14 sheets with a thickness of 1 mm, the relatively low minimum pr
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