Abstract
Auxiliary systems for sheet forming processes are widely used to improve products accuracy and increase tools life. As example, in blanking hydraulic dampers are widely used to reduce shocks and vibrations; nitrogen springs are often integrated in deep drawing tools to correct the ram tilt or to locally increase the blank-holder force, obtaining geometrical features on the stamped blank with one press pass. In this paper, a Magneto-Rheological (MR) semi-active actuator is developed for sheet forming operations and the interaction between MR fluid and electromagnetic field is investigated by Finite Element (FE) analysis. To overcome the limitations of gas springs and hydraulic actuator, the static electromagnetic circuits is reconfigured with respect of conventional MR actuators known in the state-of-the-art. The novel MR actuator has an inner bore where the electric windings are placed, while the narrow gap, in which the active MR fluid flows, is obtained between the inner bore and the cylinder internal surface. The resulting magnetic fields H and induction fields B, as well as the selection of components materials, are studied through the magneto-static FE model. The results from FE simulations show a longer activation length along the gap resulting in higher controllable forces values, without increasing the overall dimensions of the proposed prototype.
Highlights
Several researches demonstrate the effectiveness of auxiliary systems to increase product accuracy and process robustness in sheet metal forming operations
Kishore et al [10] realize a MR damper to reduce tool vibrations during hard turning process. The aim of this works is the numerical validation of the design of a MR actuator for sheet metal stamping operations capable to overcome the limitations of hydraulic dampers and nitrogen gas springs
The paper presents the numerical design of a new MR actuator for sheet metal stamping operations, as alternative to the conventional auxiliary systems, i.e. hydraulic dampers and nitrogen gas springs
Summary
Several researches demonstrate the effectiveness of auxiliary systems to increase product accuracy and process robustness in sheet metal forming operations. Nitrogen gas springs are implemented to achieve a better control of blankholder force during deep drawing [3] and to create an “in-die” cushion [4]. These systems have intrinsic limitations, e.g. hydraulic dampers present short stroke and the nitrogen gas springs maximum force is available only at the end of the stroke. Kishore et al [10] realize a MR damper to reduce tool vibrations during hard turning process The aim of this works is the numerical validation of the design of a MR actuator for sheet metal stamping operations capable to overcome the limitations of hydraulic dampers and nitrogen gas springs.
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