Flexible Tooling Enabled by the Electromagnetics With Discrete Blank Holding Force: Short-Time Pulse Control and Forming Validation

The increasing demand for higher precision in complex surface forming has highlighted the significance of utilizing variable blank holding force (VBHF) in segmented blank holding. However, applying electromagnetic blank holding in such segmented systems remains unexplored, presenting a critical challenge in continuous forming processes. This study proposed an innovative, flexible tooling system driven by an electrically controlled permanent magnet, enabling discrete control of blank holders. An equivalent magnetic circuit for a single magnetic pole was developed alongside a model to characterize variations in electromagnetic force. The discrete VBHF control with a short-time pulse leverages the operating point migration law of the magnet, elucidating the control mechanism of discrete electromagnetic forces. An electrical-magnetic-mechanical coupling simulation model was established using Simulink, Simplorer, and Maxwell. The simulation results reveal that the control error of electromagnetic force across different blank holding areas under varying currents ranges from 0.1% to 1.7%, with a steady-state control error under any electromagnetic force curve remaining within 5%. Electromagnetic blank holding experiments on a car-door prototype demonstrated that the control error of discrete electromagnetic forces is between −50 N and 20 N. Applying short-time pulse current in VBHF loading also ensures forming quality while reducing continuous current consumption by 14.03% and decreasing hydraulic press tonnage demand by 14%. This study provides theoretical and methodological support for designing equipment that enables low-tonnage, high-precision continuous forming of complex surfaces.