A novel actuator for precise design of the spatial-distributed Lorentz force in electromagnetic sheet metal forming: process principle, optimization methodology, and experimental validation

This paper introduces a novel special-structure field shaper actuator designed to achieve precise spatial distribution of the Lorentz force in electromagnetic sheet metal forming. By precisely designing the bottom profile of the field shaper, the generated Lorentz forces on the workpiece can be controlled to meet various forming requirements. Moreover, the actuator incorporates multiple solenoid field coils to compensate for energy loss in the field shaper, effectively multiplying the input energy. The use of solenoid-type field coils allows for decoupling the optimization of system inductance from the design of the Lorentz force distribution, simplifying the reinforcement of the field coils and enhancing the limit input energy. The paper presents the analytical working principle and control rules to achieve the desired Lorentz force distribution and system inductance. Furthermore, a detailed design method based on numerical simulations is demonstrated to improve forming profiles and uniformity in thin-walled shell part forming. The simulation results indicate that the optimized actuator can reduce the radial thinning variance and the maximum thinning rate by 85% and 35%, respectively. The feasibility of the actuator and design method is verified through a series of comparison experiments, which exhibit a significant reduction in the maximum thinning rate (from 18 to 12%). This research represents a promising advancement in electromagnetic sheet metal forming, offering improved forming capabilities compared to conventional actuators.