Springback control and large skin manufacturing by high-speed vibration using electromagnetic forming

In this paper, a novel method of electromagnetic partitioning forming with elastic cushion is proposed. Its main principle is based on that the parts vibrate at high speed under the action of the electromagnetic force and the rebound force of the elastic pad. The state of the elastic parts inside the workpiece is changed into plastic state, and then, springback is eliminated through vibration. A common spiral coil is used to generate the magnetic field. A finite element model has been developed to analyze the effects of coil structure and coil discharge position on the stress, strain, and surface quality of the parts. It is found that a 1.5-mm bump is generated on the sheet surface, which corresponds to the middle of the coil. This is because this sheet region corresponds to the coil edges moving towards each other in opposite directions. Subsequently, the electromagnetic shielding method is used to isolate half of the spiral coil. Both the simulation and experiment demonstrated that no bulge was produced on the sheet surface. Moreover, the internal stress and springback of the parts are significantly reduced due to that the sheet vibrates at high speed. Large-scale skin was obtained after the coil was discharged multiple times in six different positions. Compared to traditional stretching, the springback of the parts is significantly reduced and the plate surface is smooth after electromagnetic forming. Consequently, the high-speed vibration induced by electromagnetic forming can reduce springback and enables the manufacturing of large size parts with smooth surface.