Research On Incremental Electromagnetic-assisted Stamping With Multidirection Magnetic Pressure And Coil-less Electromagnetic Forming

A new forming method named cylindrical cup incremental composite deep drawing with radial magnetic force pushing is proposed. Material in the region of flange can be pushed inward the die cavity under the magnetic force generated by the coils, so the forming method can improve deep drawing forming limit.The numerical simulation results show that after discharging of the coils, bulge forming can be seen in die fillet area of the blank. The result proves the feasibility of the forming method. The simulation results also show that coils of concentric shape is better than coils of spiral shape in improving the forming uniformity; with the increase of the number of coil turns in flange region, the bulge height is bigger, but forming uniformity get worse; increasing distance between turns of coil, the bulge height and energy efficiency reduce.The experimental results coincide with the numerical results.Comparing with the traditional drawing process, the forming depth is increased by 19.2% if the coil discharging for one time, while the forming depth can be increased by 45.1% and the deformed blank diameter greatly reduces if the coil discharging for four times.Coil-less electromagnetic forming process is also proposed in this paper. The process applies the electricity flow in the blank directly, and simultaneously inducing a current in the copper. electromagnetic force between the tow currents makes the blank forming.The FEM simulation results of the coil-less electromagnetic bulging of sheet forming process show that the distribution of currents is uneven if appling the electricity flow in the blank directly, and the blank forming shape is an inverted saddle. Using stepped circular copper, electromagnetic force near the discharge electrode is reduced and the blank forming shape becomes a strip in current direction. While using stepped oval copper, further reducing electromagnetic force near the discharge electrode, the forming is uniform but maximum height decreases 19.6%. compareing with the results using stepped circular copper.The FEM simulation results of the coil-less electromagnetic forming of large blank show that current is mainly located between the discharge electrodes and forming shape is uneven. By using arc-shaped electrodes,when the angle is 90°, there is the most uniform current distribution in the region, forming results are best, but forming height is minimum. When changing arc-shaped electrodes into groups of small discharge electrodes,and when using 3 pairs of electrodes, current density distribution is the most uniform, and forming high imcreases 8.2% comparing with the results of 90° arc electrodes.