An incremental flanging strategy for small hole with electropermanent magnetic device.

Within the manufacturing industry, hole flanging is an essential process for forming local features in sheet metal. To enhance the flanging height, the diameter of the prefabricated hole should be reduced. However, the undersized diameter of the hole may result in a crack during the flanging process. Combining the electropermanent magnet (EPM) technique with the stamping process, a composite flanging method with incremental feed is proposed to improve sheet forming performance based on the superposition principle of magnetic circuits. Through a symmetric flanging model, the thickness distribution, contour, and forming height of flanging zones are simulated, measured, and found to be reasonably consistent with related theories. The results show that the built model is suitable for investigating flanging deformation behavior. Flanging processing was performed on 304 stainless steel plates with various laser cutting predrilled hole radii. Under various increment rates, the flanging inclination angle is measured and compared through finite element method (FEM) and experiment. Furthermore, when the plate thickness ratio to the prefabricated hole diameter is 0.11, the limit circular hole flanging coefficient can reach 2.22, which is an improvement of 4.83% compared to the traditional flanging process. [ABSTRACT FROM AUTHOR]