Flange forming with combined blanking and extrusion process on sheet metals by FEM and experiments

Abstract

Flange height and lip thickness are generally restricted by the formability of sheet metals in the conventional forming operation. Fracture can easily occur on the edge of the flange, causing it to fold and affecting the sustainability of the application of flange. In the current work, combined blanking and cold extrusion process is applied to manufacture component with the aim to obtain the substantial flange suitable for subsequent assembly with its counterparts. Meanwhile, FEM software DEFORM is utilized to simulate this process and to reveal the deforming features of the combined process and the accuracy of the simulation is experimentally verified. Both the results of simulation and experiment prove that fracture of flange forming mainly occurs in the cutting edge of punch die, which can be predicted by FEM simulation and can be eliminated or avoided by the three following methods: (1) the punch die is modified in the rounded corner of the die as a chamfer connecting the rounded corner and the punch head in an attempt to reduce the flow resistance of the raw material and solve the fracture problem. (2) Sufficient counter-pressure should be applied to bring about the hydrostatic pressure, causing the shear zone to become compressive (negative), and this leads to improvement of ductility of the sheet metals and can restrain fracturing. (3) Suitable combination of blanking and extrusion process should be arranged. Finally, the high-quality components are successfully manufactured through experiment, which confirms that the result of FEM simulation is correct and lays a technical foundation for the design of combined blanking and cold extrusion process on sheet metals.