Control of springback in a flanging operation

Abstract

A “double-bend” technique has been developed for the control of springback in a simple flange operation. A series of steels, whose strength varied from 207 MPa (30 ksi) to 1240 MPa (180 ksi) were evaluated. For ratios of material thickness to bend radii greater than 0.2, it was found that the limiting state was 2 to 3 deg negative springback; however, the higher the strength of the steel, the more the specimen had to be moved between making the bends. The limiting value of the springback is independent of the flow stress of the material; with one die configuration it was possible to obtain approximately 0 deg springback in a flange, even though the flow stress of steels investigated varied from 207 MPa (30 ksi) to 896 MPa (130 ksi). In addition, the use of a single tapered die, which changed the position of the bend continuously during the test, also was shown to produce some reduction in springback.