Design of roll profile in shape rolling of an irregular angle bar by the modified butterfly method

The roll profile of an angle bar is generally designed by the butterfly method however, the design of the roll profile of an irregular angle bar requires a special rule to take a tapered leg or a protrusion on the leg into account. For this purpose, the butterfly method has been modified in this study to design the roll profile for an irregular angle bar by introducing the equivalent leg thickness. The thickness of the tapered leg or the leg with the protrusion is changed into the equivalent leg thickness to calculate the thickness and length of the leg for the next pass. Shape rolling processes for inverted and unequal angle bars are designed by the proposed method, and its effectiveness is verified by FE-simulation and experiments using plasticine. In addition, the design method is applied to the shape rolling of more complicated irregular angle bar, such as an automotive door hinge. The cross-sectional shapes at each pass are compared with those obtained from the experiment using steel. The results of FE-simulation and experiment show that the proposed design method effectively designs the roll profile for an irregular angle bar, leading to accurate shape and dimensions in the final product within the allowable tolerance of ± 0.4 mm in thickness and ± 1.5 mm in length. Therefore, the proposed design method can be widely used to design roll profiles for variously shaped angle bars in industrial fields.