Development of the hole position's minimum distance calculation in the L-die bending process

Abstract

Currently, several L-shaped bent part assemblies based on the hole assembly methods are being widely employed. Consequently, it is crucial to determine the hole position precisely and without distortion after bending. Although determining the minimum distance of the hole location (d_min) can help prevent hole distortion during the L-die bending process for hole diameter < 25 mm, d_min = 2t + r, and hole diameter ≥ 25 mm, d_min = 2.5t + r, where t = workpiece thickness and r = tool radius or bend radius. However, these determinations cannot be determined with accuracy. A main challenge in the current study is figuring out whether d_min is appropriate for the L-die bending process. Laboratory experiments and finite element analyses were used address this challenge. In contrast to previous formulas, the new d_min determination does not consider the workpiece thickness and bend radius as suggested in the past alone, but also the bend angle is mainly considered. Therefore, the suggested d_min determination in the past are overly specific, especially for bend angles greater than 90°. Application of the proposed formula decreases the error by approximately 33% and 65% during the determination of the minimum distance of hole in the cases of 120° and 150° bend angles, respectively. Therefore, it is imperative to define d_min in the L-die bending process to obtain the requisite accurate hole locations after bending, and the use of developed d_min is strictly recommended, especially for bend angles greater than 90°.