Spring-back effect during multi-pass bending of sheet blanks

Abstract

A significant factor, which leads to the discrepancy of the final sizes of the bent sheet parts to their drawings is the springing of the sheet blank during bending. At the same time, the springing during multi-pass bending is not sufficiently studied. The purpose of the work is to obtain the graphical and mathematical dependencies for descriptions of the resultative spring-back angle of the blanks at the multi-pass bending, taking into account the width of the blank, number of passes, and pre-bending angle at each preliminary pass. The paper describes the basic information about the difference between the spring-back angle for one-pass or multi-pass bending. In the course of the study it is shown that during calculations of forming and preventive prediction of the geometric quality of bending shapes it is necessary to take into account properties of the blank material, as well as the angles of the prebends and the width to thickness ratio of the blank. A methodology of experimental research was developed for determining the spring-back angle during multi-pass bending in three bending dies with 109°, 91° and 72° pass-by-pass reducing angles.