Sequence planning for bending operations in progressive dies

Abstract

This paper aims to study the use of the superimposition scheme to quickly plan the bending sequence in a progressive die design for a sheet metal part which contains bending and shearing features, and to determine the best among multiple feasible solutions. The biggest problem in applying superimposition is that the possible solutions form an excessive solution space when multiple punches are used. In order to solve this problem, this paper introduces three steps: strip preparation, punch layout, and layout evaluation. The punch layout uses clustering rules to classify punches into five groups: prior use (the punches must be used first), posterior use (must be used last), simultaneous use (must be used together), sequential use (certain punches must precede others), and exclusive use (must not be used together). It then derives the compatible sets for each punch, followed by an expansion of the number of punches and punch layout, in order to obtain every feasible solution. The layout evaluation adopts a multiple-criteria decision-making (MCDM) model with a scoring function to analyse every feasible solution and determine the best sequencing plans. The scoring function used is based on the following four criteria: number of stages, moment balancing, strip stability, and feeding height. In the conclusion, this paper builds up a pilot system and demonstrates how the method can generate bending sequences and produce strips.