Knowledge-based sequence planning of shearing operations in progressive dies

Abstract

This paper aims to study the methodology of building the knowledge of planning adequate punches in order to complete the task of strip layout for shearing processes, using progressive dies. The usage of superimposition of punches for planning strip layout is widely accepted among progressive die designers; however the huge number of combinations of punches may turn this easy-to-understand process into a nightmare. The proposed methodology uses die design rules and characteristics of different types of punches to classify them into five groups: prior use (the punches must be used first), posterior use (must be used last), compatible use (may be used together), sequential use (certain punches must precede some others), and simultaneous use (must be used together). With these five groups of punches, the searching space of feasible designs will be greatly reduced, and superimposition becomes a more effective method of punch layout. The superimposition scheme may generate many feasible solutions. Although none of them really violates die design rules, some of them are just better than others. An evaluation function based on number of stages, moment balancing and strip stability is developed. For meeting different designers' preferences, these three factors are coupled with various weightings, so, designers can fine tune and find better results. The whole process is not only to provide a new approach to solving the superimposition puzzles, but also to try to integrate the die design rules and designer's personal experience, which should be extremely helpful in speedier progressive die design.

Programming for evaluating strip layout of progressive dies

“…9(b) Fig. 9 Solid models: (a) sheet metal part, (b) shearing punches P i and bending punches B i First, the feasible layouts, which are satisfied die design rules, for this part are determined manually based on the scheme suggested by [6]. Next, the Pro/Web.Link application is utilized as an automatic tool for evaluating 12 feasible layouts of the sample part.…”

“…After obtaining center of the equivalent reaction force ( ) and center of the die ( ); the following equations [6] are employed to calculate maximum deviation and the real deviation of the center of equivalent reaction force with respect to the center of the die (as shown in Fig. 11(b)): Finally, the following equation [6] is used to determine moment balancing factor F b :…”

“…Among many factors in planning strip layouts that affect the cost and quality of progressive die, four factors had proposed by Lin and Sheu [6] for layout evaluation function; they are: station number factor , moment balancing factor , strip stability factor and feed height factor. The evaluation score is computed based on these four factors: These four weighting factors are chosen by the designers who determine how much important each factor contributes to the strip layout evaluation.…”

“…Their solution, nonetheless, only dues with shearing operations. The research presented in is paper is the succeeding project of [6] and it proposes a proper solution for automatically evaluating feasible strip layouts in progressive dies from their 3D models. The solution helps designers quickly fine tune and choose better results among many feasible layouts.…”

“…Unfortunately, there are, in general, more than 8 punches in practical cases. Lin and Dean [6] suggested a modified scheme of exhaustive search and punch grouping rules so as to find all the feasible layouts with eliminating unwanted searching paths. They also proposed an evaluation function for ranking feasible strip layouts in term of station number, moment balancing and strip stability.…”