Methods for the sequencing of sheet metal bending operations

The sequencing of part set-ups, in the context of design verification or process planning activities for sheet metal bending operations, is a rather complex combinatorial problem. The verification of the feasibility and the acceptability of a single bend set-up requires CPU-time consuming operations, e.g. collision checking and a manipulation requirement analysis. For more complex parts, and thus increased numbers of bends, exhaustive search methods can therefore not be applied in a time-economic way. Although the identification of an optimal sequence may not always be possible, a number of techniques can be applied to significantly downscale the problem size. Several complementary approaches have been worked out to proceed in identifying near-optimum feasible bend sequences. Constraint solving and branch-and-bound techniques are used to identify interesting potential solutions. The reported branch-and-bound search method is characterized by a dynamically updated penalty system, that reflects the manufacturing knowledge obtained through analysis of partial sequences. A case study is used to illustrate the effectiveness of the applied search procedures.