tool selection and dimensional accuracy verification for sheet metal bending

Sheet metal products are widely used in various industries nowadays. Among those, bent parts are made by performing linear bends on the sheet metal blanks prepared according to the unfolding of the corresponding designs. Process planning for bent parts consists of closely related tasks, such as unfolding generation, operation parameters and tool selection, bend sequencing and tolerance verification. Aiming at an automated process planning system (CAPP) for bent parts, the aspects of tool selection and dimensional accuracy verification have been tackled in this study. Regarding the aspect of tool selection, due to the requirements in the industry, both part complexity and tool variety for bending have increased. This fact hinders the use of simple Group Technology in mapping compatible and collision-free tools to bend lines merely based on part descriptions. Meanwhile, the interrelation between tool selection and bend sequencing makes automated tool selection a combinatorial problem. In this context, reactive approaches in tool selection, such as open selection during bend sequencing or selection based on a predefined bend sequence, cannot provide feasible tool solutions within an acceptable time span. The current research has resulted in a proactive strategy to downscale the problem complexity. According to this strategy, tools are preselected based on the analysis of part geometries. By detecting collision prone details residing in bent parts, collision scenarios are identified for this preselection step. Furthermore, the initially selected tools are refined according to the collisions detected while planning for a bend sequence. A generic approach is proposed for tool selection based on the evaluation of the encountered collision scenarios. Such collision scenarios are predicted based on either the envisaged part geometry or the intermediate part shapes calculated respectively in the preselection or the refined selection phases. Applying the developed methods for analysing the part and tool geometries in the process, the algorithms proposed for the tool selection procedure in this study are able to swiftly identify the potentially feasible tools for the foreseen collision scenarios. Subsequently, a set of rules has been composed and can be selectively triggered to identify the requirements for the tool parameters to overcome the different collision scenarios.