A feature modification framework for the generation of alternative process plans

Abstract

This paper proposes a feature modification framework for the generation of alternative process plans. In process planning, feature modification is not unique for the following reasons. First, feature interaction and multiple feature interpretation generate alternative machining features. Second, setup planning generates alternative setups. Alternative setup plans make machining features not unique. Third, the shape of a machining feature can vary according to the operation selection. In the proposed frameworkl these alternatives are used in the modification of alternative machining features. The feature modification is performed in three steps. These steps are geometry oriented decomposition, setup oriented decomposition and operation oriented decomposition. The relationship between modified machining features is represented by an AND/OR graph. In the geometry oriented decomposition, the total machining volume is divided into the machining features using a scan-line algorithm. The multiple interpretation and geometric interaction of the features are resolved in this step. In the setup oriented decomposition, alternative setups are investigated. Tolerance relationships and machining stability are considered. Grouping and division of machining features are performed according to the tool access direction. Alternative machining methods are examined for a machining feature. The division of machining features is performed when necessary. Finally, alternative machining feature sets are represented by an AND/OR graph data structure. They are used in the generation of alternative process plans. The effectiveness of the proposed algorithm is demonstrated by examples.