Geometric reasoning for manufacturability evaluation--application to powder metallurgy

Abstract A new approach to perform geometric reasoning for manufacturability evaluation is developed using three-dimensional objects that are based on a process-dependent geometric model. It is demonstrated that by incorporating the limitations of the process directly in the geometric representation scheme, the task of manufacturability evaluation becomes straightforward and can be performed without either feature extraction or designing with features. The new approach is illustrated for the cold die compaction of powdered metals (PM). The geometric model for PM consists of a set of fundamental three-dimensional manufacturable entities, plates, blind cavities, and through cavities, all of arbitrary shape. The new approach is further enhanced by using a single, compact data structure that captures the shape characteristics to fully define the PM parts, and to support the reasoning required for manufacturability evaluation. Using this approach provides the ability to perform geometric reasoning easily that: (1) determines a part's orientation and tooling; (2) identifies sharp corners, feathered edges, thin walls, grooves, shelves, and notches, and other part attributes that adversely affect die fill, tooling cost and life, part integrity, and density control; and (3) automatically adds fillets, chamfers, edge rounds, tapers, and axial flats, which are common to PM parts. Furthermore, the reasoning is performed using a small set of algorithms to manipulate the appropriate information in the data structure, and is sufficiently robust to account for all practical shapes. The close coupling of the data structure and the algorithms permits the evaluation and modifications to take only a few seconds on a 486-based personal computer, and therefore, are performed in real time as the parts are created.