Recognition of minimal feature covers of prismatic objects: A prelude to automated process planning

A comprehensive process planning automation system is developed to determine the minimum sets of product features that should be explicitly manufactured in the production of a product. We develop a cover set model (CSM) of the set of features to be produced in the automated planning of a production process. The CSM system advances the super relation graph (SRG) based system of Kao (1992) to provide a comprehensive process planning framework. This framework starts from the recognition of the elemental features ofa product from a description of its design provided by CAD systems and leads to the determination of the minimum sets of features required to produce a product. The proposed system consists of four phases: perfect feature creation (PFC), solid feature creation (SFC), cover sets determination (CSD), and minimum cover sets determination (MCS). In the PFC phase, each elemental feature that is not perfect is transformed into an equivalent perfect feature. In the SFC phase, the set of solid features constituting the product is generated from the elemental features. A solid feature is defined as a feature that can be produced by a single machining operation. In the CSD phase, a feature is classified into either essential or non-essential, and the cover sets for each nonessential feature are determined. In the MCS phase, the minimum cover sets are generated by cover concepts derived from the parsimonious covering theory. Illustrative examples along with an assessment of the computational performance of the proposed system are provided. The cover sets provide the set of feasible and sufficient production alternatives in manufacturing a product. The development of optimal production plans and the corresponding processing schedules from the results of the CSM is the next stage of this work.