A Graph Representation Scheme for Process Planning of Machined Parts

A new generic graph representation scheme for process planning is presented. It has been specifically developed to facilitate the planning and control of geometric dimensions and tolerances. Relationships between cut, location, and datum surfaces and machining operations are represented by a graph consisting of connected boxes. A box is a multi-terminal node that corresponds to a machine set-up. Machining operations are depicted as arrows inside the box. These connect input nodes, representing datum and location surfaces, to output nodes, representing machined surfaces. External connectors join boxes together to form a directed graph. The main purpose of these connectors is to indicate the surfaces (from prior set-ups) that are used as location and datum surfaces for later set-ups. The representation covers cutting operations and non-cutting operations, such as surface finishes and coatings. The paper concludes with an example that illustrates the application and power of the scheme.