| Despite over two decades of research, computer integrated manufacturing has remained an elusive goal for conventional machining processes. This thesis describes some theoretical and practical issues in integrating feature-based CAD with CAM in milling. The immediate practical consequences of this research are the ability to do design for manufacture and automated rapid prototyping by machining for the first time. Previous attempts at integration have been only partially successful because standard planning techniques are not powerful enough to handle the requirements of milling. The integration strategy presented here is based on a new, synergistic approach to design, process planning and fixturing. Specific points of discussion in this thesis include: (1) A manufacturing-feature based design methodology called constrained destructive solid geometry (CDSG). CDSG is a way to ensure accessibility for each feature as it is entered into the system. (2) A model of the general process planning problem for machining. We highlight a class of feature interactions, called global interactions, as the most significant cause of planning complexity. A central idea in this thesis is the elimination of global interactions through hardware innovation and judicious software strategy. (3) A new universal fixturing technology called reference free part encapsulation (RFPE). RFPE makes it possible to machine parts of almost arbitrary shape with little fixture planning. RFPE eliminates the two most important sources of global interactions: fixturing and part rigidity concerns. (4) Algorithms for process planning. The efficiency of a manufacturing plan is a function of the number of setups, tool changes and cutting time involved. We discuss ways to improve the efficiency of the process plan without compromising the quality of the manufactured component. (5) A study of incremental process planning. We discuss how CDSG can be combined with incremental process planning to promote design for manufacture. We identify certain intrinsic properties of systems that are amenable to incremental analysis, and show that the system described in this thesis satisfies these properties. (6) A scheme for networked process planning. We discuss ways to link a designer with multiple remote machine shops simultaneously.; The methodologies outlined in this thesis have been implemented to create an experimental test-bed for rapid part realization. We outline the implementation and describe some design-through-manufacture experiments. |
