Retaining flexibility in process planning: Applications to shape deposition manufacturing.

摘要

Manufacturing processes work following a process plan to transform raw material into a finished product. Traditionally, process plans consist of a totally ordered set of operations to be performed. In many instances, total ordering of the component operations is not required by technological reasons but rather adopted for operational reasons of economy of information handling and decision making on the shop floor. This economy, while adequate until present times, is no longer necessary in the presence of ubiquitous and inexpensive processing power and communications.; This thesis proposes an approach to process plans that retain flow management flexibility on the shop floor. It relates the required operations to perform in a partial order, opening the possibility to implement opportunistic scheduling and to exploit dynamic alternate routing in the shop.; This thesis will show how this approach can achieve significant improvements in shop throughput and cycle time. The technique has been applied to Shape Deposition Manufacturing (SDM), a novel Rapid Prototyping process developed at Stanford University and Carnegie Mellon University. The work presented here shows how partial order plans can be generated from CAD descriptions, and quantifies the achievable improvements in shop throughput and cycle time for a model of the SDM process.; The contributions of this thesis are: (a) to formalize the notion of flexible process plans and their application to Shape Deposition Manufacturing, (b) show how this flexibility can be used in improving shop performance, and (c) develop formal models of the SDM process and the manufacturing shops that implement the process.