Flow planning and control of single-stage multimachine systems
Abstract
The concept of single-stage multimachine systems (SSMS) has been introduced for newly emerging manufacturing environment which can be expressed by mass customization. In SSMS, the complete operations of a workpiece are performed on a machine tool in a single machine setup. SSMS are characterized by make-to-order manufacturing, unstable demands and a large variety of parts, tool movement policy, and no part routing between machines. The controlling focus of shop floor control functions in SSMS is to meet the variable customer's needs through flexibility and quick responsiveness. This thesis is motivated by the hypothesis that existing shop floor control methods using the hierarchical approach is irrelevant and/or unfavorable for SSMS because of its lack of flexibility, and its assumptions which do not represent the characteristics of SSMS. A non-hierarchical control scheme is presented whose basic idea is that the time of decision making is shifted such that more decisions are made in real time. Most of the pre-release problems are not addressed before the start of a production period, but they are incorporated in operational functions in which decisions are made based on dynamic shop floor status. The absence of pre-release planning decisions causes a number of part-machine matching alternatives (among which the best matching is made opportunistically) when a part release function is initiated, and hence allows manufacturing systems to respond quickly to the environment changes such as machine breakdown or demand changes. Tooling is a major resource constraint in SSMS under a dynamic tool sharing environment so that it plays a key role in the operational decisions. Once parts are loaded on machines, operation/tool selection decisions are initiated. Coordination of the operations (of several machines) in terms of tool requirements is a major consideration at this stage. A real-time operation selection algorithm is presented where the concept of product flexibility is incorporated. Simulation experiments are performed to verify the effectiveness and feasibility of the proposed control scheme and to compare the presented operational decision methods with existing approaches. This research also addresses tool requirement planning problems in SSMS.
Degree
Ph.D.
Advisors
Tanchoco, Purdue University.
Subject Area
Industrial engineering|Operations research
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