Title page for ETD etd-11292001-102749


Type of Document Master's Thesis
Author Wu, Yingxiang
URN etd-11292001-102749
Title Rapid Prototyping Job Scheduling Optimization
Degree Master of Science
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Bohn, Jan Helge Committee Chair
Myklebust, Arvid Committee Member
Sarin, Subhash C. Committee Member
Keywords
  • Solid Free-form Fabrication (SFF)
  • Fused Deposition Modeling (FDM)
  • Layered Manufacturing (LM)
  • branch and bound
  • machine idle time
Date of Defense 2001-11-16
Availability unrestricted
Abstract
Today's commercial rapid prototyping systems (i.e., solid freeform fabrication, layered manufacturing) rely on human intervention to load and unload build jobs. Hence, jobs are processed subject to both the machine's and the operator's schedules. In particular, first-in-first-out (FIFO) queuing of such systems will result in machine idle time whenever a build job has been completed and an operator is not available to unload that build job and start up the next one. These machine idle times can significantly affect the system throughput, and, hence, the effective cost rate.

This thesis addresses this problem by rearranging the job queue to minimizing the machine idle time, subject to the machine's and operator's schedules. This is achieved by employing a general branch-and-bound search method, that, for efficiency, reduces the search space by identifying contiguous sequences and avoiding reshuffling of those sequences during the branching procedure. The effectiveness of this job scheduling optimization has been demonstrated using a sequence of 30 jobs extracted from the usage log for the FDM 1600 rapid prototyping system in the Department of Mechanical Engineering at Virginia Tech.

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