Scheduling parts in a combined production-transportation work cell

Helman Stern, Gad Vitner

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40 Scopus citations


This paper is concerned with a combined production-transportation scheduling problem. The problem comprises a simple, two-machine, automated manufacturing cell, which either stands alone or is a subunit of a complete flexible manufacturing system. The cell consists of two machines in series with a dedicated part-handling device such as a crane or robotic arm for transferring parts from the first machine to the second. The loading of a new piece on the first machine and the ejection of a finished piece from the second machine are performed by dedicated automated mechanisms. The introduction of parts into the system is done n at a time, whereby the parts are reshuffled into a sequence that minimizes completion time. All processing and transfer times are considered deterministic—a reasonable assumption for a cell comprising a robotic transfer device and two CNC machining units. What complicates the problem is the assumption of a non-negligible time for the transfer device to return (empty) from the second machine to the first. The operation is a generalization of a two-machine flowshop problem, and is formulated as a specially structured, asymmetric travelling salesman problem. An approximate polynomial time 0(n log n) algorithm is proffered. The procedure incorporates a lower bound using the Gilmore-Gomory algorithm for the no-wait, two-machine flowshop problem.

Original languageEnglish
Pages (from-to)625-632
Number of pages8
JournalJournal of the Operational Research Society
Issue number7
StatePublished - 1 Jan 1990


  • Algorithm
  • Flowshop
  • Production scheduling
  • Work cell


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