Browsing by Subject "Total Completion Time"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    ItemOpen Access
    Parallel machine scheduling subject to machine availability constraints
    (2006) Sevindik, Kaya
    Within a planning horizon, machines may become unavailable due to unexpected breakdowns or pre-scheduled activities. A realistic approach in constructing the production schedule should explicitly take into account such periods of unavailability. This study addresses the parallel machine-scheduling problem subject to availability constraints on each machine. The objectives of minimizing the total completion time and minimizing the maximum completion time are studied. The problems with both objectives are known to be NP-hard. We develop an exact branch-and-bound procedure and propose three heuristic algorithms for the total completion time problem. Similarly, we propose exact and approximation algorithms also for the maximum completion time problem. All proposed algorithms are tested through extensive computational experimentation, and several insights are provided based on computational results.
  • Thumbnail Image
    ItemOpen Access
    Scheduling with tool changes to minimize total completion time under controllable machining conditions
    (2001) Köylü, Rabia
    In the literature, scheduling models ignore the unavailability of the cutting tools. Tool management literature considers tool loading problem when tools change due to part mix. In practice, tools are changed more often due to tool wear. The studies on tool management issues consider machining conditions as constant values. In fact, it is possible to change the processing time and tool usage rate of a job by changing the machining conditions. However, the machining conditions, such as cutting speed and feed rate e ect the processing time and usage rate of the tool in opposite directions. Increasing the usage rates of jobs will lead to an increase in number of tool switches. Processing times and number of tool switches are two components of our ob jective function. This two-side e ect creates a tradeo between processing time and tool usage rate. Therefore machining conditions should be selected appropriately in order to minimize the total completion time. We proposed a set of single-pass dispatching rules and a local search algorithm to determine the machine conditions for each job and to schedule them on a single CNC machine simultaneously to minimize the total completion time.