(599ac) Simultaneous Hoist Scheduling and 2D Production Line Design for Multi-Stage Material Handling

Multi-stage material handling (MSMH) processes are broadly used in industries for manufacturing massive amount of products/workpieces (jobs).  A hoist is a controlled device for manufacturing by following a preset movement schedule, including job lifting, releasing, and moving along a production line.  In previous works, how to feasibly and timely organize hoist schedules has been broadly studied.  However, the productivity of an MSMH process not only depends on hoist movement schedule, but also substantially relies on the production line arrangement, i.e., the design for spatial allocations of various processing units. This is because a hoist needs to travel among processing units to pick up or drop different jobs for different processing purposes, and such travelling time greatly depends on unit spatial allocations, which affects both job processing and change-over time. Thus, the production line arrangement and hoist scheduling are better to be considered simultaneously for the best performance of a hoist-employed multi-stage material handling process. 

In this paper, an MILP model has been developed to couple cyclic hoist scheduling and 2D production line arrangement for the maximum productivity of a general MSMH process.  The major advantage of this study is that the spatial allocation of processing units and hoist movements of a 2D production line have more options than those of a traditional 1D production line, so that its productivity has better chance to be improved significantly.  The efficacy of the proposed methodology is demonstrated by a case study.  The comparisons between 1D and 2D production line arrangements have also been conducted.