(556d) Optimization of Two-Dimensional Hoist Scheduling and Production Line Design for Multi-Stage Material Handling

Multi-stage material handling (MSMH) process is widely applied in industries to manufacture large amount of various workpieces and products (jobs). Generally, a hoist will handle all jobs by following a preset movement schedule, including job lifting, releasing and moving along a production line. Different scheduling can cause huge difference in production period. Therefore, lots of engineers have studied the feasibility and optimization of hoist movement schedules. However, the design of production line, such as the spatial allocation of every processing unit, could also affect the production rate. During the production, hoist will travel forth and back to pick up job from its current unit and release it into the next one, following its processing requirement. In this way, a proper arrangement of unit position would dramatically shorten the total moving time and improve the processing capability.

In this paper, a new two-dimensional (2D) matrix arrangement of processing unit has been proposed to replace original one-dimensional (1D) line arrangement for the optimization of productivity, and a mixed integer linear programming (MILP) model has been developed to solve this problem. The major advantage of this study is that the compacted allocation provides shorter paths for hoist to move, so the productivity could 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.