Chemical Engineering Science, Vol.167, 251-264, 2017
Simultaneous 2D hoist scheduling and production line design for multi-recipe and multi-stage material handling processes
Multi-recipe and Multi-stage Material Handling (M3H) processes are broadly employed in various industries, where hoists are used for job transfer among different processing units. The hoist movement should be optimally scheduled to maximize the production efficiency. In previous studies, the hoist scheduling is based on a given one dimensional (1D) M3H production line, where spatial locations of processing units are already fixed. Such an arrangement totally separates the hoist scheduling from the optimal design of M3H processes and wastes lots of hoist traveling time on job transfer, so that the production efficiency is inherently restricted. In this paper, a novel cyclic hoist scheduling (CHS) method coupling the optimal design of two-dimensional (2D) production line has been developed for the maximum production efficiency of general M3H processes. It can maximize the production efficiency by simultaneously and optimally determining: (i) the hoist movement schedule for handling different types of jobs with different processing recipes; (ii) the allocation of different processing units in optimal 2D spatial locations; and (iii) the assignment of multi-processing capacity to most needed processing units. The developed method also considers tough processing constraints such as the customized production ratio and various processing time limits for every job in each processing units. The efficacy of the developed method has been demonstrated by case studies. (C) 2017 Elsevier Ltd. All rights reserved.