An artificial bee colony algorithm for a two-stage hybrid flowshop scheduling problem with multilevel product structures and requirement operations

Real world final products have almost multilevel structures, where different items are assembled together according to predefined bill of materials. Also, each item must experience a set of processes before assembly according to a given precedence relation between the processes. This paper considers a hybrid flowshop with two stages for processing on items and assembling final products. The first stage is dedicated to processing on items and consists of some non-identical parallel machines. After finishing processing on the items on the first stage, assembly of items into final products starts at the second stage. The production manager desires to minimise the maximum completion time (i.e. makespan). Then, the problem is modelled as an integer linear program and is solved by Lingo. As the problem is NP-hard, an artificial bee colony algorithm along with a genetic algorithm is developed to obtain near-optimal solutions in reasonable run-times. Further, efficiency of the solution methods is examined on different problem instances.