A heuristic algorithm for two-stage flexible flow shop scheduling with head group constraint.

On the background of the shops in the mould manufacturers, in this paper, a two-stage flexible flow shop scheduling problem is first described to minimise the makespan with head group constraint and released time, where the first stage consists of unrelated parallel work centres. Next, this problem is proved to be NP-hard. After that, a constructive heuristic algorithm, named as H′, is proposed and then both its time complexity and worst-case bound are analysed in detail. In addition, three classical heuristics are improved for the solution of this problem and their time complexity is also given. In order to test the efficiency of the H′ algorithm, sets of instances are designed. Compared with the three improved heuristics by means of these sets of examples, the performance of the H′ algorithm is superior. Furthermore, the H′ algorithm can even solve large-size practical problems in a reasonable solution time, which is significant to the application in the shops of mould makers. [ABSTRACT FROM PUBLISHER]