n-Cyclic Hoist Scheduling Problem to manufacture more than 2 products

Abstract

Jobs of more than two products (n>2) must be manufactured in a production line of tanks. A hoist transports the jobs between tanks. If the size of both batches is equal and the number of jobs is high, a cyclic scheduling can be proposed. The problem consists in the scheduling of hoist movements, which is known as CHSP (Cyclic Hoist Scheduling Problem). The objective is double: first, determine a sequence of the n products in a job cycle and then minimise the cycle time for the given sequence of products (n-cycle). We propose the use of a branch-and-bound procedure previously developed, which was developed for the 2-cycle. As there are different sequences of products, the experience demonstrates that the use of upper bounds as a result of previous steps in the algorithms generally leads to the optimum solution in lower times.