Deriving the detailed machine schedule from a weekly MRP requirement

In this paper we present a mould shop scheduler (MSS) that was developed for the Moulding Division at a major US telecommunications equipment manufacturer. This plant consists of close to 100 injection-moulding machines, and over 1000 different moulds are used to manufacture more than 1500 different parts. The MSS procedure reads the MRP orders at the start of each week, and then generates for each machine the sequence of parts or orders to be processed, the production quantity, and the sequence of mould and material changeovers. The MRP orders are generated by a corporate system that is responsible for plant-wide scheduling. In developing the daily schedule, the objectives of the MSS procedure are to: (i) reduce the total time spent on setups; and (ii) minimize the inventory of finished parts. The MSS procedure consists of four heuristic algorithms that are sequentially solved. The use of the algorithms is illustrated by an example, and a comparison with a lot-for-lot MRP implementation is shown.