The parallel machine scheduling problem with variable demand and a pre‐defined lot size

In this paper, we consider the problem of scheduling multiple product types in parallel machines given variable demand across a multi‐period planning horizon. Production is organised around a pre‐defined lot size as frequently arises in the pharmaceutical industry. The problem class falls within the big bucket category with a single level of production, it is capacitated and considers multiple parallel machines. There is no deterioration of the items within the planning horizon, the demand is dynamic and deterministic. A complex set‐up structure is assumed, and backordering is allowed. The objective is to find a production schedule that minimises holding, setup and backordering costs. Four heuristics are developed to generate the production plan. Computational experiments demonstrate that the solutions generated are close to optimal for small problems, and that the methods have robust performance for larger problems.