Applying different control approaches for resources with high and low utilisation: a case study of the production of complex products with stochastic processing times

Research on dispatching rules has mainly focused upon deterministic job shop situations or small assembly environments and has ignored operational factors. Recent work has examined the relative performance of dispatching rules in companies that produce several families of complex products with stochastic processing times. Previous work has used common control policies for all resources. In practice, it is common for there to be a wide variation in the utilisation of machines. The Optimised Production Technology (OPT) philosophy suggests that particular attention should be paid to bottleneck resources. This paper investigates the effect of applying different manufacturing control approaches for resources with high and low utilisation. The work uses data obtained from an Engineer-To-Order (ETO) capital goods company that produces complex products in low volume. Processing times are assumed to be normally distributed. A range of scenarios are considered in which an increasing proportion of resources are considered to be 'bottlenecks'. The results show that the mean tardiness of products decreases significantly when the highly utilised machines are carefully controlled. However, there is only marginal benefit in carefully controlling the other machines.