Scheduling and lot-sizing in the dairy industry: the yoghurt production case

Abstract

In this work, a continuous-time Mixed-Integer Linear Programming model (MILP) is developed for the short-term scheduling and lot-sizing problem in a multi-product yoghurt production line of a real-life dairy plant. The problem under question is mainly focused on the packaging stage considering though accurate timing and capacity constraints with respect to the fermentation stage. Packaging units are operating in parallel and share common resources. Sequence-dependent times and costs are explicitly taken into account and optimized by the proposed framework. Daily production line shut-down and setup times are also introduced, as a production policy to guarantee high quality of final products.

To the best of our knowledge, the proposed approach is the first systematic attempt to explicitly address all the aforementioned issues in tandem. Several cases of a large-scale Greek dairy plant have been considered using the proposed model. Solutions obtained are presented, criticized and assessed in a real industrial environment. A number of benefits due to the use of optimization-based techniques are revealed. Finally, concluding remarks are drawn.