Planning and scheduling of a parallel-machine production system subject to disruptions and physical distancing

This paper aims to quantify the effects of production disruptions and physical distancing constraints due to the pandemic in a parallel-machine production environment. The machines are non-identical and are utilized for producing a finite set of jobs (parts) in a plastic injection molding production. The production process is subject to random production downtime disruptions. A mixed-integer linear programming (MILP) model is developed for optimizing the joint production plan and schedule, which maximizes the production’s total benefit. The model is utilized to plan and schedule a set of 17 machines in a Canadian manufacturing company. To explore the effects of physical distancing and production disruptions on the production’s total net profit, four different scenarios for normal operation and production during the pandemic, with and without production downtimes, are considered. A genetic algorithm is utilized to solve the model. The results show that considering machines’ random breakdowns and physical distancing individually reduces the total profit of the production by 71.58% and 57.98%, respectively; while their joint effect results in a 88.54% reduction in the annual net profit.