Equipment scheduling problem under disruptions in mail processing and distribution centres

This paper addresses the production and workforce scheduling problem under disruptions in United States Postal Service mail processing facilities. These facilities contain a large variety of equipment and employ a non-homogeneous workforce that work on shifts of various lengths and start times. Disruptions such as demand fluctuation and absenteeism happen and may significantly change demand and the size of workforce. How to adjust production plans and workforce schedules through the use of overtime and flexible employees in the face of these disruptions to meet the service commitment is a challenging problem yet to be solved. This problem is modelled as a large-scale integer program, which contains equipment scheduling, shift scheduling and overtime management, and break assignment modules. Problems of realistic size are solved efficiently through an LP-based decomposition algorithm. Comprehensive experiments have been designed to investigate the effects of the use of overtime, the control of absenteeism, and the importance of integrating equipment and workforce scheduling simultaneously. The model integrates seamlessly with other research studies and provides the necessary and critical tools to manage the resources in a facility on a routine basis.