Energy-efficient production scheduling considering outsourced manufacturing and tardiness cost

This paper focuses on a new energy-conscious parallel-machine scheduling problem with non-identical job due dates, considering outsourcing and transportation. The objective is to minimize the total costs of outsourcing, energy consumption, tardiness, and transportation. A mixed-integer linear programming (MILP) model is formulated to mathematically describe the understudied problem. Then the validity of the proposed model is tested by CPLEX using a set of practice-based randomly generated cases. The numerical results of are compared with those of a reference model that excludes outsourcing. The comparative findings show the importance of outsourcing, and highlight its substantial potential in reducing a company's production costs.