A production scheduling method was proposed for injection molding(IM) process with multiple products produced by a single machine

in order to achieve global minimum energy consumption.The total energy consumption was split into three parts.The first part was defined as switchover energy consumption

i.e.

the energy used for replacing the die and mold

changing the color or material

etc.The second part was defined as transitional energy consumption

which was determined by the regulation time for controlling the end-product with desired quality.The third part was the energy consumed during the stable production periods

which was defined as stable energy consumption.The total energy consumption model was described by a directed graph

where the nodes represented the stable production of different products and the arcs represented product switchovers.The single-machine-multi-product scheduling problem was formulated as a typical traveling salesman problem(TSP).A genetic algorithm(GA) based lexicographic optimization framework was proposed to solve such a scheduling problem.The first-layer optimization was to search the feasible process parameters that contributed to reliable production of each product.The second-layer optimization was to solve a TSP problem by finding the optimal switching path among the multiple products in order to minimize the global energy consumption. The proposed scheduling method could improve production efficiency and reduce energy consumption. Experimental results in laboratory scale tests demonstrated its feasibility and effectiveness.