Automatic generation of production scheduling models in single stage multi-product batch plants: Some examples

This work considers optimal scheduling of a set of orders in a multi-product batch plant with non-identical parallel processing units where the process is single stage. The allocation of orders to the production units was formulated as an MILP problem in continuous time. Starting from the basic model proposed earlier, and adding a new constraint that was missing in previous literature, the new formulation solves the problem with a different objective function which considers the total production time or total production cost of the set of orders, without resorting to the application of any heuristic rules. A special MATLAB program has been developed for automatic creation of the optimization model, which otherwise may be a very time consuming task prone to errors. The formulation has been tested with extensive numerical, as well as one industrial, problems. The results indicate importance of the proposed modifications and effectiveness of the automated generation of the model, and present better solutions for the industrial example considered.