Energy-Efficient Parallel Batching of Jobs with Unequal and Undefined Job Sizes on Parallel Batch Processing Machines

This paper investigates a parallel batching problem with incompatible families, unequal job sizes and non-identical machine capacities. The objective is to minimize the total energy costs. Motivated by a real-word autoclave molding process in composite material manufacturing additional factors need to be considered: machine eligibility conditions, machine availability constraints, machine dependent energy consumption, and the job size and machine capacity may not be available in absolute terms. Mathematical models are formulated for both defined and undefined job and machine sizes. The latter approach creates batches based on a set of best-known batches derived from past production data to meet the machine capacity constraint. Finally, a heuristic is presented. Computational experiments are conducted based on a real case study. Energy savings of over 20 % can be achieved compared to the actual planning with sensible batch forming and machine allocation in a short amount of computing time.