Job shop scheduling with group-dependent setups, finite buffers, and long time horizon

The design and implementation of a scheduling system for the manufacturing of Toshiba's gas insulated switchgears is presented. The manufacturing is characterized by significant machine setup times, strict local buffer capacities, the option of choosing a few exclusive-or routes for processing, and long horizon as compared to the time resolution required. Our goal is to obtain near optimal schedules with quantifiable quality in a computationally efficient manner. To achieve this goal, a novel integer optimization formulation with a separable structure is developed and a solution methodology based on a combined Lagrangian relaxation technique and heuristics is developed. The method has been implemented using the object-oriented programming language C++, and preliminary testing results show that effective schedules can be efficiently generated while considering the special features.