A linear programming model for optimal subassembly level determination in shipbuilding industry

Shipbuilding industry is an industrial sector characterized by a customized make-to-order production process. The shipbuilding process can be roughly divided into four steps: design, assembly planning, manufacturing and final assembly. In this paper assembly planning is investigated: it consists in subdividing the ship structure into blocks and grand-blocks, thus involving a two levels subassembly generation. Any mechanical assembly process can be decomposed into a set of tasks, each task involving joining two or more components or subassemblies together. The sequence of assembly tasks has a major influence on completion time and resource utilization and it drastically impacts costs and efficiency through the whole production process. To determine the optimal assembly policy and subassembly level a Linear Programming model is proposed. The model allows the determination of the optimal block grouping policy, in order to minimize the total assembly time or to achieve workload balancing.