Off-site construction optimization: sequencing multiple job classes with time constraints

Off-site construction is a unique hybrid of manufacturing operations and on-site construction activities. Maximizing the production output has long been the main challenge for off-site manufacturers. Among other responses to this challenge, the use of multi-task shared resources has proved its effectiveness in improving tangible performance measures of production. However, multi-skilled resources often become bottlenecks (overloaded) when producing multiple classes of products and prevent the production network from meeting due dates. This paper analytically models the problem of defining the optimal product sequencing using optimization-based metaheuristics with the aim of minimizing changeover time, which is wasted switching from a product class to another. Production data of two Australian off-site manufacturers are used in the subsequent empirical analysis resulting in advancement of five research propositions. This research contributes to the scheduling theory by expanding the insight into dynamics of resource sharing and job sequencing. The developed models and propositions are of practical value for off-site manufacturers of building elements to maximize their production output.