Product due date assignment for complex assemblies

A method is described to assign product due dates for multistage assemblies with uncertain manufacturing and assembly process times. Earliest start times of operations are specified by a predetermined production plan and processing time distributions for operations are truncated at minimum processing times. The method systematically decomposes the complex product structures of multistage assemblies into two-stage subsystems. Both exact and approximate distributions of completion time for two-stage assemblies are developed. The latter is applied recursively to multistage assemblies to yield an approximate distribution of product completion time. Product due dates are assigned to either minimise earliness and tardiness costs or to meet a service target. This method is applied to examples which use manufacturing and assembly data from a capital goods company. The results are verified by simulation.