Scheduling for two-stage production system with setup and assembly operations

Scheduling for two-stage production system including machining operations, setup operations and assembly operations is addressed, where a number of products of the same kind are produced. Each product is assembled with a set of several parts. The first stage is a single machine to produce parts. It can process all kinds of parts but can process only one part at the same time. Setup operation and setup time are needed when the machine starts processing or when the machine changes items (kinds) of parts. The second stage is a single assembly machine or a single assembly team of workers. The objective function is the mean completion time for all products. Machining operations, setup operations and assembly operations are partitioned into several blocks. Each block consists of the machining operations, the setup operations and the assembly operation(s) for one or several products. Parts of the same kind in a block are processed successively. We consider a problem to partition the operations into blocks and sequence the parts in each block so as to minimize the objective function. A solution procedure using pseudo-dynamic programming is proposed to obtain a near-optimal schedule. A tight lower bound is developed to evaluate the accuracy of the near-optimal schedule. Computational experiments are provided to evaluate the performance of the solution procedure. It has been found that a good near-optimal schedule is obtained efficiently by the proposed solution procedure.