Worker allocation in make-to-order assembly cells

Assembly in the make-to-order manufacturing of large variable products is usually organized as a cell in which a team of workers operates. Several products are assembled in parallel and in sequence, so that the number of workers assembling a product may vary. The release times and due dates of products are determined by a higher level production plan. It is important to meet the due dates and use the workforce efficiently. The objective of the study described here is to optimize the allocation of workers to the products, so that the timing constraints are met, while the labor costs are minimized. Although the number of workers assembling a product can be varied, changing it involves start-up costs while the workers familiarize themselves with a new job, and a suboptimal number of workers reduce the productivity of work. These work efficiency characteristics are implemented in the optimization model presented. The developed model is a mixed integer linear program. The characteristics of the model are discussed and illustrative solutions and experimental results are provided.