Designing Flexible Mixed-Product Lines Using a Search Method

Abstract

This paper presents a method for designing flexible mixed-product lines. The word "flexible" means product-mix flexibility. The flexible mixed-product line executes various production plans. Each production plan represents the quantity scheduled to assemble each product type in a time period. Our design method consists of a search method for solving the design problem on flexible mixed-product lines. This method searches out a solution of the design problem by assigning tasks (elemental work) to each workstation and selecting a kind of subject (worker, robot, equipment or combination of those) and kinds of tools to perform the tasks assigned to each workstation. This design method requires the following data and information. (1) The product types to be assembled on the same line. (2) The various production plans to be executed. (3) The precedence diagram of each product type and the combined precedence diagram. Kinds of subjects and kinds of tools able to perform each task and performance times are written in the diagram. A combination of the subject and the tool able to perform a task determines the task performance time. This design method adopts the goal of minimizing the number of workstations to execute each production plan under a time period. To attain the goal, this design method utilizes a composite lower bound, but is not a branch and bound method. The validity of this method was confirmed by solving many problems. The solutions were mainly assessed by the following criteria. (1) Whether or not the number of workstations on the line that is designed by this method is minimized. (2) Whether or not the design suggested by this method is efficient.