A design methodology for fractal layout organization

This paper proposes a methodology for designing job shops under the fractal layout organization that has been introduced as an alternative to the more traditional function and product organizations. We first begin with an illustration of how a fractal job shop is constituted from individual fractal cells. We then consider joint assignment of products and their processing requirements to fractal cells, the layout of workstation replicates in a fractal cell and the layout of cells with respect to each other. The main challenge in assigning flow to workstation replicates is that flow assignment is in itself a layout dependent decision problem. We confront this dilemma by proposing an iterative algorithm that updates layouts depending on flow assignments, and flow assignments based on layout. The proposed heuristic is computationally feasible as evidenced by our experience with test problems taken from the literature. We conclude by showing how the methodologies developed in this paper have helped us evaluate fractal job shop designs through specification of fractal cells, assignment of processing requirements to workstation replicates, and development of processor level layouts. This step has had the far-reaching consequence of demonstrating the viability and the validity of the fractal layout organization.     

Genetically assisted optimization of cell layout and material flow path skeleton

A continuous plane manufacturing cell layout and intercell flow path skeleton problem formulation involving rectilinear distances between cell input/output stations is mapped to a genetic search space. Certain properties of such a search space are exploited to design a very efficient method for reduction of a mixed-integer programming problem formulation to an iterative sequence of linear programming problems. This paper reports theoretical and computational insights for efficiently finding good solutions for the above problem formulation, taking advantage of the solution structure and the search stage. The scores of the objective function on a set of test cases indicate better solutions than those previously reported in the literature. The empirical results based on multiple runs also suggest that the method generates final results that are not dependent on the quality of the initial solution; hence the solution search seems to be more global than many of the previous approaches.