A computerized model for the selection of materials handling equipment and area placement evaluation (SHAPE)

Abstract

This research presents a construction algorithm for solving the facilities design problem which is the joint solution of a plant layout problem and a materials handling equipment selection problem. The emphasis in this research is on solving each component subproblem rather than on resolving their dependency on one another. The plant layout problem is formulated as a generalized assignment problem whose objective is minimizing the movement cost. The solution algorithm is a heuristic that utilizes the solution procedure of locating one item in a warehouse repetitively in placing and constructing the departments, thus allowing the objective function of the model to affect departmental shapes, and vice versa. The main features of the plant layout algorithm are: (1) It selects the departments to enter the layout according to the sum of major flow values. (2) It eliminates the scale and its undesirable effects by expressing departmental areas as unit squares. (3) It provides, as much as possible, regular and near optimal shaped departments and layout outline without prespecifying any particular shapes. The materials handling equipment selection problem is formulated as integer program with the objective being to minimize the total operating and investment costs of the selected equipment. Each move is allowed to be performed by only one equipment type and the available operating time of each equipment type cannot be exceeded. The problem is solved by a heuristic algorithm that exploits, conceptually, its similarity to both the knapsack and the loading problems. The algorithm is computationally attractive and helps achieve other goals of the problem such as maximizing equipment utilization and minimizing the variations in their types. The algorithm is termed SHAPE (Selection of Materials Handling Equipment and Area Placement Evaluation) and is coded in FORTRAN-IV. The layout problem is first solved and the distances between the departments are utilized in calculating the operating times and costs of the moves. Finally, the selection of the equipment and their assignment to the moves are accomplished.