A well known automated procedure for searching for the optimum is called the CRAFT method. The method tries to improve an initial layout by switching the locations of department. Candidates for switching are pairs of departments that have the same area or pairs of departments that are adjacent in the layout. Switching departments that are not adjacent and that have different areas would obviously result in non-contiguous departments. The diagrams and computations illustrated below were provided by the Layout add-in. We begin with the aisle layout determined by the sequence {1, 2, … , 10} and an aisle width of 5.

To illustrate department switches, consider the feasible switches that involve department 6 in the layout above. Departments 2 and 8 have the same area, so the pairs (2, 6) and (6, 8) are feasible. Departments that are adjacent to 6 are departments 3, 5, 7, 9 and 10, so the pairs involving these departments and department 6 are also feasible.

To evaluate the effect of switching the two departments, the CRAFT method assumes that the centroids of the two departments are switched and computes the resultant cost savings. Switching the centroids of the two departments is equivalent to switching the interdepartmental distances involving the two departments. The entire layout need not be evaluated, but only the terms involving the two departments as shown below for the general switch of departments k and l.

For a given layout we evaluate the effects of all feasible departmental switches and choose the one with the most negative value of . If there are no negative values, the process terminates. When the two departments are the same size, this evaluation is accurate. When the departments have different sizes, the centroids of the departments do not exactly switch locations. In this case the evaluation may be not be accurate and a switch that looks promising may actually increase the cost of the layout. The CRAFT method implemented by the add-in terminates if this occurs.

For the example, the best feasible pair is 9 and 10. Since the two departments are different sizes, there are many alternatives for arranging the cells of the smaller sized department 9 into the larger area formerly holding department 10. The Layout add-in has an algorithm for choosing the arrangement that results in the layout below. Although one might question the logic of this arrangement, it is difficult to program an algorithm that always makes the assignment that would appear most reasonable to the human designer. The objective value for the changed layout is shown above the upper-left corner in the figure below. The layout has an improved objective compared to the initial solution.

The next iteration switches departments 2 and 3.

The next iteration switches departments 2 and 5.

The program next estimates that if the centroids of departments 7 and 8 are switched, the cost of the layout will be reduced. When the switch is actually made, the cost increases. This occurs because the centroids used by the evaluation are quite different than the centroids after the departments are switched. The CRAFT method must terminate at this point because no improving switches are available.

The results of the CRAFT method depend on the initial solution and the sequence of switches performed. The add-in generates random initial solutions, so better solutions may be found by repeating the process for different random initial solutions. The results are often not very satisfactory for problems with departments of different sizes. As in the example, the final layout has departments far from the desired rectangular shape. It is even possible that departments may be split into sets of non-adjacent cells.