Computation Section
Subunit Facility Layout
 -Defining the Facility

The button on the Layout Data worksheet presents the dialog box shown below with which the various solution options are selected. The distance between two departments is the distance between their respective centroids. When material movement is parallel to the length and width boundaries of the plant, it is reasonable to use the rectilinear measure. When the movement is via straight lines between the two centroids, the Euclidean measure is appropriate. Two solution options are available, the Optimum Sequence method and the Traditional Craft. We first discuss the Optimum Sequence method. The length and width of the plant and the aisle width are set in the fields at the bottom.


The facility layout worksheet has various parameters and options listed at the top of the page as illustrated below. The cells on this worksheet that are colored yellow hold either formulas or data controlled by the program, so they should not be manually changed. The worksheet name should not be changed.

At the top of the page in column B we see the name, number of departments, length and width of the facility, total area and the cost for the current layout (shown in the next figure). We hope to find a layout that minimizes the cost in cell B8. Column E holds parameters that are described subsequently.

Starting in row 11, a row is provided for each department. Column A holds the department name, column B holds its color, column C holds the area defined on the Layout Data worksheet, column D holds the area defined for the department on the current layout. Columns E and F hold the computed centroids of the department. For this example, we are using an Aisle layout. Column G shows the sequence number of the department. The ranges shown in green hold numbers computed by the program.

When the Sequential button is selected for the initial solution, a layout is automatically generated with the departments listed in numerical order in column G. This is the default initial sequence, but the numbers in this column can be changed to accommodate a user-supplied initial sequence. This is important if some departments are given a fixed index in the sequence.

The Leave Blank option is available only with traditional craft. Here the layout is left blank initially and the user must manually define the department locations in the layout. The layout is immediately to the right of this data on the worksheet.

The initial layout for the example was generated with the default sequence using an Aisle layout and is shown below.


The layout starts in cell J11. The number of colored cells to the right of J11 is the width of the facility and the number of colored cells below J11 is its length. The locations of the departments are specified by department indices or colors. The initial layout can be entered manually or automatically. It is most convenient to use an automatic Aisle layout. The aisles are indicated by the white lines running through the centers of the departments. This layout form is often associated with the ALDEP layout construction procedure.

The aisle layout is determined by the department width, which for the example is equal to 5, and the sequence of departments. For the example we have chosen the sequence as the department indices. The first department in the sequence starts in cell J11 and is assigned cells to the right until the department area is completely defined or the department width is reached. For the example, department 1 requires all five cells. The second department is placed below the first, using as many rows as necessary to enter the entire area. We continue to add departments until the entire length of the facility is used. Then the departments are placed at the bottom of aisle 2. In the example, department 4 uses both aisles 1 and 2. The layout continues up aisle 2 until the top is reached for department 8. The the layout proceeds down aisle 3 until all departments are placed. For the example, five cells remain unused. The white lines on the layout show the serpentine nature of this layout procedure.

To illustrate the effect of a different department width we click the Change button. The dialog below is presented. Any of the options may be changed by clicking a button or changing the fields defining the width and length of the plant and the depth of an aisle. In this case we change the depth to 4.

Because the department areas are not multiples of 4, the layout becomes more irregular. This affects that accuracy of distance measurements since department centroids are no longer in the center of rectangular departments.


An alternative layout that more nearly maintains rectangular departments is obtained when the Full Width box is checked. The result for the example is shown below. For this option, departments are increased in area so that they fill an integral number of rows of the layout. Note that the area of department 1 has increased from 5 to 8. Of course, when department areas are increased, it may be necessary to increase the size of the facility. This is the case for the example where it is necessary to increase the length of the facility to 12 so that the larger departments can be accommodated.


The next step is to search for the optimum layout. We consider first the Optimum Sequence method and then the Traditional Craft method on the following pages.

Return to Top

tree roots

Operations Management / Industrial Engineering
by Paul A. Jensen
Copyright 2004 - All rights reserved