DESIGN OF PROCESS LAYOUT - Production and Operations Management

The analysis involved in the design of production lines and assembly lines relates primarily to timing, coordination, and balance among individual stages in the process.For process layouts, the relative arrangement of departments and machines is the critical factor because of the large amount of transportation and handling involved.


Process Layout Design in Operations Management

Process layout design determines the best relative locations of functional work centers. Work centers that interact frequently, with movement of material or people, should be located close together, whereas those that have little interaction can be spatially separated. One approach of designing an efficient functional layout is described below.

  1. List and describe each functional work centre.
  2. Obtain a drawing and description of the facility being designed.
  3. Identify and estimate the amount of material and personnel flow among work centers
  4. Use structured analytical methods to obtain a good general layout.
  5. Evaluate and modify the layout, incorporating details such as machine orientation, storage area location, and equipment access.

The first step in the layout process is to identify and describe each work centre. The description should include the primary function of the work centre; drilling, new accounts, or cashier; its major components, including equipment and number of personnel; and the space required. The description should also include any special access needs (such as access to running water or an elevator) or restrictions (it must be in a clean area or away from heat).

For a new facility, the spatial configuration of the work centers and the size and shape of the facility are determined simultaneously. Determining the locations of special structures and fixtures such as elevators, loading docks, and bathrooms becomes part of the layout process.

However, in many cases the facility and its characteristics are a given. In these situations, it is necessary to obtain a drawing of the facility being designed, including shape and dimensions, locations of fixed structures, and restrictions on activities, such as weight limits on certain parts of a floor or foundation.

Relationship flow diagram

Relationship flow diagram

To minimize transport times and material-handling costs, we would like to place close together those work centers that have the greatest flow of materials and people between them. To estimate the flows between work centers, it is helpful to begin by drawing relationship diagram as shown in the above figure.

For manufacturing systems, material flows and transporting costs can be estimated reasonably well using historical routings for products or through work sampling techniques applied to workers or jobs. The flow of people, especially in a service system such as a business office or a university administration building, may be difficult to estimate precisely, although work sampling can be used to obtain rough estimates.

The amounts and/or costs of flows among work centers are usually presented using a flow matrix, a flow-cost matrix, or a proximity chart.

  1. Flow Matrix
    A flow matrix is a matrix of the estimated amounts of flow between each pair of work centers. The flow may be materials (expressed as the number of loads transported) or people who move between centers. Each work centre corresponds to one row and one column, and the element fij designates the amount of flow from work centre (row) I to work centre (column) Normally, the direction of flow between work centers is not important, only the total amount, so fij and fji can be combined and the flows represented using only the upper right half of a matrix.
  2. Flow Matrix Table

    Flow Matrix Table

  3. Flow-cost Matrix
    A basic assumption of facility layout is that the cost of moving materials or people between work centers is a function of distance travelled. Although more complicated cost functions can be accommodated, often we assume that the per unit cost of material and personnel flows between work centers is proportional to the distance between the centers. So for each type of flow between each pair of departments, i and j, we estimate the cost per unit per unit distance, cij
  4. Flow-cost Matrix Table

    Flow-cost Matrix Table

  5. Proximity Chart
    Proximity charts (relationship charts) are distinguished from flow and flow-cost matrices by the fact that they describe qualitatively the desirability or need for work centers to be close together, rather than providing quantitative measures of flow and cost. These charts are used when it is difficult to measure or estimate precise amounts or costs of flow among work centers.
    This is common when the primary flows involve people and do not have a direct cost but rather an indirect cost, such as when employees in a corporate headquarters move among departments (payroll, printing, information systems) to carry out their work.

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Production and Operations Management Topics