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Ch 7 - Facilities

  1. Introduction (p259)
    1. Def - Facility layout - arranging departments, processes, machines, workstations, and support services for effective and efficient production.
    2. *Objective - minimize total cost of:
      1. Materials handling
      2. Communication (face-to-face)
      3. Safety risks
      4. Flexibility for new products.
    3. Some reasons for layout analysis
      1. New facility
      2. New process (Internet, intranets)
      3. New products
      4. Volume changes.
  2. Basic Layouts
    1. Process (functional) layout - groups similar activities together according to the process or function they perform.
      1. Used with an intermittent process (Defined Ch6 II.B).
      2. Examples - department store (Fig 7.1), machine shop (Fig 7.2), most offices
    2. Product layout - groups activities by the sequence of tasks required to assemble the product.
      1. Used with repetitive or continuous process (Defined Ch6 II.C and D).
      2. Examples - assembly line for cars, continuous production of glass, repetitive services (processing insurance claims)
    3. Fixed-position layout - groups activities by the limited storage areas around the product.
      1. Used for large, bulky products that require Project Management (Ch 9) (Defined Ch6 II.A).
      2. Examples - ships, buildings, aircraft.
  3. Designing Process Layouts (p264)
    1. *Block Diagramming
      1. Input data
        1. Load Summary Chart - p265
        2. Space required for each department
      2. Objective - assign departments to rooms so that nonadjacent loads are minimized. A nonadjacent load is between rooms farther than the next block, either horizontally, vertically, or diagonally.
      3. Example 7.1 - p265
        1. Determine Composite Movements
        2. Evaluate potential layout - Grid 1 - 150 nonadjacent loads
        3. If some nonadjacent loads, try to reduce - Grid 2 - 0 nonadjacent loads
      4. Develop Final Block Diagram by adjusting departmental space requirements to shape of the building - Fig 7.4
                Do assigned HW - Problem 7-4.
    2. *Computer Packages for Process Layout
      1. Heuristic programs - CRAFT, …
      2. Simulation software - PROMODEL, …
      3. Quadratic programming - gives optimal solution but present algorithms can solve only small problems.
  4. Designing Product Layouts (p271)
    1. *Line Balancing
      1. Input data
        1. Tasks
        2. Task times - times to perform each task
        3. Precedence requirements - tasks which must be completed before another task can start
        4. Cycle time - length of time the product is at each work station
      2. Objective - assign tasks to work stations so as to minimize the number of work stations.
      3. Example 7.2 - p273
      4. Heuristic Procedure
        1. Draw Precedence Diagram
        2. Compute cycle time = (production time available) / (desired units of output)
                      = 40*60/6000 = .4 minutes
        3. Assign tasks to work stations   (Note: different from page 273.)
          1. Determine Available List - tasks whose precedence requirements are satisfied.
          2. Select from the Available List the task with the largest possible time such that for each work station: sum of task times £ cycle time
          3. Update the Available List
          4. Repeat until all tasks are assigned.
        Available 
        List        		 Selected 
        Task        		   Time   Work
        Station  
          A
          B, C        		   A
          B        		   .1
          .2        		    1
           1
          C   C   .4    2
          D   D   .3    3
      5. Optimality test
        1. m - minimum number of work stations
        2. m = S ti / cycle time              (rounded up, not rounded off)
        3. m = 1.0/0.4 = 2.5 rounded up to 3
        4. The above heuristic solution with 3 work stations is optimal because it is not possible to have a solution with fewer than m work stations.
                  Do assigned HW - Problem 7-22.
  5. Hybrid Layouts (p275)
    1. *Cellular Layout - groups dissimilar machines into work cells that process parts with similar shapes or processing requirements, Fig 7.8a, p276.
      1. Improves the efficiency of a process layout, while maintaining some flexibility. See Figs. 7.9, 10, 11.
    2. *Mixed-Model Assembly Line - produces more than one model, p281.
      1. Improves the flexibility of a product layout, while maintaining some efficiency.
  6. Site Selection (Chapter 7 Supplement, page 296)
    1. Global Location Factors
      1. Government stability, tariffs, …
      2. Economy, exchange rates
      3. Culture
    2. Regional Location Factors
      1. Government regulations (environmental), taxes, incentives
      2. Proximity of customers and suppliers
      3. Availability and cost of labor, raw materials
      4. Infrastructure (roads, water, sewers, utilities)
    3. Site Location Factors
      1. Site size and cost
      2. Local attitudes, zoning
      3. Access to roads, rail, shipping
  7. Factor Rating Method with Ben Franklin's Prudential Algebra (p300)
    1. *Procedure -  Click here for details - www.patlyons.com/research/PrudentialAlgebra.htm 
      1. Assign a weight, wi , to each factor to reflect its importance, so that  å wi = 1.
      2. Assign a score, si j , for each location and each factor, so that  si j  is between 0 and 100.
      3. Sum wi si j for each location.
      4. Select the site with the highest sum as the best candidate.
      5. Form a comparison matrix by subtracting each site’s wi si j from the best candidate’s wi si j .
      6. Qualitatively compare each site with the best candidate using the least number of positive factors to outweigh all negative factors.
      7. Conclude that best candidate is best or revise weights and scores.
    2. Example S7.1 - p300 - location for a ring bearing plant.
           Score
    Factor

     Weight 

      Site1 

      Site2 

      Site3 

    Labor pool 0.30   80   65   90
    Prox. Suppliers 0.20 100   91   75
    Wage rates 0.15   60   95   72
    Community 0.15   75   80   80
    Prox. Customers   0.10   65   90   95
    Shipping modes 0.05   85   92   65
    Air service 0.05   50   65   90

     

      a. Weighted scores b. Comparison
    Factor    Site1     Site2     Site3    Site3-Site1   Site3-Site2
    Labor pool 24.00 19.50 27.00    3.00    7.50
    Prox. suppliers 20.00 18.20 15.00   -5.00   -3.20
    Wage rates   9.00 14.25 10.80    1.80   -3.45
    Community 11.25 12.00 12.00    0.75    0.00
    Prox. customers      6.50   9.00   9.50    3.00    0.50
    Shipping modes   4.25   4.60   3.25   -1.00   -1.35
    Air service   2.50   3.25   4.50    2.00    1.25
      77.50 80.80 82.05    

    Site 3's (best candidate) favorable
            Labor pool,
            Proximity to customers, and
            Air service
        outweigh Site 1's favorable
            Proximity to suppliers, and
            Shipping modes.

    Site 3's favorable
            Labor pool, and
            Air service
        outweigh Site 2's favorable
            Proximity to suppliers,
            Wage rates, and
            Shipping modes.

    Therefore, Site 3 is the best.

    Do assigned HW - Problem S7-1. 
                                                     (This page was last edited on August 30, 2006 .)