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CHAPTER 11

CHAPTER 11. Facility Layout. Learning Objectives. Illustrate the objectives of the layout decision for a continuous flow process, an assembly line, a batch process, a manufacturing cell, a flexible manufacturing system, and a job shop.

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CHAPTER 11

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  1. CHAPTER 11 Facility Layout

  2. Learning Objectives • Illustrate the objectives of the layout decision for a continuous flow process, an assembly line, a batch process, a manufacturing cell, a flexible manufacturing system, and a job shop. • Explain the layout for a continuous flow process and why it is dominated by precedence relationships. • Explain the important issues in laying out an assembly line, and describe the need to balance workloads on an assembly line. • Describe the relationship between the capacity of an assembly line and its cycle time. • Balance a simple assembly line and understand the role of computers in assembly line balancing. • Explain the problems of motivating assembly-line workers and describe some possibilities for improving motivation. • Describe techniques for building families of parts used in manufacturing cells and flexible manufacturing systems. • Construct a model of the job shop layout problem and apply techniques for developing a layout. • Explain the role of computers in determining a job shop layout.

  3. General Topics In Chapter • Criteria for the Layout Decision • Overview of the Layout Question • Continuous Flow Processes • Assembly Lines • Using Group Technology to Organize Manufacturing Cells and Flexible Manufacturing Systems • Batch Processing • Job Shops • Using Layout for Competitive Advantage

  4. Facility Layout • Facility Layout is the arrangement of work space • Level 1: Where departments or work groups are located with respect to each other • Level 2: How a department is arranged internally • Level 3: How individual work spaces are arranged

  5. Some Examples of the Layout Criteria

  6. Some Examples of the Layout Criteria -- Continued

  7. Continuous Flow Processes • Continuous Flow Processes and Service Industries • Assembly Lines

  8. Continuous Flow Processes and Service Industries • Many continuous flow operations are found in the production of goods • There are some notable exceptions • Examples: The U.S. Postal Service Federal Express Large banks

  9. Assembly Lines • Definition • The purpose of an assembly line • The components of An assembly line

  10. Objectives • First, to lower material-handling costs, the line should be positioned for a continuous flow of assembled products. • Second, the assembly line should have balance in the same way that the continuous flow process has balance.

  11. Example

  12. Example

  13. Results of the Assignment • Cycle time • System cycle time

  14. Calculating Production Rate From Cycle Time

  15. Calculating Idle Time The sum of the idle times at each station is the idle time in the system.

  16. Calculating Unit Labor Cost The total labor cost for eight hours is (8 hours/shift) (4 workers/shift) ($20/hour), or $640/shift. The total number of units produced is (30 units/hour) (8 hours/shift), or 240 units/shift. The unit cost is ($640/shift) (240 units/shift), or $2.67/unit.

  17. Unbalanced Line Balanced Line Total task time 360 seconds 360 seconds Cycle time 120 seconds 90 seconds Production rate 30 units/hr. 40 units/hr. Idle time 120 seconds/unit 0 Unit cost $2.67/unit $2.00/unit A Balanced Assembly Line

  18. Introduction to Balancing the Line

  19. Relation of Capacityto Cycle Time

  20. Selecting a Cycle Time Determines System Capacity Max.(ti) ≤ Cycle time ≤ Σti Capacity = (PR)H ­

  21. Example • Farmall’s Clarkson plant assembles a modulator to control water flow. This unit has a forecasted demand of 15,000 units per month. • Even though demand is highly seasonal, Farmall has decided to balance its assembly line to produce 400 units during a forty-hour week.

  22. Example -- Continued ­

  23. Example -- Continued

  24. Medical Kit Example

  25. Techniques for Assembly-line Balancing A few of the simplest choice rulesare listed here: • Longest task time • First in the list • Most following tasks

  26. Example The facility manager has been directed to balance this single-line operation with one forty-hour shift. The line should produce 6,000 kits per week.

  27. Example -- Continued

  28. Balanced Line for theMedical Kit Problem Time remaining at the Station (Seconds) Task Selected Assigned to Station Task Available to be Scheduled 1 1 2 2 2 3 3 4 4 5 0 3 0 7 3 A B,C,D C,D C E F,G,H G,H H I J A B D C E F G H I J

  29. Example

  30. The Role of Computers in Balancing the Line • Computer models can keep track of all the details in the procedure and can be run quickly with a variety of cycle times and selection methods. • use more complicated procedures for selecting tasks from the available list. • The Computer Method of Sequencing Operations for Assembly Lines (COM-SOAL) rapidly generates large numbers of feasible solutions that can quickly be evaluated to determine which one gives the best balance.

  31. Motivation • Money is not the answer. The average wage paid by the U.S. automakers is higher than the average wage paid at the assembly facilities owned by the Japanese in the United States. The motivation of the U.S. workers in the Japanese transplants is as high or higher than the motivation of the U.S. workers. • Employees should be encouraged to think about ways to solve problems related to their job and to improve plant operations. • Labor-management relationships are a key to effective use of employees in problem solving.

  32. Batch Processing What principlesguide the layout in batch operations? Efforts should be directed at: (1) combining products with similar processing requirements (2) using the same or a similarsequence of operations.

  33. Using Group Technology to Organize Manufacturing Cells and Flexible Manufacturing Systems • GT is an approach to manufacturing based on the idea of grouping similar parts into families economies in manufacturing cycle

  34. Methods for Creating Families of Parts • Visual inspection (tacit judgment) • Product flow analysis (PFA)

  35. Example

  36. Quadrum Corporation’s ExistingJob Shop Layout

  37. Quadrum Corporation’s Proposed Layout for Transmission Parts

  38. Job Shops • The limitation of using job shops • The steps in approaching the job shop layout problem • In most real job shop problems, the product flow is not completely random

  39. Activity Matrices for a Dominant and a Random Product Flow

  40. Activity Matrices for a Dominant and a Random Product Flow -- Continued

  41. Activity Matrix for the Rieselinger Research Institute

  42. Finding the Pattern and Determining the Layout To model the layout question in a job shop and find the hidden pattern, the objective of the layout should be well defined.

  43. Objectives • Aij = the activity level from department i to department j; i = 1, …, n, and j = 1, …, n, where n is the number of department • Dij = the distance from department i to department j • Cij = the cost per unit distance from department i to department j

  44. Activity Data • If this is an existing facility, records of past jobs and the movements between departments should be available. • If records do not exist, the present set of jobs and future jobs can be used to build the activity matrix­. • If it is a new facility, estimates of the activity levels can be generated from the types of jobs expected in the facility. • What-if analysis can be done by changing the activity levels to reflect a different mix of jobs.

  45. Layout of the Facility • If an existing building is to be used, the analyst should work with a drawing that is to scale. • If a new building is to be constructed, the analyst can work without boundaries to determine the building's shape. Still, working to scale is important.

  46. Estimates of the Costs Per Unit Distance Traveled • Estimates of transportation costs can usually be made from data available in accounting records. • If they cannot be, there are at least two options for the analyst. (1) information from other similar operations can be used to estimate costs. (2) the cost per unit distance can be assumed to be equal for all trips between departments.

  47. Technique for Determining the Layout • Step 1. Determine a feasible initial solution. • Step 2. Evaluate the new solution(s), and keep the best one. Is the solution satisfactory? If so,stop; otherwise, continue with step 3. • Step 3. Change the present solution in an effort to find an improved solution. Return to step 2.

  48. Activity Matrix for the Rieselinger Research Institute (Exhibit 11.10) Transparency 11.18

  49. Finding an Initial Layout

  50. Facility Layout forEqually Sized Departments

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