Facility Layout

1
CHAPTER 11

Facility Layout
2
Learning Objectives

1. 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.
2. Explain the layout for a continuous flow process
   and why it is dominated by precedence
   relationships.
3. Explain the important issues in laying out an
   assembly line, and describe the need to balance
   workloads on an assembly line.
4. Describe the relationship between the capacity of
   an assembly line and its cycle time.
5. Balance a simple assembly line and understand the
   role of computers in assembly line balancing.
6. Explain the problems of motivating assembly-line
   workers and describe some possibilities for
   improving motivation.
7. Describe techniques for building families of
   parts used in manufacturing cells and flexible
   manufacturing systems.
8. Construct a model of the job shop layout problem
   and apply techniques for developing a layout.
9. 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
Continuous flow shop Sorting mail U.S. Postal Service sorts millions of pieces of bulk mail daily Making paper Longview Fiber transforms trees into wood pulp, continuously Transaction processing Citibank processes checks, Amazon processes customer orders, Federal Government processes FAFSA (financial aid forms)
Assembly lines Automobiles DaimlerChrysler assembles automobiles Food preparation DiGiorno's assembles frozen pizza for your supermarkets Microcomputers Gateway assemble personal computers
6
Some Examples of the Layout Criteria -- Continued
Batch Medicine Merck create a variety of medicines in large batches using the same equipment Surgery Shouldice Hospital specializes in hernia surgery Lumber Weyerhauser cures lumber in specially design kilns (furnaces)
Manufacturing Cells and Flexible Manufacturing Systems Metal forming operations Wyman-Gordon forges many different parts for the automotive industry Hospitals services Hospital wards group together patients with similar needs to improve service and lower costs
Job Shop Offices Colleges of Business strive to achieve a layout that locates colleagues with similar interests close together Medical services Emergency room layouts cope with a wide variety of medical problems
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
Workstation 1 Workstation 2 Workstation 3 Workstation 4
Tasks A B, C D, E F
Time 60 120 90 90
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
A Balanced Assembly Line
Workstation 1 Workstation 2 Workstation 3 Workstation 4
Tasks A, B C D, E F
Time 90 90 90 90
18
Introduction to Balancing the Line
19
Relation of Capacityto Cycle Time
20
Selecting a Cycle Time Determines System Capacity
Max.(ti) Cycle time Sti Capacity (PR)H

21
Example

• Farmalls 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 rules are 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 principles guide the layout in batch
  operations? Efforts should be directed at
• (1) combining products with similar processing
  requirements
• (2) using the same or a similar sequence 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
Packs Packs Packs Packs Packs Packs
Machine Code A B C D E F
01 1 1 1
02 1 1 1 1
03 1 1 1 1
04 1 1
05 1 1 1
Packs Packs Packs Packs Packs Packs
Machine Code D A C B F E
01 1 1 1
02 1 1 1 1
03 1 1 1 1
04 1 1
05 1 1 1
36
Quadrum Corporations ExistingJob Shop Layout
37
Quadrum Corporations 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
Transparency 11.18
(Exhibit 11.10)
49
Finding an Initial Layout
50
Facility Layout forEqually Sized Departments
51
The Adjacent-Department Method

• The assumptions of the adjacent-department
  method
• -the cost per unit distance is equal for all
  trips
• -departments can be categorized as adjacent
• This simplifying assumption permits the user to
  make quick judgments about the positioning of
  departments and to make relatively few
  calculations.

52
Job Shop Activity Matrix Representing
TripsBetween Departments
53
Ranked Activity Levels
54
Partial Layout
55
Layout
56
Evaluation
57
Facility Layout forEqually Sized Departments
58
Value of Layout
Activity Level (A )
Distance (D )
Department Pair
Cost (C )
(A)(C)(D)
(A)(C)
lj
lj
lj
25 50 30 70 100 20 35 50 30 70 80 20 20 10 40
1 /ft. 1 1.5 1 1 2 1 2 1 1 1 1.5 2 1 1
25 50 45 70 100 40 35 100 30 70 80 30 40 10 40
A-B A-C A-D A-E A-F B-C B-D B-E B-F C-D C-E C-F D-
E D-F E-F
47.2 25 40 47.2 40 40 25 80 83.8 47.2 40 47.2 83.8
80 25
1,180 1,250 1,800 3,304 4,000 1,600 875 8,000 2,51
4 3,304 3,200 1,416 3,352 800 1,000 37,595
59
Generating a Better Solution

• The steps of Generating a Better Solution
• - Determining An initial solution and the
• value of that initial solution
• - The next task is to find a way to improve
• the situation

60
Revised Facility Layout for Equally Sized
Departments
61
Value of Revised Layout
Activity Level (A )
Distance (D )
Department Pair
Cost (C )
(A)(C)(D)
(A)(C)
lj
lj
lj
25 50 30 70 100 20 35 50 30 70 80 20 20 10 40
1 /ft. 1 1.5 1 1 2 1 2 1 1 1 1.5 2 1 1
25 50 45 70 100 40 35 100 30 70 80 30 40 10 40
A-B A-C A-D A-E A-F B-C B-D B-E B-F C-D C-E C-F D-
E D-F E-F
47.2 47.2 40 25 40 80 25 40 83.8 83.8 40 25 47.2 8
0 47.2
1,180 2,360 1,800 1,750 4,000 3,200 875 4,000 2,51
4 5,866 3,200 750 1,888 800 1,888 36,071
62
Stopping Rules

• Stopping rules are more difficult than manually
  solved problems. Stopping rules for
  computer-based solutions are easier to define and
  will be discussed in a later section.

63
Modeling Layouts with Departments of Unequal Size

• The first is to draw the layouts to scale and
  then measure distances from center to center,
  using a ruler.
• The second approach is to cut pieces of paper to
  scale and quickly and easily move them around to
  make new layouts.

64
The Role of Computers in Job Shop Layout

• Specify a certain amount of computer time, and
  use the best solution found.
• Allow the model to perform the switching of pairs
  only a certain number of times.
• Specify an increment of improvement to be
  achieved with each evaluation. If this is not
  achieved, the procedure will end.
• Combine some of these rules.

65
Computer-Based Procedures

• Computerized Facility Design (COFAD)
• Plant Layout Analysis and Evaluation Technique
  (PLANET)
• Computerized Relationship Layout Planning
  (CORELAP)
• Automated Layout Design Programs (ALDEP)

66
Systematic Layout Planning

• The definition of Systematic layout planning
  (SLP)
• The solution procedure
• Using a simple evaluation procedure to judge the
  effectiveness of the solution

67
Information for Systematic Layout Planning for a
Machine Shop
68
Solution and Evaluation of a Machine Shop Layout
69
Using Layout for Competitive Advantage

• A good layout impacts an organization's
  performance.
• Layout decisions should be made only after
  consideration of the long-term impact on the
  overall facility.
• How will future options be affected if a change
  is made in layout?